Memory

Lecture 3

Overview

• What have patient case studies told

us about the nature of memory?

– Episodic vs semantic memory
– Amnesia
– Implicit/explicit tasks

Types of memory

Episodic vs. Semantic

Memory

Tulving (1972, 1983):

LTM consists of

two distinct yet interactive systems

– Episodic Memory
– Semantic Memory

The case of Gene

– Motorcycle accident at 30
– Preserved intellectual functioning

Episodic vs. Semantic

Memory

Schacter (1986)

– Golfing with Frederick
– Alzheimer’s disease

Vargha-Khadem et al (1997)

– Premie Jon
– hippocampal & temporal lobe damage

Double dissociation?

Squire & Zola-Morgan (1998)

• NO!
• Just because Jon performs adequately in
school does not mean his semantic
memory has not been affected.

• Needs to be tested with more sensitive
measures

Episodic vs. Semantic

Memory

Episodic vs. Semantic

Memory

DeRenzi et al. (1987): Italian woman

• caught encephalitis at 44
• remembered familiar people, but...
• trouble remembering meaning of words
• a ‘complement’ to Fred & Jon.

Imaging

• Pretty good evidence for different

mechanisms
NOT CONCLUSIVE!

Huntington’s disease

• Damage to the structures in the

brain called basal ganglia

• Preserved declarative memory

Summary

• Distinction between semantic and

episodic memory processes

• Not a clear distinction but evidence

that they are distinct yet interactive
systems

• Difficulty is also due to individual

differences – no two patterns of
damage will be the same

• Limits the ability to generalise from

single case-studies

Amnesia

• Can a whole life become unconscious?

– Simulated amnesia

(Schacter, 1986)

• Loss of memories or memory abilities

beyond what is expected in the normal

course of forgetting

• Normal intelligence, normal attention span

(O’Connor, Verfaellie & Cermak, 1995)

• Organic and functional psychogenic amnesia

Psychogenic amnesia

• Memory loss due to an experience which

does not cause brain damage but which
nonetheless results in abnormal
forgetting

• Pathological and Non-pathological types

– Pathological types occur in association with

dissociative mental disorders

– A disturbed integration of memory,

consciousness and/or identity

Psychogenic amnesia

• Hallmark feature is (retrograde)

amnesia for some or all ‘personal
history’

• Dissociative amnesia

• Dissociative fugue

• Dissociative identity disorder

Dissociative Disorders

• Collecting autobiographical

memories

(Schacter et. al., 1989)

• Case I.C.

– 4 ‘alter egos’, all aware of each other

and I.C.

– I.C. is unaware of the other four.
– A ‘recency bias’ combined with almost

no memories for events up to age 12

Organic amnesia

Neurophysiological

– Organic damage to the brain
– Retrograde and anterograde

• Causes of retrograde

– Closed head injury
– Strokes/cardiovascular incidents
– Alcohol (Korsakoff’s syndrome)

Explicit vs. Implicit Memory

• Explicit (Declarative) memory

• Implicit (non-declarative) memory

Schacter (1987,p501)

– "information that was encoded during a

particular episode is subsequently
expressed without conscious or
deliberate recollection"

H.M.

• Epileptic Seizures
• Bilateral medial temporal lobe removal

– Including hippocampus

• Memory prior to surgery = ok

• Severe ANTEROGRADE amnesia

– Every new moment = new & fresh
– Any delay between presentation & recall

= impaired

H.M.

• Doesn’t know where he lives, who

cares for him, what he ate at his last

meal, what year it is, who the

president is, how old he is…

• In 1982, failed to recognize picture of

himself on 40

th

birthday

• BUT, can learn some new things and

not know it

– Mirror-drawing task
– Classical conditioning*

H.M.

HM

• Severe anterograde
• Intact STM
• Explicit memory impaired
• Implicit learning (mirror drawing)
• Initially retrograde seemed fairly

preserved (Milner et al, 1968)

• Later testing – only first 15 years
• HM defined amnesia

KC

• KC changed it all
• Initially seemed ‘just like HM’
• Severe anterograde, preserved

retrograde

• But KC could not recall any personal

events

• Similar to HM?

(Corkin, 2002)

• MTL & hippocampal damage
• Intact perception, language & reasoning

skills

• Lacked ‘autonoetic’ awareness

KC

• Trait knowledge of himself but missing

the ‘remembrance’

(Tulving, 1993)

• Managed to learn ‘gist’ knowledge

– Gist events in his life are semantic facts

• More complex than HM
• Can learn new semantic knowledge
• Similar to RS
• KC recognises himself in photos but

has no memory of the events

KC

• Diffuse and multi-focal damage

• Helped to change the way that we

thought about memories

• Semantic/episodic/autobiographical/s

patial memories

Task Dissociation

• Evidence that explicit and implicit

memory are distinct systems comes
from dissociations using two types of
tasks

– Explicit Tasks:

– Implicit Tasks:

Task Dissociation

• Warrington & Weiskrantz (1970)

– Participants

• Amnesic patients
• normal controls

– Presented participants with lists of words
– Memory tasks

• Explicit tasks

– Free recall
– Recognition

• Implicit tasks

– Word fragment identification (e.g., participants had to

identify visually degraded words)

– Word stem completion (e.g., complete the stem: bo__)

Perceptual skills

Summary

• Case studies of amnesia have greatly

enhanced our understanding of

memory processes

• Underlying brain areas, types of

memory, characteristics, interaction

• Also, the development of cognitive

tests (implicit vs explicit) has increased

our understanding of memory

processes in amnesia

• Understanding of memory is

sometimes limited to the individual –

difficulty generalising due to individual

differences

• Schacter, D. L. Feeling-of-knowing ratings distinguish

between genuine and simulated forgetting. J. exp.
Psychol.: Learn. Mem. Cognit. 12, 30~,1,1986.

• ELIZABETH K. WARRINGTON
• Studies of retrograde memory: A long-term view

http://www.pnas.org/cgi/reprint/93/24/13523.

pdf

• Schacter, D. L. (1987). Implicit memory: History and

current status. Journal of Experimental Psychology:

Learning, Memory, and Cognition, 13:501--518.

• Rosenbaum, Kohler, Schacter, Moscovitch,

• Westmacott, Blackb, Gao &Tulving (2005). The case

of K.C.: contributions of a memory-impaired person to

memory theory. Neuropsychologia 43 989–1021