3. Memory

Rudolf Cardinalrudolf@pobox.comUniversity Lecturer in Clinical Informatics,Department of Psychiatry, University of CambridgeHonorary consultant psychiatrist, Liaison Psychiatry Service, CPFT & CUH

Cambridge MRCPsych courseTue 23 Oct 2018, pm

MRCPsych syllabus (2018) includes:

Overview

● Memory is the ability to retain information. Very broad term. Perceptual, motor.

● Types of memory and some other key aspects of the psychology of memory.

● Some neurobiology (not comprehensive, e.g. cerebellar memory).

● Some exam-style questions.

Types of memory

Morris (2001), after Tulving

old terms:primary memory = STMsecondary memory = LTM

The ‘sensory store’ — e.g. visual ‘iconic’ memory

P H O G

M Y V Q

X L C U● Brief (50ms) visual presentation → mask → delay → signal to

recall an unpredictable subset. Access to 9–10 letters.● A large amount of information is available for a very short

time (about 0.5s). After this: STM, and access to 4 letters.● Auditory version (“echoic” store): about 2 s.

Sperling (1960)

STM is very S

Miller (1956); Peterson & Peterson (1959)

… and of limited capacity

Miller’s magical number 7 ± 2, digit span, and chunking:

8164912snailcatdogfishthrushbatwormmstoarfhbcadagstnriwtihoulsh

Baddeley & Hitch (1974) model of working memory

● The visuospatial sketchpad and the phonological loop are “slave systems”.

Primacy and recency (serial position) effects

Murdock (1962); Sederberg et al. (2008)

Theories include:● Dual-store models: e.g. primacy relates to LTM storage; recency

relates to STM.● Single-store models: e.g. relating to relative strength of memory

trace; differential rehearsal effects; etc.

recencyeffect

primacyeffect

“40-1” = 40 items for 1 s each

Forgetting: not just decay, but interference by new material?An example (but not a simple one)…

Forgetting and remembering; terms● decay [with time; STM]● interference [by other things]● displacement [from STM]● motivated forgetting [active, even

if unconscious, like ‘repression’]● remembering [vague]

● search / retrieval [from LTM]● recognition [something is

familiar/known]● recall [free, cued] = retrieval +

recognition of recalled item?● retrieval failure / tip-of-the-tongue

state● cue-dependent forgetting / state-

dependent memory● rehearsal● consolidation [STM to LTM] /

reconsolidation [advanced] e.g. Jenkins & Dallenbach (1924)

State-dependent memory

e.g. Abernathy (1940) rooms; Godden & Baddeley (1975) underwater; Duka et al. (2001) drunk

Does the context become part of the memory? Recall is easier if you’re in the same state or context as that in which you learned. Referred to as state-dependency.

Other catchphrase: “cue-dependent forgetting”.

Examples:• room 1 versus room 2• on land versus underwater• sober versus drunk (for tests of explicit memory)

SS same stateDS different stateE encodingR retrieval

Schemata (schemas) and memory distortion

e.g.● Bartlett (1932): Native American

“War of the Ghosts” to UK students, with serial reproduction by each individual.

● Allport & Postman (1947): the passing of stories down a chain of people.

● Treadway & McCloskey (1987): the corruption of the Allport & Postman study by professional psychologists, giving legal testimony relating to eyewitness accounts, who hadn’t read the original.

● memory as active reconstruction● incorporation of existing knowledge● the use of prior knowledge is vital (even for perception)● but can produce distortion to fit existing schema

Episodic versus semantic memory

Semantic memory… categories

Semantic memory: cortical, distributed, related to perception?

Priming

Meyer & Schvaneveldt (1971)

Procedural versus declarative memory

after Dickinson (1980)

Human amnesia

from Markowitsch (1995)

H.M.’s bilateral medial temporal lobe resection on MRI

EC entorhinal cortex, MMN medial mammillary nucleus; A amygdala; H hippocampusCS collateral sulcus; PR perirhinal cortex1953 operation: Scoville & Milner (1957) J Neurol Neurosurg Psych 20: 11MRI: Corkin et al. (1997) J Neuro 17: 3694

H.M. normal brain

Preserved abilities in medial temporal lobe amnesia

Profound anterograde amnesia. Impaired recognition. Some retrograde amnesia (temporally graded).

But• IQ normal• Could learn mirror-writing (Milner 1962, 1965) and similar motor skills day-by-day, despite inability to remember that he’d done it before.• Learned a perceptual learning task (recognition of words from incomplete fragments)• Improved with practice on the Tower of Hanoi task (Cohen 1984)• Short-term memory: normal digit span and visual immediate memory• Priming normal (typical of amnesiacs, see Aggleton & Brown 1999)

McCarthy & Warrington (1990)

The medial temporal lobe: hippocampus, amygdala, fornix

The hippocampal formation in cross-section

Martin (1989, p391)

The hippocampal formation in cross-section (approx.!)

Martin (1989, p391, modified)

(includes entorhinal cortex)

perforant path (EC DG)

The contribution of medial temporal lobe structures

● The delayed non-matching to sample task: which of two objects is new?

● Aspiration of medial temporal lobe structures (esp. hippocampus) impairs DNMTS. So you might think e.g. the hippo. is required.

● But excitotoxic lesions of the hippocampus don’t; the rhinal cortex (includes entorhinal, perirhinal cortex) is critical instead.

● Perirhinal cortex is the first polymodal ventral stream area. It may encode feature conjunctions.

● The hippocampus is important for navigation (place cells; 2014 Nobel Prize [O’Keefe/Moser/Moser]; the hippocampus as a cognitive map; Morris water maze; taxi drivers).

● Also for encoding scenes (monkeys, Raiders of the Lost Ark).● Common role may be relational coding (e.g. what/where/when

conjunction required for episodic memory).

Squire & Zola-Morgan (1991); Murray & Mishkin (1998); Murray & Bussey (1999);Bussey & Saksida (2002); O’Keefe & Nadel (1978); Morris et al. (1982);

Maguire et al. (1997); Gaffan (1992); Eichenbaum et al. (1999)

Long-term potentiation (LTP) as a cellular model of memory

● Glutamate receptor types include AMPA, NMDA

● NMDA receptors are voltage- and ligand-gated

● With sufficient depolarization [postsynaptic activity] plus glutamate [presynaptic activity], they will open and let calcium in, leading to synaptic plasticity.

● Simple mechanism for Hebb’s postulate (cells that fire together, wire together).

● Discovered in the hippocampus (Bliss & Lømo, 1973).

Patient N.A.: fencing foil (up nostril) to diencephalon

(Normal brain! Approximate area of damage in N.A. circled.)

Diencephalon: thalamus, hypothalamus, epithalamus

The Delay–Brion (= Papez) circuit: hippocampus fornix mammillary bodies mammillothalamic tract anterior thalamus

(myelin stain; from Martin, 1991; also Aggleton, 2014)

(posterior hypothalamus; doesn’t connect much with other hypothalamic regions)

(thalamus)

N.B. Wernicke–Korsakoff encephalopathy

Semantic dementia: impaired semantic, preserved episodic? 1

Graham et al. (2000)

mixed task — recognize a different example of an object (‘perceptually different’)

‘episodic’ task — recognize an object (‘perceptually identical’)

semantic task — name a familiar object

Semantic dementia: impaired semantic, preserved episodic? 2

Graham et al. (2000)

normal object recognition;failure to recognize a different example of the same kind of object

impaired semantic performance

a subtype of frontotemporal dementia – the temporal end

Semantic dementia: damage to a simple associative net?

Moss et al. (2002)

computational model

patient with progressivesemantic dementia

Moving memories. Sleep.

● Graded retrograde amnesia following medial temporal lobe lesions.● Gradual transfer of memories from hippocampus/MTL to

elsewhere?● Hippocampus ‘replays’ pattern to cortex, allowing cortical

strengthening?

● Role of sleep.● Hippocampus ‘replays’ activity during sleep.● Sleep aids consolidation of procedural memory (e.g. finger-

tapping sequence).● Sleep aids acquisition of insight into hidden task rules.

Scoville & Milner (1957); Squire et al. (2001);Louie & Wilson (2001); Fischer et al. (2002); Wagner et al. (2004)

Consolidation and reconsolidation

Nader (2003)

consolidation

reconsolidation

● potential use for ‘erasure’ of pathological memories

● old study of conscious ECT for OCD

● consideration of drug/cue-exposure combinations

Habit learning

A double dissociation: Parkinson’s disease and amnesia (1)

Knowlton et al. (1996)

• Task 1 (probabilistic classification): one to three cards are shown. The subject must predict sunshine or rain. Feedback is provided (correct/incorrect). One cue is associated with sunshine on 25% of occasions; one on 43% of occasions; one 57%; one 75%.• Task 2 (declarative): memory for features of the game (screen layout, cues, etc.) is tested with four-way multiple-choice questions.

A double dissociation: Parkinson’s disease and amnesia (2)

Knowlton et al. (1996)

• PD patients: impaired on probabilistic classification task, not declarative. (PD* = severe.)• Amnesic patients (with bilateral hippocampal damage or midline diencephalic damage): impaired on declarative task, not probabilistic classification.

Memory and theprefrontal cortex

Delayed response task: PFC active during the delays

Friedman & Goldman-Rakic (1988); task by Hunter (1913); Fuster & Alexander (1971)

Working memory: PFC maintains posterior cortex activity?

Fuster & Alexander (1970); Fuster (1995)

Two-colour DMTS

Four-colour DMTS

Coloured areas: activity of IT neurons. Black bars: behavioural performance.

Best of five:

Which reflects semantic memory?

A. remembering where you bought your bicycleB. knowing how many wheels a bicycle hasC. being able to ride a bicycleD. remembering where you want to go as you ride your bicycleE. avoiding bicycles because of a near-fatal bicycle accident in

childhood

Best of five:

What is the term for memory that is abstract and independent of the time and place of encoding?

A. workingB. semanticC. episodicD. proceduralE. diencephalic

Best of five:

Which of the following is not part of working memory (Baddeley & Hitch)?

A. Articulatory loopB. Central executiveC. Phonological driverD. Slave systemE. Visuospatial scratchpad

Puri & Ho (2011)

Best of five:

Select one incorrect option regarding schemata:

A. They allow us to ‘fill in the gaps’ when our memories are incomplete.

B. They do not produce significant distortions in memory processes.

C. They have a powerful effect on the way in which memories for events are encoded.

D. They help us to make the world more predictable.E. They provide us with ready-made expectations that help us

to interpret the flow of information reaching the senses.

Puri & Ho (2011)

EMI:

Theories of forgetting(a) Decay theory(b) Displacement theory(c) Interference theory(d) Motivated-forgetting theory(e) Retrieval-failure theory and cue-dependent forgetting

From the above list related to theories of forgetting, select the most appropriate option to which each of the following corresponds:

(i) Tip-of-the-tongue phenomenon.(ii) Ego defence.(iii) Changes in engrams through disuse.(iv) Recall 8 h later of a list of ten nonsense syllables is on

average higher in those who sleep immediately after learning them than in those who stay awake and continue with their normal activities.

Puri & Ho (2011)

True/false for each:

Tests of temporal lobe function include:

A. Seashore Rhythms TestB. Revised Wechsler Memory ScaleC. Left–Right Disorientation TestD. Block DesignE. Object Assembly

McNamara (2003)

True/false for each:

Retrograde amnesia:

A. Refers to memory impairment immediately before injury.B. Is an unreliable index of injury prognosis.C. Is an unreliable index of injury severity.D. Constitutes a disturbance of memory for personal events

and experiences.E. Is considered to arise directly from shear forces within the

brain.

McNamara (2003)

True/false for each:

Duration of post-traumatic amnesia is a good predictor of:

A. Recovery.B. Long-term neurological outcome.C. Long-term psychiatric outcome.D. Occupational outcome.E. Severity of cognitive disturbance.

McNamara (2003)

True/false for each:

The following statements are true with regard to the Wechsler Memory Scale – Revised:

A. Broadly assesses long-term memory.B. Takes less than 1 hour to administer.C. Tests figural memory.D. Tests visual reproduction.E. Tests paired associate learning.

McNamara (2003)

True/false:

A. Episodic memory is usually impaired in semantic dementia.

B. Implicit memory is preserved in Korsakoff’s syndrome.

C. Herpes virus encephalitis is associated with progressive memory loss.

D. The primacy effect is a feature of declarative memory.

E. Verbal recall is affected in right frontal lesions.

F. Progressive memory loss is seen in HIV encephalitis.

G. Procedural memory is not affected in Korsakoff’s syndrome.

H. The hippocampus is supplied by the anterior cerebral artery.

I. The recency effect is preserved in diencephalic amnesia.

J. Retrograde amnesia is the best predictor of outcome in head injury.

Michael & Underwood (2007)