Course Handout - Memory Glossary
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First published online 08:50 GMT 2nd December 2003, Copyright Derek J. Smith (Chartered Engineer). Transfer of copyright to High Tower Consultants Limited 14th January 2010. This version [2.3 - copyright] 09:00 BST 14th June 2018
Introduction - Physical vs Psychological Memory Types
Just as there are many types of building but only a few types of brick, cognitive science can identify many types of knowledge but only three underlying physical memory types, that is to say, memory types which can be pinned down to concrete anatomical or physiological structures and/or processes. The three recognised physical memory types are as follows .....
Structural - Long Term Memory (LTM): This type of memory derives ultimately from networks of neurons wired together by physical neural fibres and organised into "processing modules". It supports a large number of conditioning and knowledge types, and, although it takes some time to establish itself, is then relatively durable. The adjective "long" indicates a lifespan between an hour or two and several decades.
Electrical - Short Term Memory (STM): This type of memory contains transient knowledge, that is to say, information on its way into, or out of, LTM. Physiologically it derives from momentary fluctuations in ionic electrical potential - both spiked and graded - within neurons, whilst psychologically it accounts for the momentary contents of the cognitive system, and, presumably, of the small fraction thereof which is our consciousness. The adjective "short" indicates a lifespan between say a few milliseconds and, say, two or three seconds, although "reverberatory" feedback within or between modules might, on occasion, artificially extend this.
Electrochemical - Medium Term Memory (not usually abbreviated): This type of memory does not contain any knowledge at all, but rather maintains pointers (sometimes called "tags") to recently activated points within LTM. Biologically this "touch-and-glow" ability derives from synaptic sensitisation processes such as "calcium switching" and "second messenger" neurotransmission, and psychologically it is the key to interfacing the electrical and the structural aspects of memory, and thus maintaining the continuity and coherence of thought. The adjective "medium" indicates a period between, say, two or three seconds and one or two hours. [See under protein kinase studies in the body of this glossary.]
An introduction to the concepts and vocabulary of modern memory theory, both physiological and psychological, is given in the boxed glossary below. Non-psychologists may find it useful to begin by looking up perceptual memory, episodic memory, and semantic memory, and newcomers to neuroscience should familiarise themselves firstly with neuroanatomy, and then move on to neurotransmission and synapse.
Mini-Glossary - The Molecular Biology and Psychology of Memory
Ackerman-Banks Neuropsychological Rehabilitation
Abstract Idea: For general memory theory purposes, an abstract idea is the same thing as a concept [but if you want to see the extended philosophical definition, click here].
Abstraction: At the heart of cognition there is really only one fundamental ability, namely that of abstraction. This is the ability to take the essentials out of something, as when spotting perceptual common factors such as pitch and volume (sound) or colour and shape (vision), or the common attributes which identify members of a category (e.g., "predator" or "triangularity"). Readers may gain some idea how quickly abstraction works from the following example of abstraction of rule: just fill in the blank in the following series .....
wo fe wo, li na li, de ko de, ga ti ____
The usual experience is that the recurring pattern is totally apparent by the end of the third triplet, allowing the mind automatically to deliver the answer "ga" as the missing syllable at the end of the fourth. This particular example comes from research by New York University's Gary F. Marcus, who played such material to 7-month-old infants, and found behavioural preferences for rule-consistent sets over rule-inconsistent sets, suggesting that "the ability to learn rules is a fundamental tool in the baby's mind" (Marcus et al, 1999/2003 online). [See now concept.]
Action Potential: [See firstly resting potential.] Having grasped the principles of the neural resting potential, the next question is what would happen should the metabolic pumps in the neural cell membrane stop working momentarily? The answer is that it would drastically disturb the equilibrium which produced that resting potential in the first place. Indeed, it would create a completely different equilibrium state, and particles would move across the membrane until that new equilibrium was reached; and, because those particles are charged, this would constitute a flow of current across the membrane. This is precisely what happens in the phenomenon known as the action potential or neural "spike discharge". When the sodium pumps in the neural cell membrane get switched off by some influence, and for approximately 1 msec. thereafter, sodium ions rush into the cell down their concentration gradient, reversing the internal polarisation of the cell from -70mV to +40mV. This in turn interferes with the resting potential of adjacent areas of membrane and may thus cause propagation of the action potential. Such non-decremental propagation is generally regarded as underlying all long-distance neural conduction. In fact, there are two distinct stages to an action potential, namely depolarisation and repolarisation. Depolarisation refers to the period of sodium ion inrush, and repolarisation to the re-establishment of the resting potential once voltage-dependent gating restarts the sodium pumps. Repolarisation takes a further 1 msec., and momentarily gives an internal cell charge of -75mV, marginally below the normal resting potential (-70mV). This momentary overcompensation is termed hyperpolarisation, and given another few msec. the membrane "settles down" and the cell returns to its resting state.
Action Potential Threshold: The minimum stimulus needed to produce an action potential is known as the "threshold" stimulus (or simply the "threshold"). It is the potential at which voltage-dependant gating turns off the sodium pumps in the neural cell membrane.
Action Schema: One of the proposals of the Norman-Shallice Model of Supervisory Attentional Function. This model regards the basic unit of action as the action schema, a "sensori-motor knowledge structure" (Norman, 1981, p3) "that can control a specific overlearned action or skill such as [.....] doing long division, making breakfast, or finding one's way home from work" (Shallice, 1982, p199). Shallice sees such schemas as being activated in various ways by different aspects of cognition, but especially by other schemas already in progress, and by new perceptual events.
Activities of Daily Living Test (ADL): [See firstly executive function and dysexecutive syndrome.] ADL is a relatively unstructured screening test for possible problems with the forward planning component of human executive function, and, as such, is commonly included as a frontal battery test. ADL testing was developed as an adjunct to the Norman-Shallice Model of Supervisory Attentional Function, and requires the subject to identify and sequence the individual steps in carrying out a typical everyday behaviour such as making a cup of tea or buying a newspaper. Chevignard et al (2000/2003 online) analyse ADL behaviour in terms of Script Theory, and argue that it is insufficient to assess the planning component in isolation. Instead, another basic frontal skill needs to be assessed at the same time, namely the subsequent "monitoring and guiding the execution of the plan". Fortin, Godbout, and Braun (2003/2004 online) give details of menu preparation, grocery shopping, and meal preparation applications of ADL tests, if interested.
ADL: See Activities of Daily Living Test.
Adrenergic Transmitter: A class of neurotransmitters, including adrenaline, noradrenaline, and dopamine. Unlike cholinergic transmitters, they are not broken down during the recovery phase of synaptic transmission. Instead, they are metabolised back into the pre-synaptic membrane for re-use.
Anion: A negatively charged ion.
Antidromic Conduction: The propagation of a neural impulse in the "backwards" direction, that is to say, from a point of stimulation on the axon back towards the cell body. The opposite of orthodromic conduction.
Articulatory Suppression Effect: [See firstly Working Memory Theory.] Reductions in the capacity of the phonological loop when the cognitive system is required to carry out a simultaneous articulatory interference task. Thus Baddeley, Lewis, and Vallar (1984) found a reduction in digit span from seven to five digits when subjects simultaneously repeated a distractor word like "the" during the retention period.
Association: The linking of two concepts within semantic memory, usually by contiguity. The fact that association occurs so readily probably indicates that the power to associate by contiguity is another basic neural process, second only to abstraction in importance, and allowing yet more regularities in the external world - predictable co-occurrences such as <thunder-follows-lightning> - to be detected almost as soon as they start to appear.
Associationism: A philosophical doctrine usually attributed to the works of David Hartley (1705-1757), and predicated upon the assertion that higher states of consciousness emerge from prolonged experience with simpler mental phenomena such as sensations, emotions, and fragmentary memories. Anticipating Hebb's Rule by two full centuries, Hartley argued that sensations which typically occurred together became associated with each other by simple contiguity, resulting in a semantic network memory. [See now encoding.]
Associationist: Follower of Associationism as a philosophical school and set of explanatory principles.
Attentional Cycle [Project Konrad]: One cycle through Konrad's processing hierarchy, from an input (or re-afferent) element to the consequent output element. Perhaps equivalent to one sinusoidal delta wave in the biological nervous system. The period depends in part on whether short-, medium-, or long-loop processing is taking place.
Attentional Failures: Perceptual, memory, or reasoning failures due in the final analysis to the scene in question never having been properly attended to. Attentional failures are frequently encountered in the caselore on human error [see Companion Resource, especially Section 5], and are easy to experience for yourselves in "spot the gorilla" tasks - check it out now (on the Richard Wiseman website).
Attribute: The process of abstraction is at the heart of our ability to make representations of the world, but to do the process proper justice we must firstly consider the difference between a thing, and the "attributes" of that thing. Attributes are thus the properties, features, or parts of an object, and may be sub-categorised as perceptual, functional, relational, defining, characteristic, or irrelevant. Moreover, any permutation of these may have been the dimension(s) of commonality which prompted abstraction in the first place. However, not all attributes are given equal weight when describing an object - some seem to be relied upon more than others. In other words, attributes vary in their salience. Thus Grady (1977) found that in describing the person who had just sold them a New York subway token travellers always noted the sex of that person, but less regularly noted their race, age, hair colour, weight, and so on. Similarly, in flower design experiments Trabasso (1963) found that colour was far more value as the identifying attribute than was leaf angle, for example. Distinguishing between entities, attributes, and relationships is an important part of entity-relationship modelling.
Auditory Input Lexicon: Term popularised by Ellis and Young (1988) for the mental storehouse for whole heard word forms. [For further details see the longer entry under the same heading in our Psycholinguistics Glossary.]
Autobiographical Memory: Memory which is related to the self. When autobiographical memory relates to events in one's personal past, this will involve the appropriate episodic memory resources, and when it relates to the identities, meanings, and attributes of our own self and/or the things and other people around us, this will involve the appropriate semantic memory resources.
Bachman Diagram: "A graphic representation of the set relationships between owner and member record types used to analyse and document a database design" [source]. A less abstract representation of system data than that set down in the entity-relationship diagram, specifically one which contains physical implementation decisions particular to the DBMS available in the chosen system [see specimen]. Named after the technique's primary developer, Charles W. Bachman.
BADS: See Behavioural Assessment of the Dysexecutive Syndrome Test.
Behavioural Assessment of the Dysexecutive Syndrome Test (BADS): [See firstly executive function and dysexecutive syndrome.] The BADS test set [buy one from the publisher] assesses the all-points integrity of human executive function, and, as such, can either be included in a broader frontal battery or applied as it stands. The test package was developed by Wilson et al (1996), and requires (a) the subject to complete six separate practical tests, and (b) both subject and carer(s) to complete a 20-item diagnostic questionnaire (known as "the dysexecutive questionnaire", or DEX). The tests are as follows: (1) Temporal Judgement, (2) Rule Shifting, (3) Action Programme, (4) Key Search Task, (5) Zoo Map Task, and (6) Modified Six Elements Test.
Bender Visual Motor Gestalt Test: This test is grounded theoretically in the Gestalt laws of perception, and stimulus sets consist of simple line drawings designed to probe such early visual abilities as the law of continuity and resolving figure-ground. The test was devised by Bender (1938), and Anastasi (1990) mentions that it was initially "difficult to evaluate" (p487) because it was subjectively rather than objectively scored. Later versions are more precise.
Binding Site: Sites on the post-synaptic membrane where neurotransmitters act to induce either an EPSP or an IPSP.
Bloom's Six Levels of Knowledge: In the period 1949-1953, the American educationalist Benjamin Bloom chaired an influential "think tank" looking into the role of cognition in education. By a process of painstaking analysis, Bloom's team identified and ranked many different types of learning, memory, and thinking, setting them out finally in a complex six-level hierarchy of cognitive learning outcomes (Bloom, 1956). Bloom's hierarchy significantly influenced subsequent theory and research. Robert Gagné, for example, incorporated it into his discussions of learning outcomes (Gagné, 1975, p68), and Marton and Saljo (1976a,b) distinguished what they called "surface learning" (the recall of simple facts) from "deep learning" (the recall of issues and principles). Bloom's original six-level hierarchy is reproduced in Beard and Hartley (1984), and a five-level variant is found in Mulholland and Smyth (1988). The six-level version consists - in order of increasing difficulty - of knowing facts, understanding facts, applying facts (i.e. their use as knowledge, rather than their rote regurgitation), analysing that knowledge, synthesising that knowledge, and (finally and supremely) giving considered evaluations of that knowledge (Bloom, 1956, p18).
Brown-Peterson Technique: A memory experiment in which subjects listen to a list of items and then free recall as many as they can remember in any order either immediately or after a delay. In the delayed recall condition, an interpolated activity may be used. This is a distractor task inserted between the final stimulus item and the recall cue, and is intended to prevent rehearsal. By varying the nature, complexity, and confusibility of the distractor materials, the Brown-Peterson technique has often been used to investigate memory encoding procedures. The procedure is named after the researchers who first developed it, namely Brown (1958) and Peterson and Peterson (1959). For a specimen clinical application of this method, see Van der Linden, Coyette, and Seron (1992). [See now serial position effect.]
Bubble Lexicon: Term coined by Liu (2003/2003 online) to describe a lexico-semantic network structure capable of representing (as most such networks do not) nuance and context effects. [For a definition of context, and onward links on that topic, see this entry in our Psycholinguistics Glossary.]
"Calcium Switch": See protein kinase studies.
Capacitance: The ability of a structure - biological or otherwise - to hold an electrical charge.
Category: Two or more concepts having one or more attributes or relationships held in common, such that the commonality may itself become conceptualised and named. Thus the manifest physical and behavioural similarities between sparrows, eagles, and ducks would, by the process of abstraction, soon give rise to the category "bird". The detection of natural categories has considerable biological value because it makes for efficiency of cognition.
Category Test: [See firstly executive function and dysexecutive syndrome.] This test present patients with a short series of categorial exemplars (e.g., <duck, sparrow, pigeon .....>) and then marks them on their ability to respond with the appropriate category owner (i.e. "bird"). The category test is one of the Halstead-Reitan subscales.
Cation: A positively charged ion.
Cell Assembly: [See firstly synaptic learning.] The most influential early statement of the neuronal interconnection approach to memory was in Donald Hebb's book, "The Organisation of Behaviour", in which he described the interlinking of neurons as creating what he called a cell assembly, "a diffuse structure comprising cells in the cortex and diencephalon (and also, perhaps, in the basal ganglia of the cerebrum), capable of acting briefly as a closed system" (Hebb, 1949, xix). For Hebb, "any two cells or systems of cells that are repeatedly active at the same time will tend to become 'associated', so that activity in one facilitates activity in the other" (Ibid, p70). The idea of cells repeatedly assisting each other's firing is particularly well described in what has since come to be known as "Hebb's Rule". Artificial cell assemblies are known formally as neural networks and informally as Hebb-Marr networks, and the science of producing and using them is known as Connectionism. [For a broader introduction to this topic, see our e-paper on "Hebbian Theory".]
Cell Membrane: This is the outer surface of the cell, that is to say, the continuous layer which separates the cytoplasm within the cell from the interstitial fluid outside it. The membrane itself is a four-layered molecular structure, namely a bimolecular lipid layer "sandwiched" between two protein layers. Because it is selectively permeable to a variety of other molecules it largely controls the composition of the cytoplasm within - molecules which are wanted inside the cell are encouraged to pass inwards, and those which are wanted outside the cell are encouraged to pass outwards.
Central Executive: [See firstly Working Memory Theory.] Term coined by Baddeley and Hitch (1974) for the hypothetical cognitive structure which manages the routing of material between the slave systems and WMG, and which is accordingly the conductor of the mental orchestra, as it were. Baddeley later described the central executive as a "conceptual ragbag" (Baddeley, 1986, p224), because so many different higher functions could be attributed to it. This was not the fault of the central executive, however, but of a more general confusion as to what "higher functions" actually consists of, and some idea of the extent of the problem here can be gained by glancing at the six separate high-level aspects of supervisory processing identified at the top of Norman's (1990) diagram of the cognitive control hierarchy. Yet even to this day, no consensus functional decomposition of higher cognition has ever been carried out. The Daneman and Tardiff (1987) technique is an experimental paradigm for separately assessing the processing and storage elements of the central executive. Many modern memory theorists prefer to work with the alternative framework provided by the Norman-Shallice Model of Supervisory Attentional Function, in which the supervisory system acts as central executive.
CFST: See Weigl Colour-Form Sorting Task.
Cholinergic Transmission: Neurotransmission where the transmitter substance happens to be acetylcholine. [Compare adrenergic transmission.]
Cholinesterase: Enzyme responsible for the breakdown of acetylcholine during the recovery phase of synaptic transmission.
Chromosome: This is a thin filament of DNA double-helix found in the cell nucleus. It is vitally important to biological systems because it carries the body's genes. The nucleus of the human cell contains 46 chromosomes, each with a molecular weight of the order of 100 billion.
Chunking: A concept introduced by Miller (1956) to explain how more and more information might be handled without any increase in the brain's processing power. Thus, where previously unconnected items are learned together (such as putting individual numbers together in a novel way when learning a new telephone number), they gradually become chunked together and can thereafter be processed as a single item.
Cognition: "The acquisition, storage, retrieval, and use of knowledge" (Matlin, 1989).
Cognitive Estimates Test: [See firstly executive function and dysexecutive syndrome.] DETAIL TO FOLLOW
Cognitive Failures Questionnaire (CFQ): [See firstly executive function and dysexecutive syndrome.] DETAIL TO FOLLOW. Broadbent et al (1982).
Cognitive Framing: The application of anticipatory structures - "cognitive frames" - to the analysis of present perceptual input - see Minsky (1977). It is in the nature of cognitive frames that they facilitate perceptual decision-making by constraining it - specifically, as with any schema-based "top-down" process, they improve processing speed by investing in a little guesswork. Frames, in other words, are presumptions. Unfortunately, presumptions often prove to be unfounded and are then a possible cause of the sort of adverse incidents studied by forensic ergonomists. What happens when the active frame turns out to have been the wrong one (or is a perseveration of a proper one after it has ceased to be appropriate), is that it starts to prejudice accurate cognition rather than ensuring it. Such rogue frames force current input to fit an invalid presumption, and inappropriate behaviours get authorised as a result (and will persist, moreover, for as long as the error goes undetected). When this happens it leaves the cognitive system failing in its primary purpose - that of reality testing and maintaining situational awareness. The ability of a rogue frame to distort current sensory input so as to falsely validate its continued existence is often referred to as a "confirmation bias". [See also stereotype fixation and interrupt processing, and then compare with the phenomenon of impulsivity seen in cases of dysexecutive syndrome.]
Cognitive Map: A mental representation of the physical setting of the world.
Cognitive Overload: Perceptual, memory, or reasoning failures due in the final analysis to over-complexity of the perceptual scene given the cognitive resources available at that precise moment (which are themselves variable). Overload errors are (by definition) common in what Norman and Bobrow (1975) term "resource limited" processes - see Companion Resource.
Cognitive Psychology: By definition, the study of cognition, but, more critically, the study of the functional architecture of the brain as opposed to its structural architecture. Alternatively, the study of how the brain works at a level of analysis above the anatomical and physiological. The science of mind.
Concentration: How many things - in this case, ions - there are at a single point in three-dimensional space.
Concentration Difference: A difference in concentration between two points; a "slope" of concentration between these two points; a concentration gradient. Concentration gradients are important because ions tend to "flow down" the gradient until the concentration difference is cancelled out. This is what is happening whenever molecules/ions move through a permeable membrane, and it is due to random molecular movement.
Concentration Gradient: See concentration difference.
Concept: Concepts are abstractions from, and categorisations of, experience. They are "mental representations of objects, entities, or events, stored in memory" (Roth and Frisby, 1986, p19). Alternatively, a concept is "a mental representation of a category, which allows one to place stimuli in a category on the basis of some similarities between them" (Howard, 1987, p2). Alternatively, "concepts are the coinage of thought" (Johnson-Laird and Wason, 1977). The value of concepts is that they allow inferences to be drawn, namely that any new member of the category should possess the known typical attributes of the category as a whole. Concepts are vital to perception, action, memory, and communication. The term has a host of synonyms and near-synonyms, such as analog, prototype, and schema. [See also entity, object, and semantic memory, and contrast symbol.]
Confabulation: A clinical sign of an orienting deficit in neurological disease (and especially in dysexecutive syndrome). Attempting to make sense of a present situation not truly understood, and characterised (a) by inventing a plausible (but factually false) explanation, and (b) (as far as can be established) by believing that explanation to be true. Often termed "honest lying". It is also commonly observed that confabulations vary in their "plausibility", as follows: "Confabulations vary in plausibility from relatively mild - for example, filling in of gaps, loose paraphrasing and temporal displacements of actual events - to more severe, highly implausible and bizarre accounts. Some confabulations have qualities similar to those of real memories." (Johnson and Raye, 1998, p141).
Confusibility Studies: A confusibility effect is a memory deficit which emerges when the stimuli to be retained are similar in a certain respect. This is because the corresponding engrams are presumed to be confusible in that same respect, and therefore tend to get irretrievably overlain. However, this only happens if the attribute variable in question is being actively used for the encoding of the material in question. Tests of confusibility are therefore tests of encoding, and, using them, two major confusibility effects have been identified, namely the phonological similarity effect and the semantic similarity effect.
Connectionism: The doctrine that cognition can be modelled (and therefore better understood) by connecting up artificial neurons, either in fact, or in simulation on a computer. [For further details, see our e-paper on "Connectionism"]
Connectionist: Follower of Connectionism as a philosophical school and set of explanatory principles.
Consolidation: Term coined by Muller and Pilzecker (1900) to describe the process by which short-term memories became physically permanent as structural engrams. However, the term is also commonly used to describe the transition between STM and LTM as psychological phenomena. Thus, we may describe our experiences as consolidating into knowledge at the psychological level, or we may describe our neural spiking as consolidating into enlarged synapses at the physiological level, but ultimately we are probably referring to one and the same thing - all we have to do is find a way to cross the explanatory gap between the two levels of explanation.
Contamination: See Co-Witness Contamination.
Content Addressable Filestore: Computing terminology for the calculation of a physical storage address, by algorithm, from a predetermined field within the record to be stored.
Contention Scheduling: Term borrowed by the Norman-Shallice Model of Supervisory Attentional Function from virtual machine operating systems in computing [as described in some detail in our e-paper on "Short-Term Memory Subtypes in Computing and Artificial Intelligence", Part 5 (Section 1.2)], where it is describes the ability of said operating systems to prevent different programs clashing for a common resource.
Context Rehearsal: [See firstly pragmatics and rehearsal.] Term coined by Parker-Rhodes (1978) to describe the refreshing of the high-level conceptual (i.e. pre-linguistic) codes during sentence production, using feedback from, and presumably some sort of re-perception of, the sentence(s) being produced. Hence a form of high-level output monitoring along the lines of the "thought loop" proposed by Lee (1951) [and described in greater detail in our e-paper on "Speech Errors, Speech Production Models, and Speech Pathology" (Section 5.1)].
Contiguity: Literally, closeness to, or adjacency. The term needs to be applied in two ways in psychology, firstly contiguity in space (i.e. physical proximity) and secondly contiguity in time (i.e. simultaneity, or nearly so), both of which seem to be able to promote the association of the things contiguous. Contiguity effects are commonly cited as one of the basic principles of learning and memory.
Corsi Blocks Test: This is a test of sequential memory involving nine blocks irregularly laid out on a base board. The investigator points to a number of blocks in turn at a rate of one per second, and the patient then has to repeat the sequence in the same order. The test sequences then get longer and longer until the patient starts to make errors.
Co-Witness Contamination: This is the technical term for the corruption of one person's eye-witness memory by exposure to the accounts of other eye-witnesses [see Steve Lindsay on this].
Cytoplasm: This is the fluid medium of the non-nuclear part of the cell. It is 90% water, with a variety of other substances - salts, sugars, dissolved blood gases, and proteins - in colloidal (gel-like) solution. The main difference between the cytoplasm and the interstitial fluid is that the cytoplasm contains far more potassium and phosphate ions. [Compare nucleoplasm.]
Cytoskeleton: This is a microscopic framework of intracellular protein filaments spreading like scaffolding throughout the cytoplasm and giving it additional rigidity.
Dale's Law: The principle that while there are many different neurotransmitters to choose from, each individual neuron relies on only one (implying, of course, that all synapses from a given neuron use the same neurotransmitter).
Daneman and Carpenter (1983) Sentence Span Technique: This technique involves presenting subjects with sequences of two to six sentences, each of 13 to 16 words. Subjects have to read the sentences out loud, and attempt to remember the last word of each. They are then asked to recall as many last words as possible (in any order). The sentence span is the mean number of sentences which can be coped with at 60% accuracy or better. [For a specimen clinical application of this method, see Van der Linden, Coyette, and Seron (1992).]
Daneman and Tardiff (1987) Technique: This technique was developed to assess the processing and storage aspects of the central executive separately. In this paradigm, four words are presented which can be combined to make longer words. Thus (for example) MUSE, AU, VENT, and BERGE, can be combined to make MUSEAU, AUVENT, and AUBERGE. These combinations can be at, or not at, one of the syllable boundaries of the derived word. The task is for the patient to find the new word which does not contain one of these syllable boundaries, and the necessary trials are carried out with or without a memory load (i.e. the patient does not always have to recall the individual words as well use them to select one of the target derived word.) The number of correct selections is therefore held to be a measure of processing, while the number of correct recalls is a measure of memory. [For a specimen clinical application of this method, see Van der Linden, Coyette, and Seron (1992).]
Decay: This is the doctrine (originally from Ebbinghaus, 1885) that forgetting can be caused by the gradual disappearance of a memory trace over time. That is to say, you forget because your engrams spontaneously become fainter and fainter over time, unless you revisit them occasionally to refresh them. [Compare interference.]
Declarative Memory: Same as propositional memory.
Decremental Propagation: Small local changes in potential across the cell membrane are easy to induce both electrically and chemically, but if they do not reach the action potential threshold, will simply die away like ripples in a pond. No action potential develops. Until they die away, however, there is a potential gradient spreading outwards from the point of stimulation by "decremental" - that is to say, ever decreasing - propagation.
Deep Learning: [See firstly Bloom's six levels of knowledge.] Term coined by Marton and Saljo (1976a,b) to characterise the learning of issues and principles. [Contrast surface learning.]
DEX: See Behavioural Assessment of the Dysexecutive Syndrome Test.
Duplex Model of Memory: [See firstly consolidation.] Any "two-box" model of memory which separates STM and LTM. Duplex models were rendered largely obsolete by the discovery of sensory memory in 1960.
Dysexecutive Questionnaire: See Behavioural Assessment of the Dysexecutive Syndrome Test.
Dysexecutive Syndrome: [See firstly Working Memory Theory.] Term coined by Baddeley (1986, p238) as a synonym for frontal lobe syndrome, and nowadays perhaps the preferred term. The concept was introduced in a chapter entitled "The Central Executive and its Malfunctions", in which the 1970s working memory concepts were compared with the (then still new) Normal-Shallice Model of Supervisory Attentional Function, and in which Baddeley graciously admitted that Norman and Shallice had succeeded in integrating memory and attentional phenomena, a task he personally had been "evading". [See now confabulation, impulsivity, mental rigidity, and utilisation behaviour.]
Echoic Memory: An auditory version of iconic memory.
Ecphory: [From the Greek ekphorein = to make known; reveal.] A valuable, but oft-ignored, term devised by Tulving (1972) to describe a largely pre-conscious process in which retrieval cues are brought into contact with stored information, causing parts of that stored information to be reactivated, and thus remembered. This would be rather like shining a flashlight around a darkened room: the cues are what guides your hand in a particular direction, and the information retrieved is whatever is momentarily lit up by the beam - what you see at any one instant may not be what you are looking for, but may well tell you in which direction to look next. The process must presumably work in close association with the mind's memory indexing mechanisms.
Eidetic Imagery: A particularly vivid form of visual imagery, more fully described in Haber (1969).
Electrostatic Force: [See firstly resting potential and equilibrium.] The charged particles which move back and forth across the cell membrane in excitable tissues are capable of exerting relatively strong intermolecular forces. Like charges (both positive or both negative) repel, and unlike charges (i.e. one of each) attract. This serves to prevent too many like-charged particles accumulating in the same place, and this, in turn, creates a limiting back-pressure should you happen to be metabolically pumping like-charged ions into that place for some purpose.
Electrotonic: In general, a stable, rather than constantly changing (clonic) electrical potential. In the present context, the neuron's resting potential is an electrotonic potential.
E-MOP: See episodic memory organisation packet.
Encoding: Encoding is what the nervous system does to the stimuli which impinge upon it. It is the mechanism by which the various attributes of the external stimulus are converted to an internal - that is to say, neural - signal. With a visual stimulus, for example, you need to encode size, shape, colour, brightness, and movement for each of 125 million retinal rods and cones, and to do the necessary encoding you only have 1.25 million optic nerve fibres to play with [a 100:1 reduction factor!], and all you can do with these nerve fibres is determine which ones should fire, at what rate, and for how long. Paivio (1986) provides a useful theoretical overview of the encoding process, and ventures to name the three basic operations involved. Firstly, there is representational encoding, which is encoding by external attribute (thus an iconic image would be a representational encoding of a visual stimulus, and an echoic image would be a representational encoding of an auditory stimulus). Secondly, there is referential encoding, which involves producing "referentially related verbal and nonverbal memory trace components". This creates a dual trace, the two aspects of which are (a) the thing in question [the concept], and (b) its name [the symbol]. And thirdly, there is associative encoding, which involves creating links, or associations, between a given new memory and as many pre-existing ones as possible. The more numerous the links, the harder the new memory is to forget. Encoding is thus one of psychology's major persistent issues (the nature of mental representation) under another name, and understanding it is one of the keys to understanding the mind as a whole, let alone memory in isolation! [See now transcoding. For a detailed example of progressive encoding and recoding/transcoding within the longitudinal cognitive system, see the flowline annotations in Ellis (1982), and for quantification of the reduction in information loadings which transcoding permits, see Frank (1963).]
Endoplasm: Same as cytoplasm.
Endoplasmic Reticulum: This is a complex network of intracellular microtubules and cisterns (small chambers) which permeates the cytoplasm. Its walls - the reticular membrane - share the four-layered molecular structure of the cell membrane. Indeed, at some points on the cell membrane there are pores where selected endoplasmic tubules pass through the cell membrane to communicate with the interstitial fluid. At other points it is continuous with the Golgi apparatus. In some regions the reticular membrane is heavily studded with ribosomes, giving it a granular appearance.
Engram: It has long been suspected/agreed that the process of retaining information over time requires some sort of structural change within the nervous system, but opinions as to the nature of this trace continue to differ. However, its name at least is fairly well established: it is usually referred to as the "memory trace", or engram (literally, "that which has been engraved"). The term engram derives from Richard Semon (1904), who defined it as "a permanent change wrought by a stimulus on any living substance". Experience, in other words, must somehow make its mark upon the brain, and the engram is that mark.
Entity: "..... a person, object, place or event for which data is collected. For example, if you consider the information system for a business, entities would include not only customers, but the customer's address, and orders as well" [source]. Alternatively, entities are "the elements or parts of a system" (Kramer and de Smit, 1977:14), especially objects and things. Entities are "to a significant degree discontinuous with the environment that contains them" (Salthe, 1985:23), their individual qualities are known as attributes, and they influence each other through relationships.[See now Entity-Relationship Modelling.]
Entity-Relationship Diagram: See entity-relationship modelling.
Entity-Relationship Modelling (ERM): [See firstly entity, relationship, and attribute.] ERM is of the basic skills of modern systems analysis. It is a method of modelling which requires the identification and naming (a) of all the entities dealt with or touched upon by an information processing system, (b) of the attributes of said entities, and (c) of the relationships between them. The result of the analysis is usually expressed diagrammatically in an Entity-Relation Diagram (ERD), and this subsequently serves as the master "data model" for the system in question. The ERD reflects shows the "natural logic" within your data, identifying all the things which matter (the entities) and how they relate to each other (the relationships).
Ependymins: [See firstly calcium switching.]
If calcium-switched post-synaptic sensitisation has a lifetime measured in
hours, then it cannot explain memory for longer periods. Membrane
sensitisation, in other words, is NOT the sort of structural change long
believed to be involved in the formation of LTM engrams, and so we still need a
mechanism capable of consolidating memory into a structural form. A
typical worker in this latter area is Victor Shashoua
Episodic Memory: The concept of episodic memory derives from a 1972 paper by Endel Tulving, who argued that the material used in memory experiments was far from "natural" (Tulving, 1972). In particular, it did not tap the ability of subjects to record their personal life events in the form of an internal autobiography. Tulving therefore proposed distinguishing episodic memory - the memory for occurrence or episode, from semantic memory - the memory of meaning. Episodic memory is thus LTM for past events - a sort of mental life history on video [e.g., the ability to recall what you had for breakfast this morning]. Episodic memory is basically a time-sequenced accumulation of past perceptual scene analyses, and in the very long term it tends to be the emotional events which get remembered best [e.g., first kisses, stressful examinations and interviews, insults, anger, indebtedness, etc.]. The name "flashbulb memory" [definition] is sometimes given to events such as assassinations and disasters, where the emotion is so intense that it freezes the imagery in time [which is why those who are old enough can remember what they were doing when they heard of President Kennedy's assassination (younger readers will in due course experience much the same phenomenon with the September 11th attacks)]. [See now episodic vs semantic memory, event memory, imagery, and Script Theory.]
Episodic Memory Organisation Packet (E-MOP): [See firstly the entry in the LayNetworks e-glossary.] The episodic memory access mechanisms proposed here help provide the indexing necessary to achieve effective random access to the body of LTM.
Episodic vs Semantic Memory: [See firstly episodic memory.] Tulving gave many examples to illustrate the difference between episodic memory and semantic memory. Episodic memories would include the fact that ten years ago one moved house, or that last Saturday one went to a wedding, or that one passed one 's driving test in 1991. Semantic memories would include one 's ability to know that water boils at 100o centigrade, that "to wane" means "to get smaller", and that penguins are birds (but possibly also books or chocolate bars). More recently, Tulving (1987) has described episodic memory as the "highest memory system" (p72) because it gives people their uniqueness - their memories of their personal past lives. Semantic memory, by contrast, is remarkably constant from person to person, and does not need to relate to specific objects and events in order to be used (nor, in most cases, can you even remember where or when you learned something). Thus, whilst we may well have all done different things yesterday, we would, if asked to define the word "chair", generate more or less the same definition. In other words, episodic memory is personalised and unique, but semantic memory is far more encyclopaedic.
Epistemology: "The study of theories of knowledge or ways of knowing, particularly in the context of the limits or validity of the various ways of knowing" [source]. The science and philosophy of semantic memory.
EPSP: See excitatory post-synaptic potential.
Equilibrium: The ion concentration at a given point on the neural cell membrane at which the three competing molecular transport forces (random molecular movement, metabolic pumping, and electrostatic forces) balance out. This results in a resting potential of -70mV.
Another view of the episodic vs semantic memory distinction comes from
Roger Schank of Northwestern
University. Schank is a leading AI researcher who has
been forced to postulate different subtypes of episodic memory in order
to make progress with cognitive modelling on computers. To start with, he
distinguishes between specific event memories (EMs), which he describes
as "specific remembrances of particular situations" (Schank, 1982, p230), and generalised event memories
(GEMs), which are abstractions from many
Excitatory Post-Synaptic Potential (EPSP): [See firstly post-synaptic potential.] A local 3-4mV depolarisation of the post-synaptic neural membrane, following the arrival of an action potential at the pre-synaptic side of the synaptic cleft, provided only that the neurotransmitter involved is excitatory. This depolarising event is important, because it moves the receiving neuron closer to its action potential threshold, thus making it more likely to fire. [Contrast inhibitory post-synaptic potential.]
Executive Function: [See firstly frontal lobe syndrome.] That which occupies the processor(s) at the top of the motor hierarchy, and therefore the faculty (or cluster of faculties) which is failing in dysexecutive syndrome. In fact, four major components of executive functioning may be identified, namely (a) orienting towards and attending properly to the things which really matter in one's surroundings, (b) inhibiting impulsivity of response, in favour of (c) appropriate forward planning, (d) executing - and meaningfully monitoring the execution of - the resulting plans. [See now frontal battery.]
Exocytosis: The releasing of neurotransmitter chemicals into the synaptic cleft by passing "bubbles" of them - synaptic vesicles - out through the pre-synaptic cell membrane.
Experiential Learning: Term devised by Kolb (1983) to refer to conceptual knowledge acquired over time from simple performance, and generally applied specifically within educational theory rather than within mainstream memory theory. The principle of experiential learning is that conceptual knowledge [ie. semantic memory] should not be taught explicitly, because that approach verges on rote learning, and is largely ineffective. Instead, it needs to be based on natural or contrived learning experiences. These experiences create a corpus of episodic memory, event memory, and procedural memory, which, over time, by processes of abstraction and reflection, create true understanding. Much of the critical acclaim for Kolb's approach derives from the fact that it integrates the various types of knowledge exceptionally well. Kolb's disciples Dennison and Kirk (1990) use the motto "Do - Review - Learn - Apply" to summarise the substages of the overall process.
Eye-Witness Memory: Those elements of human memory ability involved when someone witnesses an event which either at the time or later turns out to have a legal aspect to it.
Eye-Witness Memory Theory: Those elements of human memory theory which need to be taken into account when forensic psychologists are called upon to testify as to the reliability of individual eye-witness testimony. [see the separate entries for
Frontal Battery: [See firstly frontal lobe syndrome and dysexecutive syndrome.] A loose collection of psychometric tests - both adhoc and formally standardised - applied over a period of time to build up a bigger picture of a frontal patient's executive function. To do the frontal assessment properly, therefore requires tests of each executive processing component (attention, planning, execution, etc.). Here are some typical tests, and the components they are supposed to be assessing. [For a specimen clinical application of this method, see Van der Linden, Coyette, and Seron (1992).]
Explanatory Gap: The practical problem faced by followers of Reductionism in relating micro observations to macro observations. To take a memory phenomenon as a convenient example, we know what ependymins are and how they behave, and we can readily demonstrate memory consolidation at a psychological level. However, it is much harder to prove any causal relationship between the two - that ependymins help create engrams - because there is as yet no mapping between the chemistry and the psychology.
Extracellular Fluid (ECF): This is the generic term for all non-cellular bodily fluids. There are three main types of ECF, two of which, lymph and blood, are confined into circulatory systems and do not concern us here. The third type, the interstitial fluid is not circulated as such, but simply fills in all the gaps between the other components of the body.
FDPX [Project Konrad]: A functionally delimited processing module [as opposed to an anatomically delimited one]. Konrad recognises 21 different FDPXs, but only currently simulates the uppermost 11 of them [see the processing hierarchy]. Each FDPX contains many content-addressable LTM records.
First Messenger Neurotransmission: See second messenger neurotransmission.
Flashbulb Memory: See episodic memory and imagery.
Free Recall: The recall of stimulus items in any order (as, for example, in the Brown-Peterson technique). (Those interested in studying free recall will find some useful standardised data on 925 English nouns in Rubin and Friendly, 1986.)
Frontal Amnesia: See frontal lobe syndrome.
Frontal Lobe Syndrome: "The intriguing but puzzling pattern of deficits sometimes associated with damage to the frontal lobes" (Baddeley, 1986, p236). One of the earliest accounts of the effects of a frontal lobe lesion is Bigelow's (1850) [timeline] account of the brain-injured American railway labourer Phineas Gage. This was followed by investigations of deliberately inflicted frontal lesions in animals by the likes of Ferrier (1886) [timeline] and Bianchi (1895, 1922). Bianchi (1922) summarises the animal studies as showing five areas of frontal deficit, namely (a) loss of "perceptive power", leading to defective attention and object recognition, (b) reduction in memory, (c) reduction in "associative power", leading to lack of coordination of the individual steps leading towards a given goal, and thus to severe difficulty solving anything but the most simple problems, (d) altered emotional attachments, leading to serious changes in "sociality", and (e) disruption of focal consciousness and purposive behaviour, leading to apathy and/or distractibility. Similarly, Denny-Brown (1951) surveyed frontal lobe problems in humans, and found much the same pattern of deficit, concluding, therefore, that memory defects were common enough following frontal damage, but were far from being the primary characteristic. Frontal amnesias, in other words, are not as immediately obvious as those arising from temporal lobe damage. Nor do many memory tests readily detect frontal lobe damage, for which reason clinical neuropsychologists have devised special frontal lobe tasks, or frontal batteries, to be selectively sensitive to frontal lobe damage.
Functional Architecture: The arrangement and organisation of process as opposed to structure.
Functional Decomposition: Another of the basic skills of modern systems analysis [alongside entity-relationship modelling]. The recursive analysis of the sub-processes within a process, beginning ideally at the very top, and continuing down the hierarchy of processes until one of two things happens - either (a) you reach the level at which you have seen enough, or (b) you reach a level beyond which no further decomposition is possible (the processes at this level being known as functional primitives). [For practical guidance with this technique, see our e-tutorial on "How to Draw Cognitive Diagrams" (Section 3).]
Functional Primitive: See functional decomposition.
Gene: This is a subsection of a chromosome. It contains just enough genetic material to manufacture a single molecule of protein (although it can do this many times). Each human chromosome contains of the order of 100,000 genes, each of which has a molecular weight of the order of 1 million and contains perhaps 1500 nucleotide pairs.
Generalised Event Memory (GEM): See event memory.
key points in a story. [See now
G-Protein: See protein kinase studies and second messenger neurotransmission.
Golgi Apparatus: This is an extension of the endoplasmic reticulum, seemingly responsible for directing newly formed proteins back into the cytoplasm. It does this by forming them into small vesicles known as secretory granules which can then be passed in through the reticular membrane by a process known as endocytosis. The lysosomes are a type of secretory granule.
Graded Potential: [See firstly potential difference and propagation.] Small changes in membrane potential which die away by decremental propagation, that is to say, smoothly with time or distance and without inducing an action potential.
"Hebb-Marr Network": Same as neural network. [For a broader introduction to this topic, see our e-paper on "Connectionism".]
"Hebb's Rule": [See firstly cell assembly.] The law of contiguity applied to synaptic learning. Originally stated as follows: "Let us assume then that the persistence or repetition of a reverberatory activity (or 'trace') tends to induce lasting cellular changes that add to its stability. The assumption can be precisely stated as follows: When an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A's efficiency, as one of the cells firing B, is increased." (Hebb, 1949, p62; italics original.)
Higher (Mental) Functions: A term initially devised by neurologists to encompass all cognitive functions over and above those concerned with reflex, perceptual, and motor behaviour. Broadly speaking, the same set of processes now treated as executive function.
Iconic Memory: Very short-term visual memory, first formally investigated by Sperling (1960).
<< AUTHOR'S NOTE: The distinction between very short-term memory and ordinary short-term memory is unlikely to be a physiological one. Both forms are probably "electrical STM" as defined in the Introduction to this paper, albeit probably located in different processing modules, one more peripheral than the other. >>
Imagery: The non-conceptual memory of past visual and/or auditory scenes. Presumably, therefore, some sort of partly reactivated perceptual memory, with associations to both episodic memory (for the context within which the scene was originally experienced) and propositional memory (for the interpretation placed upon it at the time). The ability to re-live a serious car accident in one's mind, for example, would depend on a central flashbulb memory of the moment of impact, say, supported by a broader episodic memory of the reasons for the journey, say, and a few summative propositions describing what you know conceptually and factually about the incident, for instance, who was driving at the time and who was killed or injured. It is commonly proposed that thinking in images is a major component of creative thought, and that making good use of "visuo-spatial" LTM is therefore one of the major "right hemisphere" skills. The most vivid form of visual imagery is known as eidetic imagery.
Impulsivity: A clinical sign of a response-inhibiting deficit in neurological disease (and especially in dysexecutive syndrome). Responding with the first thing which comes into your head, despite knowing this to be an inappropriate strategy.
Indexing: [See firstly event memory and story memory.] The concept of "indexing" is a valuable, but oft-ignored, aspect of Schank and Abelson's (1995) story-based approach to memory, and it earns its value from the simple fact that a prior experience is only useful if it can be used. That means being able to get at relevant experience when you need it; and quickly, too. Event and story memories must therefore be flexibly retrievable by a biological equivalent of the sort of random access mechanisms used in computing, and indexes are the mechanism of that flexibility. To be effective, memory "must contain both specific instances (memories) and labels (indexes) used to trace memories of experiences. The more information we are given about a situation, the more places we can attach it in our memory, and the more ways it can be compared to other cases in our memory" (p7). The index entry points "may be locations, attitudes, beliefs, quandaries, decisions, conclusions, or whatever [and] the more indexes we have, the greater the number of comparisons we can make to prior experiences, and hence the greater our learning" (p7). [See now ecphory.]
<< AUTHOR'S NOTE: Indexing is thus the biological counterpart of the various forms of random access OBTAIN built into network database software, and introduced more fully in our e-paper on "Database Navigation and the IDMS Semantic Net". >>
Inhibitory Post-Synaptic Potential (IPSP): [See firstly post-synaptic potential.] A local 3-4mV hyperpolarisation of the post-synaptic neural membrane, following the arrival of an action potential at the pre-synaptic side of the synaptic cleft, provided only that the neurotransmitter involved is inhibitory. This hyperpolarising event is important, because it moves the receiving neuron further from its action potential threshold, thus making it less likely to fire. [Contrast excitatory post-synaptic potential.]
Inner Speech: Thinking by talking silently to oneself. One of the most important (and mysterious) cognitive abilities, and typically modelled as a feedback loop, as, for example, Route #11 (northbound) on the Ellis and Young (1988) transcoding model.
Interference: This is the doctrine (originally from Ebbinghaus, 1885) that forgetting can be caused by competing demand for memory resources, rather than by simple time lapse alone. You forget, in other words, because one engram can become mixed up with, and eventually indistinguishable from, earlier or later ones. Where this interference is from more recent material, it is termed retroactive interference, and where it is from pre-existing (i.e. older) material, it is termed proactive interference. [Compare decay.]
Interpolated Activity: See Brown-Peterson technique.
Interstitial Fluid: A type of extracellular fluid. It is mainly composed of water, with traces of other substances - salts (predominantly sodium chloride), sugars, dissolved blood gases, and proteins - in solution. The main difference between interstitial fluid and the cytoplasm is that the interstitial fluid contains far more sodium and chlorine ions. [Compare nucleoplasm.]
Ion: An atom with one or more electrons in surplus or deficit. Because each electron carries a unit negative charge, if there is a surplus of them the overall atomic charge is a net negative (making the ion in question an anion), and if there is a deficit of them the overall atomic charge is a net positive (making the ion in question a cation). [See now electrostatic force.]
IPSP: See inhibitory post-synaptic potential.
Knowledge: Loosely speaking, the sum total of the representations of the world contained in the mind, on all subjects (including our own selves) and involving all memory types. But avoid specific use of this term in technical arguments in favour of the more precise propositional knowledge (or as appropriate).
Label: See indexing.
Logic (of a Process): The sequence of events by which a problem can be solved. These events can be, for example, movements of, manipulations of, or tests of, memory content.
Long-Term Working Memory (LTWM): [See firstly working memory.] Ericsson and Kintsch (1995) [useful commentary and extracts] have recently introduced the concept of long-term WM (an assertion which would once have been considered a contradiction in terms) to account for tagging phenomena in complex cognitive behaviours like the comprehension of text. What Ericsson and Kintsch noted was that such highly complex tasks typically require access to large amounts of what is known as "domain specific" - ie. logically themed - knowledge. You might see this, for example, in having the rules fresh in your mind while playing a game of chess, or your knowledge of memory theory fresh in your mind while reading this paragraph. Ericsson and Kintsch therefore proposed the need for matching domain-specific "retrieval structures" capable of rapidly and flexibly retrieving information from LTM, and in some way of pre-organising it to the demands of the problem. These retrieval structures are then the mechanism by which ongoing thought can turn to a particular domain of knowledge and immediately be served up with a "control panel" of sorts, by which the LTM within that domain is best handled. The fact that these retrieval structures were undeniably LTM structures themselves, but could interface flexibly with ongoing cognition, led to them being termed LTWM. For our own part, we see LTWM as demanding precisely the sort of "touch-and-glow" electrochemical medium-term memory promised by second messenger neurotransmission.
Lysosome: This is a small spherical organelle containing digestive enzymes. Lysosomes help "sweep up" foreign substances entering the cell.
Managerial Knowledge Units: [See firstly frontal lobe syndrome, planning, and script execution.] Term coined by Grafman (1989) for cognitive structures in the frontal lobes which coordinate lesser blocks of memory into meaningful sequences [1994 press release]. More or less synonymous, therefore, with the terms action schema and script. Recently described as a category of script-like structures "with a beginning and an end and a hierarchical organisation going from more abstract [.....] to more concrete levels" (Chevignard et al, 2000/2003 online), and highly susceptible to frontal lobe lesions.
Gist: [See firstly gist and
Memory Span: A memory test in which subjects are presented with strings of test items for short term rehearsal. Performance levels off in normals as soon as the string exceeds about seven items in length, and is one of the first abilities to fail following neurological trauma.
Memory Trace: Same as engram (to be preferred).
Metabolic Pumping: [See firstly random molecular movement.] Our bodies are made up of billions of cells, each one surrounded by a porous cell membrane. The passing of chemicals across these membranes due to osmosis is a significant biological problem because if steps were not taken to prevent it, the cytoplasm within the cell would either gain fluid from its surroundings (thereby becoming diluted, even to the point of splitting the cell membrane open), or else lose fluid to its surroundings (thereby becoming thickened and unable to carry out its normal metabolic tasks). Now evolution seems to have solved the problem of porous membranes in a number of ways. For example, one method was to keep the concentration of the cytoplasm and its surrounding fluids equal. Another was to use thicker membranes, such as when Schwann cells provide a myelin sheath to the axons of myelinated neurons. However, the most sophisticated method of all was to develop pores in the cell wall capable of chemically forcing the unwanted particles back out again as they invaded (or the wanted ones back in again as they escaped). This process consumes energy, however, for which reason it is known as metabolic pumping. A metabolic pump is thus a device within the cell membrane which picks up particles from one side of the membrane and actively transports them to the other. Provided it is pumping in the right direction, it can be used to counteract the effects of osmosis. It is conventional to specify the particle concerned when the pump is named. The neuron's sodium pump, for example, pushes sodium ions outwards so as to counteract the natural inflow due to random molecular movement. Dean (1941) has been credited with having first suggested active metabolic pumping of sodium ions in this way.
Repeated Production: A memory test in which subjects are presented with
test stimuli and required to reproduce them from memory after a series of
intervals. Wulf (1922) used this method to
investigate progressive changes in the memory trace for simple visual shapes,
Method of Savings: This is a powerful but complex memory measure dating back to Ebbinghaus (1885). The subject is firstly trained to criterion on the learning task in question. Learning is then discontinued for a period, as a result of which some forgetting will take place. At the end of this period, the subject is retrained to the original criterion. The number of retraining trials, however, is less than it would have been had there been no initial training (because some learning survived the delay period). Retraining measures (or "relearning" measures, or "savings") can thus be used to measure both the amount of initial learning and the speed of its loss.
Serial Reproduction: A memory test in which subjects are presented with
test stimuli and required to reproduce them from memory after an interval. This
reproduction is then used as the test stimulus for a second subject, whose
output is used as the stimulus for the third subject, and so on.
Minimum Stimulus Current: The smallest continuous stimulation required to exceed the action potential threshold.
Misinformation: The vulnerability of eye-witnesses to the accidental or deliberate planting of incorrect facts into recalled testimony, which tend to be conflated with genuine recall.
Mitochondrion: (Pl: Mitochondria.) This is a sausage-shaped organelle of which several hundred may be present in a given cell. It acts as the cell's "powerhouse", that is to say, it is where the energy source adenosine triphosphate (ATP) is stored pending demand.
MMSE: See Mini Mental State Examination.
Mnemonic: An encoding strategy for enhancing memory performance.
Modal Model of Memory (MMM): A consensus (hence "modal") approach to memory theory which emerged during the 1960s, and which was most clearly expounded by Atkinson and Shiffrin (1971). The MMM treats memory phenomena as beginning with sensory memory, advancing to STM, and consolidating to LTM, and as being supported along the way by such processes as rehearsal and encoding. The approach eventually lost popularity in the mid-1970s, due to competition from Working Memory Theory.
Sorting Test (MCST): See
Motor Hierarchy: See dedicated support article.
MTEV [Project Konrad]: An event giving rise to activity within the brain of a duration beyond that of momentary electrical excitation but not resulting in permanent structural change.
Multiple Errands Tests: [See firstly executive function and dysexecutive syndrome.] The Multiple Errands Test is a simple test of the integrity of the planning-execution components of human executive function, and, as such, is commonly included as a frontal battery test. The test was developed by Shallice and Burgess (1991), and involves taking the patient to a convenient shopping mall, having previously briefed him/her with eight tasks. Six of the tasks are shopping list tasks such as "buy a brown loaf", and the seventh is to be back at a nominated rendezvous point after 15 minutes. The eighth task is to obtain and write down four complex facts [such as the name of the shop most likely to sell the most expensive item, or a particular bank exchange rate]., and requires the subject to [Compare Six Elements Test.]
Neural Network: [See firstly Connectionism.] A non-biological simulation of a biological cell assembly, either (a) simulated "in hardware" using purpose-built electronic circuitry, or (b) simulated "in software". [For further details, see our e-paper on "Connectionism".] CAUTION: Do not get neural networks confused with neuronal networks, which are made out of real neurons. EXCEPTION: Damasio (2002, p50) uses the term "neural network" as a synonym for cell assembly.
Neuron, Non-Spiking: Type of neuron whose normal mode of operation involves transmitting graded potentials only (rather than action potentials) during decremental propagation.
Neuronal Network: A network of neurons. Same thing as cell assembly. NOT A NEURAL NETWORK!!
Neuroplasm: A neuron's cytoplasm.
Neurotransmission: Reduced to basics, there are actually three ways for chemicals to leave a given cell, namely (a) by simple diffusion through the cell membrane, (b) by passing out through pores in the cell membrane such as the sodium ion channel (possibly - but not necessarily - helped on their way by metabolic pumping), or (c) by exocytosis, the releasing of synaptic vesicles of concentrated agent. The major mechanism as far as the synapse is concerned is exocytosis, where the agent in question is the neurotransmitter substance, and the point of exit is the pre-synaptic side of the synaptic cleft. The vesicles themselves are originally formed by "budding off" the Golgi apparatus as soon as sufficient new agent has been synthesised. They then migrate cell-internally though the cytoplasm to the synaptic button. Once there, they are sensitive to calcium ion concentration changes. Specifically, as an action potential arrives at the synaptic button it depolarises the cell membrane. This opens voltage-gated calcium channels and allows calcium ions from the interstitial fluid to flood into the cytoplasm, forming - as Levitan and Kaczmarek (1991) colourfully describe them - miniature "volcanos of calcium" (p159) on the inner surface of the cell membrane. This sudden arrival of calcium ions somehow renders the vesicle membrane more compatible with the cell membrane, and this causes both membranes suddenly to coalesce [as when a champagne bubble ceases to exist upon reaching the surface], thus spilling the vesicle's contents out into the synaptic cleft, where the molecules (not the vesicles any more) now migrate cell-externally to the adjacent cell. As for what happens within the post-synaptic neuron, the key concepts are those of binding and receptor sites. Phrased simply, the neurotransmitter molecules now bind with (that is to say, fit onto) suitably shaped molecules in the surface of that membrane. These receiving molecules are known as receptors.
Neurotransmitter: [See firstly neurotransmission.] The contents of the synaptic vesicles released from the pre-synaptic neuron into the synaptic cleft. These chemicals induce a post-synaptic potential in the receiving neuron.
Node of Ranvier: The space between adjacent Schwann cell sheaths on a myelinated axon. The only points on such an axon where an action potential can occur. [See now saltatory conduction.]
Non-Decremental Propagation: Propagation whereby an action potential at one point on a cell membrane induces a full action potential either (a) at an immediately adjacent point in the neural membrane, or (b) some way off at the next node of Ranvier. Because each action potential consumes metabolic energy, its power does not decrement (= decrease) with distance. [Compare decremental propagation.]
Norman-Shallice Model of Supervisory Attentional Function: A more powerful development of Norman and Bobrow's (1975) Resource Allocation Theory. The Norman-Shallice model is a three-layer/five-box control hierarchy (similar to Craik, 1945) sculpted on top of a sixth box containing a schema selection process. This latter process is characterised as relying as much on inhibitory mechanisms as upon excitatory, so that the momentary salience of one motor program comes in large part from a carefully contention-scheduled lack of competition from all the others (Shallice, 1982, p200). Shallice (1988) summarises the role of the supervisory system as follows: "..... the Supervisory System [has] access to a representation of the environment and of the organism's intentions and cognitive capacities. It is held to operate not by directly controlling behaviour, but by modulating the lower level [resources] by activating or inhibiting particular schemata. It would be involved in the genesis of willed actions and required in situations where the routine selection of actions was unsatisfactory - for instance, in dealing with novelty, in decision making, in overcoming temptation, or in dealing with danger" (Shallice, 1988, p335). It therefore follows that the supervisory system concept is central (a) to human problem solving, and (b) to the deterioration of same following brain injury. [For further details, see Norman (1990) and our e-papers on Resource Allocation Theory and Mode Error in System Control.]
Nuclear Membrane: This is the outer surface of the cell nucleus, that is to say, the layer which confines the nucleoplasm. Outside the nuclear membrane there is cytoplasm. It is a two-layered molecular structure, namely a bimolecular lipid layer (lacking the outer "sandwich" of protein layers which characterises the cell membrane).
Nucleolus: (Pl: Nucleoli.) This is a small spherical shaped structure, of which one or more may be present within the nucleus. It consists mainly of RNA, and is where ribosomes are first created (that is to say, prior to their migrating out into the cytoplasm and making their way to the walls of the endoplasmic reticulum).
Nucleoplasm: This is the fluid medium of the cell nucleus. It contains the nucleoli and the chromosomes. [Compare cytoplasm and interstitial fluid.]
Nucleus: This is physically and functionally the central component of the cell. It is a near-spherical structure, containing the nucleoplasm, the nucleoli, and the chromosomes, and is bounded by the nuclear membrane. Most cells have a single nucleus, although muscle cells have several and red blood cells have none.
Object: Apart from its everyday usage, the word "object" also has a specific technical meaning within the "object-oriented" field of computing [see our e-paper on "Short-Term Memory Subtypes in Computing and Artificial Intelligence", Part 6 (Section 3.9), if interested in this aspect of memory theory].
OAT: See Object Alternation Test.
OAT-PE: See Object Alternation Test.
Object Alternation Test (OAT): This is a test first devised for use with animals (e.g., Pribram and Mishkin, 1956) and then adapted for use with humans (Freedman, 1990). It requires the integration of short-term visual memory and simple rule learning. The patient is seated in front of two black "plaques", either, both, or neither of which can be used to cover over a small object such as a coin. The patient thus has to learn the rule, but can perseverate with said rule once it has been established. The perseveration score may be abbreviated to OAT-PE. Poor performance on the OAT is usually associated with lesions of orbitofrontal cortex (Freedman, 1990).
Organelle: A subcellular structure (or class of structures), such as the Golgi apparatus, the mitochondria, or the ribosomes.
Orienting: Maintaining general everyday awareness. One of the first things to be established in the Routine Neurological Examination is "orientation to time, person, and place". This involves asking such questions as "Do you know where you are, Ethel?", "Can you tell me who the Prime Minister is?", and so on. Orienting can therefore be regarded as one of the all-pervading components of intact and effective executive function, because it helps establish attention in the first instance, and thereafter makes both planning and execution-monitoring more appropriate.
Orthodromic Conduction: The propagation of a neural impulse in the "forwards" direction, that is to say, from a point of stimulation on the axon away from the cell body. The opposite of antidromic conduction.
Partial Report Paradigm: A memory test set-up in which subjects are presented with an array of test items, but required to process only a subset thereof. This involves cueing before, during, or after the display with instructions as to which subset is to be recalled. Providing the cue is received early enough, this allows advantage to be taken of sensory memory resources as well as more centrally situated STM. [For probably the most famous application of this method, see Sperling (1960).]
Perception: This is the name given to the process by which information acquired from the environment is transformed into experience of objects and events (Roth and Frisby, 1986). It is a selective placing of input into one category of identity rather than another (Bruner, 1957), thus making it essentially an act of categorisation [see category]. This act of categorisation seems to take place in discrete stages, culminating with access to perceptual memory.
Perceptual Memory: [See firstly perception.] This is LTM for external stimulus pattern (primarily visual or auditory). Its contents help you recognise things you have interacted with in the past (particularly familiar faces and objects), and this act of recognition is at the heart of the process of "perception". The visual input lexicon (which gives you the ability to recognise the words in this sentence at high speed), and the auditory input lexicon (which gives you the ability to segment incoming speech) are both further examples of memory for external stimulus pattern. In turn, perceptual memory supports a rich array of higher perceptual and thought processes. For example where more than one external object is involved, perception does its best (a) to identify all of them, (b) to locate them appropriately in three-dimensional space, (c) to flag them appropriately (as friend or foe, perhaps), (d) to attribute intention to them and to raise predictions as to their imminent behaviour, and (e) to track their subsequent actual behaviour against said expectations. [See now imagery.]
Perseveration: [See firstly frontal battery.] An inability to discontinue (i.e. cancel) an ongoing planned behaviour, despite instructions to do so, and a common feature of dysexecutive syndrome. Perhaps a failure of the mind's contention scheduling mechanism.
Phonological Recoding Effect: [See firstly Working Memory Theory.] This is the name given to the recruitment of both the phonological loop and the articulatory loop memory resources for material initially presented to the four senses other than hearing (i.e. vision, touch, smell, and taste). It reflects our ability (indeed preference) for naming non-auditory stimuli, thereby increasing the likelihood of their safe retention.
Similarity Effect: [See firstly confusibility
studies.] This is the name given to an STM impairment when presented with acoustically
similar material. It was first detected by Conrad (1964), who found that misrecollections of target letters were more likely to be
acoustically similar than not. Thus "D" would be more commonly an
error for "B" (with which it rhymes) than for "R" (with
which it does not rhyme). Where consonant sequences were to be memorised,
Planning: Although planning is strictly speaking a cognitive process, not a form of memory (i.e. it is something the mind does, not something it contains or creates), it is nevertheless a process which requires memory, (a) to store its primary products (i.e. the plans), (b) to store the action schemas needed to enact said plans, (c) to put the whole experience away in episodic memory once completed, and (d) to update the indexing of that new memory as appropriate.There seems to be no final and all-embracing theory of planning, although Schank and Abelson's (1995) scripts, story memories, and event memories present a neatly integrated package, and Chevignard et al (2000/2003 online) are working on identifying and integrating the memory components involved in executive function.
Post-Synaptic: Generally relating to the neuron on the "down" side of a synapse.
Post-Synaptic Membrane: [See firstly cell membrane.] The receiving (or "down") side of the synaptic cleft.
Post-Synaptic Potential: Refers to the electrotonic effects at the receiving neural cell membrane when the neurotransmitter substances arrive. Can be inhibitory or excitatory (i.e. it can either discourage or encourage a further action potential in the receiving neuron).
Post-Tetanic Potentiation: The reduction of the action potential threshold for a short period following a given action potential.
Potential: The presence of ions at a given point. Loosely speaking, the same thing as "voltage".
Potential Difference: A difference in potential between two points; a "slope" of potential between these two points; a potential gradient. Potential gradients are important because ions tend to "flow down" them until the potential difference is cancelled out. This is what is happening whenever a current is flowing. This is similar to the concepts of concentration and concentration gradient, but is driven by electrostatic forces rather than random molecular movement.
Potential Gradient: See potential difference.
Pragmatics: The science of communicational motivation, that is to say, of the effects that immediate motive, context, and custom have on discourse. [For further details see the longer entry under the same heading in our Psycholinguistics Glossary.]
Pre-Synaptic: Generally relating to the neuron on the "up" side of a synapse.
Pre-Synaptic Membrane: [See firstly cell membrane.] The transmitting (or "up") side of the synaptic cleft.
Price Estimation: [See firstly executive function and dysexecutive syndrome.] A test of executive function requiring subjects to estimate the cost of named items (jumbo jet. diamond ring, bag of sugar, etc).
Primacy Effect: [See firstly serial position effect.] Superior performance on the early list items in a free recall learning task. [See serial position effect and compare recency effect.]
Priming: The act of pre-exposing subjects to memory test material prior to the memory test proper being applied. This might involve something as simple as deliberately pre-using items from a word list prior to the delivery of that list (item priming), or of pre-presenting semantically related items (semantic priming) or phonologically similar items (phonological priming). Priming typically improves subsequent memory recall, and so failure to benefit from a particular type of priming can often indicate an underlying pathology [as seen, for example, in Nation (2001)].
Proactive Interference: A type of interference, specifically, the deleterious effect of previous memory contents on newly memorised material. [Contrast retroactive interference.]
Procedural Memory [definition; discussion]: This is memory for sequential performance. It is the sort of memory which needs to be retrieved when you are faced with time-extensive tasks such as making a cup of tea, carrying out a long division, or safely administering an injection. Educationally, it is one of the most important types of memory, because it is at the heart of being able to do things; it is the sort of memory where - having once been shown how to carry out a sequence of tasks - that sequence becomes internalised as some sort of mental computer program, so that you find yourself thinking: "you do this, then this, then this .....", and so on. It is conceptually similar, if not identical, to the scripts and stories of the Schank and Abelson tradition, and overlaps with knowledge management units and action schemas.
Prompting: See cueing in our Neuropsychology Glossary.
Propagation: The movement of a depolarising influence from one point on a neural cell membrane to adjacent points. Can be of two types, namely decremental propagation and non-decremental propagation. Decremental propagation is the term used to describe minor fluctuations in resting potential which fail to reach the threshold necessary for an action potential to develop, and which rapidly die away. Non-decremental propagation is another term for the spike discharge action potential. What makes the action potential highly biologically significant is that a depolarisation at one point on the cell membrane somehow affects the metabolic pumping at the immediately adjacent point. The term voltage-dependent gating is often used to describe the fact that the metabolic pumps which set up the potential difference in the first place are themselves sensitive to changes in that potential. This results, in turn, in an action potential developing at that adjacent point, which affects the area next to that, and so on in a ripple effect. This gives a viable basis for the transmission of information from one point in a biological system to another.
Proposition: [See firstly predicate and proposition in our Psycholinguistics Glossary.] A proposition is that which describes a particular truth relationship between concepts [e.g., "cats have fur"], and which is thus "the smallest unit of knowledge that can be judged either true or false" (Matlin, 1989). It follows that propositions must exist either within, or close to, semantic memory, because that (by definition) is where all the concepts are stored. [Now compare the constative and the performative types of speech act in our Psycholinguistics Glossary.]
Propositional Knowledge: [See firstly proposition.] Knowledge made up of propositions. Also known as "declarative" knowledge.
Prospective Memory (PM): Prospective memory is memory for events which have yet to happen, that is to say, it is "the ability to remember at a particular moment that one has previously decided to carry out a particular action at that moment" (Raskin, 2003 online), although Elvevag, Maylor, and Gilbert (2003/2003 online) add the proviso "without any explicit prompting to recall". Prospective memory is therefore an association between future cue and future action. The cue may be arriving at a particular moment in time or location in space, or the occurrence of a particular triggering event (i.e., "time-", "location-", and "event-based" PM, respectively). The theoretical complexities of "intention as a distinct form of memory" were first noted by Kvavilashvili (1987), and have inspired considerable empirical research ever since (e.g., Ellis, 1996). The faculty itself has been attributed to the frontal lobe as an adjunct to the planning process. It is possible that prospective memory is also involved in the execution of multiple future actions not covered by a suitable procedural memory, nor script. This would presumably be the sort of skill assessed by the Activities of Daily Living Test of executive ability. PM might also involve some sort of right hemisphere "time line", with NOW in the middle, one's past stretching away in the PAST direction, and one's ambitions and plans for the future suitably sequenced at points in the FUTURE direction. PM is also increasingly being treated as one of the cognitive abilities wherein a deficiency might legitimately constitute a cognitive deficit, that is to say, where the construct itself may help explain a special educational need or mental health problem of some sort. For example, Kliegel, Ropeter, and Mackinlay (2006) have studied its correlates with attention deficit/hyperactivity disorder, Warren et al (2007) have done the same with type 1 diabetics, Woods et al (2007) have done the same with HIV positives, Cockburn (e.g., 1996) has done the same with brain injured patients, and Kumar, Nizamie, and Jahan (2005) have studied event-based PM in schizophrenia, and report this ability to be "poor" compared to matched non-psychiatric control subjects. The UK government, moreover, has recently recognised that PM needs to be screened for when assessing autistic spectrum disorder, but there is little yet in the literature regarding this line of enquiry.
Protein Kinase Studies: [See firstly electrochemical medium-term memory.] Successful neurotransmission relies in large part on enzymes which can phosphorylate - that is to say, add a phosphate group to - other proteins, thus changing their molecular shape, electrical charge, and overall properties. They are fairly abundant in brain tissue, where they are heavily involved in second messenger neurotransmission. Though there are many types of protein kinase, two of them in particular seem to be triggered, or "primed", by the presence of calcium ions, that is to say, they are "calcium-dependent". These are calcium/calmodulin-dependent kinase (type II) (or Cam/K II, for short), and protein kinase C (or PKC, for short). Both Alkon (1989) and Levitan and Kaczmarek (1991) provide detailed descriptions of these triggering processes to which the specialist student may refer. In essence, however, what happens is that both PKC and Cam/K II - once triggered - will migrate outwards from post-synaptic cytoplasm to post-synaptic membrane, and there - over a period of many minutes - act to adjust the ease of subsequent potassium ion (K+ ) transfer across that membrane. In other words, they generally enhance the "receptivity" of the post-synaptic neuron to all subsequent stimulation. Levitan and Kaczmarek describe this sensitising process as providing the neuron with a "calcium-switch" (p239), by which relatively long-lasting changes to a neuron's properties can be turned on and off. Another recent paper summarises its importance this way: "The protein kinases [activated by calcium ions] are now thought to govern many types of slow (or modulatory) synaptic mechanisms and to mediate many forms of short-term synaptic plasticity. These processes, which do not depend on the synthesis of new proteins and can endure from minutes to a substantial part of an hour ....." (Schwartz and Greenberg, 1987, p459.) [For a broader introduction to this topic, see our e-paper on "The Neurobiology of Memory".]
Random Access: Computer terminology for long-term data storage systems from which specific data items can be retrieved without serial search. Random access can be achieved in a number of ways, as described in some detail in our e-paper on "Short-Term Memory Subtypes in Computing and Artificial Intelligence", Part 5 (Section 3.1).
Random Molecular Movement: The particles making up gases and liquids are continually moving about at very high speeds. This allows them, when they are bounded by a permeable (porous) membrane, to find their way through to the other side. Moreover, once they are on the other side, some of them find their way back in again! Depending on how many holes there are, and how big they are relative to the size of the particles, this process takes more or less time to come about. In the end, however, the density of particles on one side of the membrane will be the same as on the other. In gases, this process is known as diffusion, and in liquids it is known as osmosis.
Readiness Potentials: A readiness potential is a strong negative shift in parietal EEG in the moments immediately prior to the initiation of a voluntary response, almost as though the brain were "winding itself up" in readiness to go off. This effect was first detected by Kornhuber and Deecke (1965). A typical study by Libet et al (1983) found a negative shift on average 350 msec. prior to the movement beginning. The impact has been summarised as follows: "These experiments at least provide a partial answer to the question: What is happening in my brain at the time I am deciding on some motor act? It can be presumed that during the readiness potential there is a developing specificity of the patterned impulse discharges in neurons so that eventually there are activated the correct pyramidal cells for bringing about the required movement." (Eccles, 1977, p111.)
Recall: [See firstly the three fundamental physical memory types described in the Introduction.] Retrieval into STM, especially that part of it we know as consciousness. If from LTM not recently accessed, then presumably with the help of processes like ecphory, indexing, or similar retrieval structure. If from more recently accessed LTM (i.e. electrochemical medium-term memory), then presumably by "touch-and-glow" neuronal sensitisation by second messenger neurotransmission. [Compare recognition.]
Recency Effect: [See firstly serial position effect.] Superior performance on the late list items in a free recall learning task. [See serial position effect and compare primacy effect.]
Receptor Sites: Points on the post-synaptic neural cell membrane where neurotransmitters can "bind" chemically, and thus cause post-synaptic potential to appear.
Recognition: [See firstly recall.] Form of LTM retrieval involving awareness of past encounter, such as when having to judge words or pictures as having previously been presented.
Reductionism: [See firstly explanatory gap.] A philosophical doctrine predicated upon the assertion that complex sociocultural and psychological phenomena can ultimately be explained in terms of underlying chemical or physiological processes [and far from universally supported].
Reductionist: Follower of Reductionism as a philosophical school and set of explanatory principles.
Refractory Period: [See firstly action potential.] Period of inexcitability at a given point on the neural cell membrane during the repolarisation phase after an action potential. Helps (a) to limit the number of times per second that a given neuron can fire, and (b) to prevent antidromic conduction.
Rehearsal: The repeating of memory test material to oneself, either out loud or subvocally using the faculty of inner speech. Explicitly suppressed by the interpolated activity task(s) in studies using the Brown-Peterson technique to investigate the serial position effect. In fact, Craik and Lockhart (1972) proposed two types of rehearsal, namely maintenance rehearsal (also known as "Type 1" rehearsal), where items circulate within a given processing level, and elaborative rehearsal (also known as "Type 2" rehearsal), where each repetition deepens the level. Increasing the amount of maintenance rehearsal does not influence later recall. Allowing or encouraging elaborative rehearsal, on the other hand, seems to assist recall in two ways, firstly by making the stimulus in some way distinctive, and secondly by multiplying the number of associational links to the stimulus. [Compare context rehearsal.]
Relationship: The interaction between the entities dealt with by a system [source]. Alternatively, "the way in which two or more entities are dependent on each other" (Kramer and de Smit, 1977:15). "A relation exists 'if a change in a property of one entity results in a change in a property of another entity'" (Kramer and de Smit, 1977:16; italics original). [See now Entity-Relationship Modelling.]
Repression: The psychodynamic theory of forgetting. Holds that memories can be deliberately lost/suppressed if they contain ego-threatening material.
Allocation Theory: See dedicated
support article. Resource Allocation Theory is
Resting Potential: The neural resting potential is an electrostatic potential difference between the inside of a cell (the cytoplasm) and its surrounding fluid medium (the interstitial fluid). It arises from the operation and interaction of three complex and conflicting factors, namely random molecular movement, metabolic pumping, and electrostatic forces. In a typical neuron (in common with all other types of cell), there is naturally more protein in the neuroplasm than there is in the interstitial fluid. The opposite is true of salt (NaCl). Both types of molecule ionise, the protein into potassium cations (K+) and protein anions (protein-), and the salt into sodium cations (Na+) and chlorine anions (Cl-). This creates FOUR separate concentration gradients (one for each of the ion types) along which ion movement would normally be expected. All these particles "want" to balance their inner and outer concentrations, but they are physically of different sizes, so their natural osmotic speeds will vary (negligible, in fact, for the large protein anions because they are the biggest of the lot) . At the same time, there is active metabolic pumping going on within the neuron membrane, with thousands of sodium pumps pushing the sodium ions back out as fast as they can. And thirdly there are the electrostatic forces of ion attraction and repulsion. If you leave things alone, however, the flows rapidly stabilise into an equilibrium, where the numbers of each ion inside and outside the cell stays constant, but not necessary equal. There will, for example, be a difference in the Na+ count due to metabolic pumping, and as a result the net charges inside and outside the cell are different. This gives rise to an electrical potential difference between the intracellular and extracellular fluids, and because this potential difference, once established, remains constant, it is known as a resting potential. A cell's resting potential can thus be defined as the difference in electrical potential across its cell membrane when ion movements inwards and outwards are in equilibrium. The resting potential for a typical neuron is -70mV.
Retrieval: The act of accessing the information stored in memory.
Retroactive Interference: A type of interference, specifically, the deleterious effect of newly memorised material on previous memory contents. [Contrast proactive interference.]
Retrieval Structure: See long-term working memory.
Ribosome: This is a small granular organelle, of which several thousand may be present in a given cell, congregating especially on the membranous walls of the endoplasmic reticulum. It is the place where single molecules of protein can be synthesised.
Rote Learning: [See firstly Bloom's Six Levels of Knowledge.] Learning lists or definitions "off by heart" (that is to say, with little concentration on understanding). A good method of surface learning, therefore, and of little practical utility in the modern world.
Routine Neurological Examination: Portfolio of simple bedside tests [e.g., orienting] carried out by doctors, etc., as part of everyday healthcare in order to screen for or assess nervous system problems.
Saltatory Conduction: [See firstly resting potential and action potential.] A biologically cost-efficient method of rapid conduction of an action potential along a myelinated axon, by allowing it to "jump" from one node of Ranvier to the next. The point is that the myelin sheathing of the axon between each node of Ranvier prevents depolarising effects across the cell membrane, whilst the tube of cytoplasm within the axon is capable of bringing the adjacent node of Ranvier to its action potential threshold. Conduction thus takes place without the biochemical expense of a continuously propagating action potential.
Schema: Although little is known about the mind's way of representing propositional knowledge, two approaches have been particularly influential over the years. The first of these is the very long-standing Associationist tradition, and the second is Head's (1926) concept of the "schema". The former derives ultimately from ancient Greek philosophers such as Aristotle, regards knowledge as consisting of a massively interlinked network of individual ideas, and lives on as a tradition in modern network models of long term memory. Schema theory, on the other hand, emphasises the role of superordinate cognitive structures in understanding. It does not deny the existence of concepts as such, nor the importance of associations between them, but it looks up a level at how subsets of concepts are habitually organised by "an active organisation of past reactions, or of past experiences" (Bartlett, 1932, p201). Schemas predict what will happen to things in the future from how those things (or similar things) have behaved in the past, and the schema tradition has been brought up-to-date in a number of guises, including Thorndike's (1977) "story structures". [Compare story memory and script theory.]
Schwann Cell: An oligodendrocyte, that is to say, a glial cell with relatively few cell processes, responsible for the myelination of neural tissue (myelin is a protein-phospholypid derived from the oligodendrocyte's cell wall).
Script: [See firstly story memory.] Within the context of Schank and Abelson's theories, a script is "a structure that describes an appropriate sequence of events in a particular context" (Schank and Abelson, 1977, p422). Alternatively, it is an expectation "about what will happen next in a well understood situation" (Schank and Abelson, 1995, p5), thus "[obviating] the need to think" (p6). Sometimes referred to as an "event schema", and often equated with the planning component of executive function (whereupon it needs to be followed up by a period of script execution).
Script Execution: [See firstly script and executive function.] Chevignard et al's (2000/2003 online) term for the execution-and-monitoring component of executive function (which, incidentally, they suspect is a better index of dysexecutive syndrome than tests of planning per se).
Script Recitation Task: [See firstly executive function and dysexecutive syndrome.] DETAIL TO FOLLOW. Godbout and Doyon (1995).
Script Theory: [See firstly script and script execution.] Schank and Abelson's analysis of memory structures.
Second Messenger Neurotransmission: [See firstly neurotransmission.] There seem to be two classes of receptor site involved in successful neurotransmission. The protein molecules making up the ion channels are directly coupled receptors, and are structured so that the neurotransmitter molecule can bind directly with them, thus instantaneously influencing their gating properties. Indirectly coupled receptors, on the other hand, are situated some distance away from the ion channels, respond more slowly, and - in some instances, at least - operate by having the neurotransmitter molecule release what is known as a G-protein from the inner wall of the post-synaptic membrane. This G-protein then migrates through the post-synaptic cytoplasm and opens up ion channels "from the inside". Moreover, if one neurotransmitter molecule can manage to release several G-proteins it allows the transmitted signal to be amplified accordingly. Most neurotransmitter receptors are of the indirectly coupled type (Levitan and Kaczmarek, 1991). G-proteins are thus examples of what are known as second messenger neurotransmitters. The first messenger is the transmitter substance which actually crosses the synaptic gap: the second messenger, on the other hand, is any substance - and there seem to be many - activated by the initial binding. These substances diffuse inwards through the cytoplasm of the post-synaptic neuron and seem to be responsible for two major biochemical events. The first of these is concerned with propagating the action potential (because it is, after all, one of the tasks of an excitatory neurotransmitter to induce an EPSP, thus bringing the post-synaptic neuron closer to its own action potential threshold), and the second is to sensitise the neuron in question to subsequent stimulation. [Compare first messenger neurotransmission and see Yin (1999/2003 online) for technical back-up.]
<< AUTHOR'S NOTE: One of the main points of all this technical detail is that as far as memory is concerned, any process capable of outlasting a momentary depolarising event and selectively facilitating subsequent transmission might conveniently subserve a memory of that event. Accordingly, "touch-and-glow" second messenger sensitisation could well deliver the sort of "short term continuity of consciousness" described in the Introduction, and seen in our ability, say, to repeat the early items in a short memory span list as soon as the last one has been heard without any need for rehearsal. >>
Selective Permeability: EITHER a cell membrane where the pores are not big enough to allow all particles through, OR a membrane where metabolic pumping is taking place. The nerve membrane is semi-permeable because it allows small ions through but withholds the large protein anions: it is also semi-permeable because it contains the sodium pump.
Self-Ordered Pointing Test: [See firstly executive function and dysexecutive syndrome.] The Self-Ordered Pointing Test is a simple test of the integrity of the working memory support component of human executive function, and, as such, is commonly included as a frontal battery test. The test was developed by Petrides and Milner (1984), and presents patients with a set of 6, 8, 10, or 12 card stimuli, "each bearing a regular array of stimulus items, the relative position of which varied from card to card" (p404). They are then required to go through the card set touching the same stimulus (in its different positions) on each. The presumed processing load is described as follows: "This meant that subjects had to keep track of their own past responses while actively planning the ones to come" (p404).
Semantic Memory: This is the name commonly given to our mental storehouse of conceptual (i.e. encyclopaedic) knowledge. As our perceptual memory and episodic memory gradually grow during infancy, they give rise to memory for meaning, thanks to the process of abstraction. For example, by the time an infant has seen a pen making marks on paper three or four times it begins to get the idea - the "concept" - that that is what a pen "is for": if it only had the language, it would be able to define things accordingly - "pen - something for drawing with", "draw - something you do with a pen", and "paper - something you draw on with a pen". Semantic memory thus ends up containing everything we know about the world. Moreover, in normal development, the growth of semantic knowledge coincides with sustained and highly focussed exposure to naming and language shaping from parent(s) and/or carer(s). The end result of all this is a powerful network of concepts and propositions, cleverly linked to a repertoire of symbols - words - contained in the auditory input lexicon. The separation of knowledge and word (i.e. concept from symbol) has been fundamental across psychology since the 19th century, and comes across particularly well in Freud (1891). [See now the next six entries.] Here is a handy definition .....
"Semantic memory is the associative network of permanent knowledge about the world built up over a lifetime, including knowledge of the rules of language and its lexicon or vocabulary [citations]. Access of information from this permanent memory system occurs continually during all types of cognitive processing." (Ober and Shenaut, 1988, p273.)
- Associative: [See firstly semantic memory and association.]
The problem with semantic memory is that it soon acquires many thousands of
unitary concepts. Another very basic neural process then takes place, allowing
the association of concepts, one with another, turning what began as a simple
concept store into one vast, interlinked, concept web, just as the Associationists described. Example:
<Blackpool - tram>, <orange - clockwork>, and <
Semantic Memory - Categorical: [See firstly semantic memory.] The process of abstraction also allows regularities amongst concepts to be detected, thus creating higher order classificatory concepts. Example: <swallow> similar <sparrow> similar <rook>, thus creating the need for a category header <bird>. There is a lot of evidence to suggest that categorical memory is another major "right hemisphere" skill. [See, for example, the "right hemisphere hypothesis of dyslexia" in our e-paper entitled "Dyslexia and the Cognitive Science of Reading and Writing".]
Semantic Memory - Propositional: [See firstly semantic memory and proposition.] It is also possible for agent and object concepts (nouns) to join with action concepts (verbs) to create simple assertions of truth such as "Tom is a cat" and "mice chew gloves". These are known as propositions, and propositions are what start to turn LTM into knowledge as we know it. As you successfully acquire more and more of them, your conceptual memory becomes "propositional" (sometimes "declarative" [definition]) memory, and your mind begins to get very good at reasoning and problem solving. [Now compare predicate in our Psycholinguistics Glossary.]
Semantic Similarity Effect: [See firstly confusibility studies and semantic memory.] This is the name given to an LTM impairment when presented with semantically similar material. It was first detected by Baddeley (1966), who found that semantically similar sequences such as "large-great-huge-long-big" were more prone to recall error after 20 minutes than semantically disparate sequences such as "old-wet-strong-thin-deep". He also detected a weak semantic similarity effect in STM. [Now compare phonological similarity effect.]
Semantic Network: See semantic memory - associative.
Semantic System: Broadly speaking, a combination of pragmatics, semantic memory, and executive functions. [See the longer entry on this heading in our Psycholinguistics Glossary.]
Sensory Memory: Very short-term memory for input pattern or attribute, within a particular perceptual channel. Visual sensory memory tends to be referred to as iconic memory, and auditory as echoic memory.
Serial Position Curve: See serial position effect.
Serial Position Effect: [See firstly Brown-Peterson technique.] This is the name given to the characteristic U-shaped curve obtained by plotting the probability of retrieval of an item from a series against its position within that series. The raised wings of the U reflect distinct memory advantages to the early and late items. The relatively good recall of items from the beginning of the list is called a primacy effect, and the relatively good recall of items from the end of the list is called a recency effect. The recency effect, in particular, is extremely vulnerable to the introduction of an interpolated activity distractor task, presumably because the recency advantage only existed in the first place due to the ability of late-list items to be selectively rehearsed.
Six ElementsTest: [See firstly executive function and dysexecutive syndrome.] The Six Elements Test is a simple test of the integrity of the planning-execution components of human executive function, and, as such, is commonly included as a frontal battery test. The test was developed by Shallice and Burgess (1991), and requires the subject to carry out six "open-ended tasks" in a 15-minute time slot. The tasks are divided into two sets of three of equivalent difficulty [to allow before-and-after testing without advantage], and the tasks themselves are (1) dictating a route, (2) carrying out 35 arithmetic problems, and (3) naming 100 objects from picture stimuli. [Compare Multiple Errands Test.]
Slave Systems: [See firstly Working Memory Theory.] Term introduced by Baddeley and Hitch (1974) for the hypothetical structures which provide specific (as opposed to ad hoc) memory resources to the central executive. Two specific slave systems were proposed, namely the articulatory loop and the visuo-spatial sketchpad.
Sodium Pump: [See firstly cell membrane and metabolic pumping.] A sodium pump is a complex molecular tube spanning all four layers of the neural cell membrane. It operates by taking sodium ions from the neuroplasm, transporting them along its length, and depositing them outside the cell in the interstitial fluid, and is thus a major mechanism in setting the resting potential of the cell in question. It is switched on and off by a voltage-dependent gating process.
SOPT: See Self-Ordered Pointing Test.
STEV [Project Konrad]: An event giving rise to momentary electrical activity within the brain. [Compare MTEV]
Story Memory: Schank elevates the story, and everything which goes with it - story telling, story understanding, and story reconstruction - to a position of central importance in human cognition: all our knowledge, he argues, "is contained in stories and the mechanisms to construct them and retrieve them" (Schank and Abelson, 1995, p2). Schank and Abelson warn that there is no single way to understand a given story, because it can be fitted into any one of several possible story skeletons. They see understanding as "mapping your stories onto my stories" (p16), and indexing as the key to finding a suitable story from one or more suitable levels. Thorndike (1977) offers an interesting "building block" approach to story analysis, which is more or less compatible with Schank and Abelson's proposals.
Suggestibility: A measure of individual differences in the susceptibility of eye-witness testimony to planted false elements.
Supervisory System: [See firstly central executive and Resource Allocation Theory.] Term coined by Norman and Shallice (1980) in their discussion of the cognitive mechanisms of planned action, and one of the basic proposals of the resulting Norman-Shallice Model of Supervisory Attentional Function. The model proposes is a three-layer/five-box control hierarchy (similar to Craik, 1945), sculpted on top of a sixth box containing the schema selection process. This latter process is characterised as relying as much on inhibitory mechanisms as upon excitatory, so that the momentary salience of one motor program comes in large part from a carefully synchronised lack of "contention" from all the others (Shallice, 1982, p200). As such, the model potentially has a lot to say about the phenomenon of "control modes" in behaviour. Control modes were first proposed in the early 1980s (e.g., Norman, 1981), and are significantly broader in scope than schemas. In fact, each control mode has four important qualities, namely (a) that it controls a repertoire of related lower level motor programs, (b) that it has competing modes, (c) that these competing modes can be momentarily inhibited, and (d) that when it itself has been activated it will therefore possess a behavioural momentum of some sort. Each mode, in other words, is "a manner of behaving" (Degani, Shafto, and Kirlik, 1995/2003 online).
Surface Learning: [See firstly Bloom's Six Levels of Knowledge.] Term coined by Marton and Saljo (1976a,b) to characterise the relatively mindless learning of lists and repetitions. [Contrast deep learning.]
Symbols: A symbol is that which "stands for" something else. Words are symbols for concepts, and concepts are themselves representations of this or that external entity. Naming a concept allows one to communicate it to others, although for the recipient(s) of a name to attach precisely the same meaning to that concept as you did relies upon them having precisely the same concept structure as you. [Compare concept.]
Synapse: A junction between two neurons. The point where a synaptic button from the transmitting (or "pre-synaptic) neuron touches the neural membrane of the receiving (or "post-synaptic") neuron. Each neuron receives synaptic input from many other neurons. [See also synapse, locations and synapse, mechanisms.]
Synapse, Locations: The pre-synaptic neuron at a given synapse can touch the post-synaptic neuron at any point, and there are names to describe the various options.
Synapse, Mechanisms: Synapses are the sites where chemical neurotransmission takes place. Whether a given neurotransmitter has an excitatory or an inhibitory effect depends upon the chemical reaction at, and therefore the nature of, the binding site. Acetylcholine, for example, has an excitatory effect on skeletal muscle fibres, but an inhibitory effect on heart muscle. [See also Dale's Law.]
Synaptic Button: Enlargement of the axon or telodendrion of a pre-synaptic neuron at the point where it butts against the post-synaptic neuron.
Synaptic Cleft: The gap between the two neurons at a given synapse.
Synaptic Learning: The creation of networks of neurons to act as engrams by linking them together via their synapses. One of the first to suggest that learning was accompanied by the formation of new synaptic connections was Santiago Ramon Y Cajal (e.g., 1911). The general idea was that synapses made it possible for neural pathways to connect themselves up on demand - that is to say, as learning took place. Pathways could thus appear where previously just disconnected neurons had existed. Moreover, the biological act of creating those pathways underpinned the psychological act of memorising the experience in question.
Synaptic Vesicle: Small "bubble" filled with neurotransmitter within the neuroplasm of a synaptic button. When an action potential arrives it prompts these vesicles to move to the surface of the cell where they burst and release their contents into the synaptic cleft.
Tests of Planning in Daily Life: [See firstly executive function and dysexecutive syndrome.] See Activities of Daily Living Test.
TMT: See Trail Making Test.
Trail Making Test (TMT): [See firstly executive function and dysexecutive syndrome.] This test was devised by Reitan and Wolfson (1985), and requires patients to join up specified sequences of letters and/or numbers printed randomly across a test page. The test comes in two parts. Part A requires only that patients connect a sequence of numbers, say in ascending order. Part B, however, requires that numbers and letters be connected alternately in ascending order, and provides the better test of frontal performance (Stern and Prohaska, 1996, p252). The TMT is one of the Halstead-Reitan subscales, and is good measure of attention maintenance.
Transcoding: [See firstly encoding.] Term popularised by McCarthy and Warrington (1984) to describe the act of changing from one basis of encoding to another during information processing, a process which is clearly seen in the Ellis (1982) flow diagram. [See now transcoding model.]
Transcoding Model: A box-and-arrow model of the longitudinal cognitive system, which attempts to identify (a) the processing modules involved, and (b) the points where transcoding takes place. If restricted to the language processing system, the model in question necessarily has to show inputs separate from outputs and spoken language separate from written, giving it a characteristic X-shape. The classic example of a language transcoding model is Ellis and Young (1988), although much the same layout can be seen in the mental modularity proposed for mathematical cognition.
Transference: This term is used by eye-witness memory theorists to refer to the crossed allocation of correctly remembered actions to correctly remembered agents, thereby creating a false memory.
Triplex Model of Memory: [See firstly consolidation and Duplex Model of Memory] Any "three-box" model of memory which separates sensory memory, STM, and LTM. Better known as the Modal Model of Memory.
Utilisation Behaviour: A clinical sign of impulsivity deficit in dysexecutive syndrome. Attempting to pick up and use lure objects, despite instructions not to. Indicates that perceptual stimulation is being routed to, and capable of activating, motor schema selection processes WITHOUT going through any higher control process.
Very Short-Term Memory: Same as sensory memory.
Viewpoint: This term is used by eye-witness memory theorists to refer to difficulties recognising faces (in a police line-up, say) when they had previously been seen from a different angle/height/distance/illumination, thereby creating false positive or false negative identifications.
Visual Input Lexicon: Term popularised by Ellis and Young (1988) for the mental storehouse for whole textual word forms. [For further details see the longer entry under the same heading in our Psycholinguistics Glossary.]
Visuo-Spatial Sketchpad Subsystem: This is Baddeley and Hitch's (1974) second proposed slave system [the first being the articulatory loop]. It is the hypothetical structure which allows you to "rehearse pictures", as it were, and its key emphasis is accordingly upon the role of imagery in memory. Now the point about imagery is that word referents are not equally "imageable" - when considering how they might be encoded, you need to know their position along the concrete-abstract continuum. Thus "nudist" (a concrete noun) is easier to visualise than "intellect" (an abstract noun). It is not surprising, therefore, to find that imagery is an important memory variable. Atwood (1971), for example, tested memory for highly imageable phrases against memory for low imageable phrases, and found that interpolated visual activity interfered with the former whilst interpolated auditory activity interfered with the latter. Similarly, Baddeley (1986) found that performance on a pursuit rotor was degraded more by a visual memory task than by a verbal memory task. He also reported that if eye movements were controlled during memory tasks by forcing subjects to attend to stimuli moving on a TV screen it would disrupt a spatial memory task requiring imaging. He concluded that the imaging system - the "visuo-spatial sketchpad" - can hold spatial and patterned information for a short time, but fails quickly when time and sequence are introduced, or when eye movements are otherwise directed.
Voltage-Dependant Gating: This is the sensitivity of a neuron's sodium pumps to the membrane potential surrounding them, the point being that the pumping (or "gating") only carries on while said potential is within pre-set limits. When the local potential reaches the action potential threshold, the metabolic pumping suddenly shuts down, and an action potential immediately develops.
Weigl Colour-Form Sorting Task (CFST): [See firstly executive function and dysexecutive syndrome.] This test is described in Section 5 of our e-paper "From Frontal Lobe Syndrome to Dysexecutive Syndrome".
WFT: See Word Fluency Test.
WMG: See working memory, general.
Word Length Effect: See articulatory loop.
Word Fluency Test (WFT): This test is described in Section 5 of our e-paper "From Frontal Lobe Syndrome to Dysexecutive Syndrome".
Working Memory, General (WMG): [See firstly Working Memory Theory.] This is Baddeley and Hitch's (1974) general purpose STM resource. It is the hypothetical structure which sits alongside the two slave systems in the service of the central executive. Unlike those slave systems, however, it is not possible to predict in advance the nature of the stored information, and so WMG is a close approximation to the use of working storage in electronic digital computers [as fully reviewed in our e-paper on "Short-Term Memory Subtypes in Computing and Artificial Intelligence", Part 6 (Section 3.3)]
Working Memory Theory (WMT): Term/theory introduced by Baddeley and Hitch (1974), inspired metaphorically by the working storage facility provided in electronic digital computers [as fully reviewed in our e-paper on "Short-Term Memory Subtypes in Computing and Artificial Intelligence", Part 6 (Section 3.3)]. WMT was proposed as an alternative to the then extant Modal Model of Memory, because it dealt more effectively with STM phenomena. The theory proposed two fixed-purpose and one general-purpose STM resources (the slave systems and the working memory, general) and a control structure called the central executive. WMT has been popular ever since, although it has recently been getting stiff competition from the Norman-Shallice Model of Supervisory Attentional Function. One particularly fascinating application of WMT is Calvin's (1983) study of aimed throwing behaviour, wherein it is argued that the precise timing of motor activity is a major consumer of scarce neural resources. Another is its use in the minds of Air Traffic Controllers [reading], and another is Gathercole's (1990) research linking working memory skills to the development of literacy skills in children.