A-Z of Memory

John Aggleton is a world-wide recognised researcher and author. He has published over 300 papers, principally on brain systems devoted to different forms of memory. His contribution to the field was recognised by the Royal Society in 2012 when he was elected as a Fellow. He has also served as President of the British Neuroscience Association and of the European Brain and Behaviour Society. He is currently Emeritus Professor of Cognitive Neuroscience at Cardiff University.

• IntroductionA) Absent-minded – being forgetful, often from a failure to pay attention to one’s actions Adaptive memory – that our learning and memory skills are tuned to solving fitness-based problems, reflecting how our memory evolvedAging – the impact of time on an organism once maturity is reachedAlcohol – a chemical (ethanol) with psychoactive effects that is globally used as a recreational drugAlzheimer's disease (AD) – the commonest form of dementia characterised by the presence of brain atrophy, amyloid plaques, and neurofibrillary tangles, along with pronounced cognitive declineAmnesia – the loss of memory despite the sparing of other cognitive abilitiesAmygdala – a limbic brain structure in the anterior part of the medial temporal lobesAnaesthetics – see Unconscious learningAnterograde amnesia – the failure to encode, consolidate, or retrieve new information that would normally reside in explicit long-term memoryAssociative learning – the ability of organisms to make connections between related events in their environmentAutobiographical memory – individual personal episodes along with more general life information that concerns the same individual Autonoesis – see Episodic memory, RememberAvailability heuristic – see Heuristics B)Bartlett – on the contributions of Sir Frederick Bartlett (1886-1969) Bias – how our memories are shaped by learnt expectations and prejudicesBinding – the bringing together of different elements in space and time to create a cohesive entity, be it a sensory percept or a mnemonic representationBlocking – 1) The ability of a previously acquired association to block further associative learning about the same contingency, 2) The ability of an initial (incorrect) recalled item to block the recall of other potential solutionsBottom-up processing – see Top-down processingC)Caffeine – a widely used stimulant with some positive effects on cognition (see also Nootropics)Central executive – a core component of working memory that helps to regulate attention, make decisions, and guide the brief holding of informationChange blindness – see Illusions of memoryChildhood amnesia (also called Infantile amnesia) – the inability to recall or recognise personal events from our earliest yearsClassical conditioning –the associative learning of how one stimulus predicts another Cognitive control – see Executive functionsCognitive enhancers – see NootropicsComprehension and learning – see Understanding and learningConcept learning – see Grandmother cells, Hub and Spoke model, Semantic memoryConditioned taste aversion – the long-lasting, deep dislike of a taste that had been associated with feeling nauseous Confabulation – the fabrication of narratives and other information, often to fill in memory gapsConfirmation bias – see BiasConsolidation – the progressive stabilization of information post encodingConstructivism in memory – the belief that memories reflect our personal understanding of an event, rather than an objective representationContext and memory – how the same contextual cues at learning and recall can benefit retrieval while changed contextual cues can disrupt retrieval Cross-sectional study – see Longitudinal study Curiosity – an intrinsic motivation to seek novel information and so reduce uncertaintyD)Declarative memory – explicit long-term memory that incorporates both semantic and episodic memoryDeese-Roediger-McDermott paradigm (DRM) – using related words or images to create false memories of a never-presented, but closely related itemDefault mode network – the network of brain areas that increases coordinated activity in between tasks, typically when self-reflecting or mind wandering Demand characteristics – the array of cues that convey an experimental hypothesis to the participantDementia – an umbrella term that covers numerous neurological conditions that progressively disrupt brain function and cause the breakdown of multiple cognitive functionsDepression and memory – the impact of major depression on memory Depth of processing – see Levels of processingDevelopmental amnesia – a syndrome of memory loss and memory preservation seen after bilateral hippocampal damage in childhoodDiencephalon – a core brain area largely consisting of the thalamus, subthalamus, and hypothalamusDigit span – see Memory spanDissociative amnesia – see Psychogenic amnesiaDistributed practice – see Spaced trainingDirected forgetting – see Motivated forgettingE)Ebbinghaus – Hermann Ebbinghaus (1850-1909) is principally famous for his systematic studies of rates of learning and rates of forgettingEchoic memory – the brief sensory store for auditory information, including wordsEcological validity – a term typically used when considering how well a set of experimental findings can be generalized to real-world settingsEcphory – when a cue helps trigger the memory of a past eventEidetic memory – an unusually vivid form of visual memory that is highly accurateElaborative rehearsal – the process of considering the meaning of a stimulus and its implications, processes that create additional connections and enhance recallEmbodied cognition – the notion that the way we think is shaped by our bodily perceptions and experiencesEmotion and memory – the interplay between affect and the elements of memoryEncoding specificity principle – see Context-dependent memory and EcphoryEngram – the enduring trace that records a memory and is potentially available for retrievalEpigenetics – how cellular experiences may modify gene expression without altering the underlying (DNA) genetic code Episodic buffer – a subsystem within working memory that provides a two-way bridge with episodic memory and other aspects of long-term memoryEpisodic foresight (Episodic future thinking) – see Future memoryEpisodic memory – our long-term memory for individual events located in a particular time and place (an episode)Errorless learning – a method of teaching in which people are prevented as far as possible from making errors whilst learning a new skill or new informationEvent segmentation – how a continuous stream of activity is broken down into meaningful unitsExecutive functions – an umbrella term for a set of related cognitive skills that help planning, problem solving, and adapting to new situationsExpert knowledge – the superior ability to acquire and retain new information within one’s domain of expertiseExplicit (declarative) memory – the division of long-term memory that holds information over which we have conscious access and awarenessExtinction – the reduction in frequency or intensity of a conditioned response following the removal of reinforcementEyewitness memory – the study of how and when the remembrance of witnessed events may differ from realityF)False memory (syndrome) – personal narratives for events that never occurredFamiliarity principle – see Mere-exposure effectFear conditioning – learning in which a stimulus or context becomes associated with fearFeeling of knowing – a sense of familiarity indicating the presence of a memory that cannot be fully retrievedFlashbulb memory – a vivid, detailed memory of a surprising, emotional event that often includes what the observer was doing when the event occurredForgetting – the absence or error in a memory, whether by inadequate encoding, alteration, erasure, or retrieval failureForgetting curve – the decline in memory over timeFree recall – the recollection of information as it comes to mind without explicit cues or promptsFugue – a temporary loss of personal identity that appears unaccompanied by physical brain damageFuture memory (episodic future thinking) – our ability to imagine or simulate future autobiographical eventsFuzzy trace theory – see GistG)Generation Effect – how self-generated information is remembered better than information that you have read or heardGist – that some memories only capture the essence of an experience, its gistGrandmother cell – a neuron that only responds to a highly specific, complex stimulus (such as one’s grandmother)Grid cells – spatial neurons whose firing fields are organized in a horizontal lattice that covers the environment, with each firing field being equally spaced (forming a grid)H)Habit – a behaviour that can be performed without conscious control or a behaviour that is gradually acquired over many repetitive trialsHabituation – the gradual lessening of a reaction to a stimulus after the repeated presentation of the same or similar stimulusHead-direction cells – neurons that selectively fire when facing a particular direction (‘the brain’s compass’)Hebb – Donald O. Hebb (1904-1985), a Canadian psychologist best known for his pioneering work on neural networks and learningHeuristic – a cognitive shortcut (rule-of-thumb) that aids rapid decision makingHighly Superior Autobiographical Memory (HSAM) (also known as Hyperthymesia) – the ability to retain past autobiographical memories at exceptional levels of detail Hippocampal formation (Hippocampus) – a medial temporal lobe structure that critically contributes to a range of memory functions, including those required for episodic memory and spatial navigationHippocampal replay – see Memory replayH.M. – Henry Molaison (1926-2008) is the best-known and most studied case of amnesiaHomunculus – i) the seductive fallacy of a little human solving problems inside our head, ii) the outline of a human body across our motor and somatosensory corticesHub and Spoke model of semantic memory – a model of how we represent semantic informationHyperthymesia – see Highly Superior Autobiographical MemoryHypnosis and memory – on whether hypnosis can aid the retrieval of memories or disrupt aspects of memoryI)Iconic memory – a brief visual store thought to combine two forms of visual persistenceIllusions of memory – when our recall or recognition of a past event markedly deviates from the real experience Imagery and memory – how a mental pictorial representation impacts on memoryImagination inflation (see also False memories) – how imagining events that did not occur increases the likelihood of believing in their realityImitation (Imitative learning) – social learning that involves copying the actions of others Implicit memory (Nondeclarative memory) – that component of long-term memory which is not consciously accessibleImprinting – whereby an animal learns, during a sensitive period, to confine its preferences to a specific stimulus (typically another individual), class of stimuli, or locationInattentional blindness – see Illusions of memoryIncidental learning – learning that occurs without the explicit intention to learn and memoriseInfantile amnesia – See Childhood amnesiaInstrumental learning (Operant conditioning) – associative learning in which the likelihood or intensity of a response is regulated by its outcomeInterference – competition between similar information that can cause memory errors Irrelevant speech (sound) effect – how background speech or word-like sounds can disrupt ongoing memory tasks and comprehension Isolation effect – see von Restorff effectJ) Jost’s law – see Ebbinghaus, Ribot’s lawK)Korsakoff’s disease (syndrome) – a form of organic amnesia associated with vitamin B1 (thiamine) deficiency, and most often seen in chronic alcoholics L)Latent inhibition – when a familiar stimulus takes longer to acquire a new association than a novel stimulusLearning – at its simplest, learning is commonly defined as behavioral change brought about by experienceLearning-set – learning to learn, so that previous similar problems lead to the acquisition of a rule (learning-set) to help solve the same class of problems Learning styles – a teaching vogue which presumes that students learn better when receiving information in their preferred medium (style), e.g., auditory, visual, or kinaestheticLevels of processing – the concept that the deeper you process information the better it is subsequently rememberedLloyd-Morgan’s canon – see Instrumental learningLongitudinal study – repeatedly testing the performance of the same individual over time Long-term memory – a repository of stored information that persists for minutes, days, or even years (sometimes referred to as secondary memory)Long-term depression (LTD) – although the term can refer to a chronic depressive disorder, here it concerns a process that weakens connections between neurons, often acting in the opposite way to long-term potentiation (LTP)Long-term potentiation (LTP) – the lasting strengthening of synaptic efficacy following pulses of stimulationM)Maintenance rehearsal – see Elaborative rehearsalMammillary bodies – see Diencephalon, Korsakoff’s syndromeMassed learning – see Spaced learningMemory – the meaning of memory Memory in sensitive plants and unicellular organisms, including slime moulds – on whether memory exists in organisms that lack neuronsMemory replay – the reactivation of sequential activity patterns in neuronal assemblies that replays their prior patterns of activity during learningMemory span – a test of short-term memory in which a series of items are recalled in their order of presentation Mental time travel – see Future memory (Future episodic memory)Mere-exposure effect – how, after repeated exposure, a neutral stimulus acquires positive values Metamemory – the introspective ability to monitor your own memory processes, including its content and capabilitiesMethod of loci – A memory aid (mnemonic) that involves making visual images of items to be remembered, and placing these images in a pre-set sequence of visualised locations Mild cognitive impairment – a condition causing memory or other thinking problems that is often, but not always, a transitional phase leading to dementiaMirror neuron – a neuron that increases its activity when performing an action and when observing that same actionMnemonics – effortful cognitive strategies used to improve memoryMnemonists – individuals who possess exceptional memory abilities, whether seemingly spontaneously or by dint of exhaustive trainingMood congruency – see Context-dependent memoryMotivated forgetting – an effortful process that helps us to forget unwanted memoriesMotor learning – see Procedural learningMultiple trace theory (of consolidation and retrieval) – that each retrieval effort creates a new memory trace, as a result of which the hippocampus remains necessary for the consolidation and retrieval of past episodic memories, irrespective of their age N)n-back task – where participants mentally hold a continuous sequence of items while checking for any repeats from a specified number of places (n) back in the sequenceNeurogenesis – the creation of new neurons Nicotine – an addictive drug that activates one of the two major types of acetylcholine receptors (nicotinic) and is thought to influence cognitionNondeclarative memory – see Implicit memoryNootropics (‘Cognitive enhancers’, ‘Neuroenhancers’, ‘Smart drugs’) – chemicals and supplements purported to improve cognition, including learning and memoryO)Observational learning – social learning based on imitation that makes it possible to acquire new behaviours and knowledgeOlfactory memory – memory for smellsOperant learning – see Instrumental learningP)Partial reinforcement extinction effect – see ExtinctionPartial report method – see Iconic memory, Echoic memoryPattern completion and Pattern separation – ‘Pattern completion’ is the process of retrieving a complete memory representation from a partial or degraded cue; ‘Pattern separation’ is the process of segregating similar experiences into distinct, dissimilar representations Pavlovian conditioning – see Classical conditioningPenfield (Wilder Penfield, 1891-1976) – see EngramPerceptual learning – see Expert knowledgePhenotype – the observable attributes displayed by an individualPhonological loop – a working memory subsystem for speech-based soundsPlace cells – neurons that signal a specific location by increasing their activityPrediction error – the mismatch between a prior expectation and the experienced event Preverbal learning – that period of learning by infants prior to verbal communication, typified by other communication skills such as vocalizations, gestures, and eye contactPrimacy effect – the superior recall of the first few items in a sequence Primary memory – see Short-term memoryPriming – when exposure to a stimulus (now ‘primed’) influences our response to a subsequent stimulusProactive interference – see InterferenceProcedural memory – the implicit memory for skills, habits, and cognitive actions that are performed automatically and for which we lack conscious awareness of their underlying natureProspective memory – the cognitive ability to remember to perform an intended action or recall a planned intention at an appropriate future timePsychogenic amnesia (or Dissociative amnesia) – a memory dysfunction, typically involving a loss of personal memories, which arises from psychological stress or trauma yet without detectable brain damage (or damage that could account for the degree of memory loss)Q) Qualia – the subjective conscious experience of a quality or propertyR)Reality monitoring – see Source monitoringRecall – see RememberRecency effect – the superior recall of information presented at the end of a list over those items presented in the middleRecognition memory – the ability to detect the re-occurrence of a stimulusReconsolidation (and Reconstruction) – the process whereby the retrieval of a memory renders it unstable and prone to modificationRecovered memories – see Repression of memoryRehearsal – the mental repetition of an item to prolong its storageReinforcement and Reward – terms describing how pleasant or unpleasant stimuli can influence the likelihood of a preceding actionRemember (Recall, Retrieve) – to access a memory (or past representation)Remember/Know – see Recognition memoryReplication crisis (Reproducibility crisis) – a methodological crisis concerning how many published findings (e.g., in psychology) are difficult or seemingly impossible to reproduce Repression (memory) – the self-removal of a traumatic memory that cannot be accommodated in conscious memoryRetrieval – see RememberRetrieval effect (Retrieval practice effect) – see Testing effect Retroactive interference – see InterferenceRetrograde amnesia – the sudden loss of past memories, typically following a neurological insultRibot’s law (1881) – that in retrograde amnesia, recent memories are more likely to be lost than older memories S)Savants – people who display spectacular feats of memory, the term ‘savant syndrome’ being largely reserved for those who also face neurodevelopmental challengesSavings – using rates of relearning to assess original levels of learning and retentionSchema – an acquired mental framework that guides the interpretation, organization, and recollection of incoming informationScripts – see SchemasSemantic dementia – a subtype of frontotemporal dementia that predominantly affects language skills, in particular, word comprehension and naming Semantic memory – a division of explicit long-term memory that holds general knowledge about the world, including facts, concepts, words, and number meaningsSensitization – when the repeated exposure to a stimulus results in an amplification of responsiveness to that stimulus, and potentially to other stimuliSensory memory – see Echoic memory, Iconic memorySerial position effect – see Primacy effect, Recency effectShort-term memory – a store holding restricted amounts of information over short time periodsSmart drugs – see NootropicsSource monitoring – the cognitive ability to identify the origin of a memorySpaced training (Spaced learning) – how distributed practice results in more effective learning and more durable retentionState-dependent learning (State-dependency) – see Context and memorySuperstitious learning – the mistaken learning that occurs when an action is coincidentally paired with a reinforcerSynaptic plasticity – see Long-term depression and Long-term potentiationT)Taxi drivers (London) – insights into brain plasticity and spatial learning made possible by the unique training demands on London taxi driversTesting effect – how taking tests during the learning phase facilitates later retrieval from long-term memoryTip-of-the-tongue (tip-of-the-finger, tip-of-the-eye) – the feeling that you are on the brink of recollecting a word, but the correct word will not come to mindTobacco smoking – see NicotineTop-down processing (also Bottom-up processing) – how our prior knowledge and expectations influence perceptual and cognitive decisionsTrace decay – that memories get weaker over time, with time being the critical agent of forgettingTransient global amnesia – an anterograde amnesia of sudden origin and brief duration that selectively affects the ability to make or access new memories while sparing other cognitive abilitiesU)Unconscious learning when anaesthetised – evidence that new implicit learning is possible despite being unconsciousUnderstanding and memory – the relationship between depth of understanding and subsequent memory (also see Constructivism, Elaborative rehearsal, Expert knowledge, Levels of processing, Mnemonics, Schemas)V)Visuospatial sketchpad – a subsystem within the multicomponent model of working memory that holds visual and spatial informationvon Restorff effect (Isolation effect) – the enhanced memorability of an item that stands-out from the array by being different or unexpectedW)White matter plasticity – how experience-induced changes to white matter accompany learning Wisconsin Card Sorting Test – see Learning-setWorking memory – a cognitive system with limited capacity and temporary duration that actively holds information making it available for reasoning, decision-making, and planning (a more restricted definition applies to animal working memory)Y)Yerkes-Dodson law – see Emotion and memoryZ)Zebra fish – a model vertebrate species that has optically transparent embryonic and young larval stagesZeigarnik effect – that uncompleted or interrupted tasks are remembered betterAcknowledgements