Disorders of Memory
David Groom
Introduction to Cognitive Psychology
Chapter 7
Anterograde Amnesia
• Impairment of memory since onset of
amnesia.
• Failure of encoding (learning)
Tests
Retrograde Amnesia
Impairment of memory for events occurring
before the onset of amnesia.
Temporal gradient (Ribot’s Law)
Remote memories tend to be preserved,
whereas recent memories are lost.
Found in most types of organic amnesia
Focal AA and RA
• In general, both AA and RA are found in
organic amnesia.
• Rare cases in which there is only AA or only RA
• Focal AA damage is confined to Anterior
Thalamus.
• Focal RA damage to temporal lobe
Organic Amnesia
- Several Causes (share hippocampal damage)
- Difficulty consolidating new memories (AA)
- Generally some difficulty retrieving past
memories (RA)
- Intact STWM (able to carry on conversations)
- Normal digit span (7 items) and recency effect.
- Irreversible
Areas of Brain
that play a role in AA
Temporal Lobes
Hippocampus
Diencephalon
A cluster of subcortical structures in the center
of the brain. For memory, the most important
are the thalamus and the mammillary bodies.
Areas of the Brain
that play a role in RA
Prefrontal Cortex
Temporal Cortex (Cortical areas that include the
hippocampus)
Extended Hippocampal complex
- Thalamus, Mammillary bodies (Diencephalon)
and Hippocampus.
- Encoding and Consolidation
Alzheimer’s
e.g., Ronald Reagan
• Degenerative Disorder - slow decline in
memory, thinking and reasoning skills.
Ten Signs
• Memory loss that disrupts daily life
• Challenges in planning or solving problems
• Difficulty completing familiar tasks at home, at
work or at leisure
• Confusion with time or place
• Trouble understanding visual images and
spatial relationships
• New problems with words in speaking or
writing
• Misplacing things and losing the ability to
retrace steps
• Decreased or poor judgment
• Withdrawal from work or social activities
• Changes in mood and personality
Korsakoff’s Syndrome
Lack of vitamin B1
- common in people with alcoholism.
- malabsorption disorders
- chronic illness or after bariatric surgery.
- AIDS, Long-term dialysis or of intravenous (IV)
therapy
-Extreme nausea vomiting (e.g., during
pregnancy)
Symptoms of Korsakoff’s syndrome:
• Inability to form new memories
• Loss of memory, can be severe
• Temporal gradient - the more remote the event in the
past, the better it is preserved and the sharper the
recollection of it.
• “Living in the Past”
• Making up stories (confabulation)
• Seeing or hearing things that are not really there
(hallucinations)
• Damage to the thalamus and the mammillary bodies
Herpes Simplex Encephalitis (HSE)
Clive Wearing
• Type I, II, Epstein-Barr virus, varicella-zoster
• Sudden on-set
• Very young and elderly or immune
compromised.
The Case of HM
• Bilateral Medial Temporal
Lobectomy
– Removed his medial temporal
lobes (MTL) bilaterally to
alleviate serious epilepsy
(1953)
• Hippocampus
• Amygdala
• Rhinal Cortical Areas
– Epilepsy improved
– He was last patient to receive
this treatment
• After surgery:
– Intellect was above average
• IQ actually improved from 104 to 118
– Normal perceptual and motor abilities
– Well-adjusted individual
– He was left with very poor memory abilities
–Mild retrograde amnesia
(~ 2 years prior to surgery)
–Profound anterograde amnesia
• HM is the most famous patient in the history of
neuroscience research.
• He has served as an invaluable teacher of the
neurobiology of memory and has been extensively
tested for over 50 years.
• Demonstrated that the medial temporal lobe is
critical for forming new memories.
• Video of HM
- Died in 2010
Tests For Retrograde Amnesia
Boston Remote Memory Test
Famous Faces
Free recall portion: patients asked
to recall the name of the person
shown in the photograph (e.g.,
Telly Savalas). Participants were
given ample time to respond.
If they were unable to recall the
name, were given a series of cues.
First, a semantic cue was given
(e.g., "He was an actor, American,
and had a popular series on TV").
If semantic cue fails a phonemic cue was given
(i.e., the person's initials).
Four answer, forced choice test.
(e.g., Yul Brynner, David Soul, Don Rickles, or
Telly Savalas).
Past Public Events Test
Performance measured with a free recall test
(e.g., "Who killed John Lennon?") and a fouralternative, forced-choice recognition test
(names of individuals such as John Hinkley, Sara
Jane Moore, David Roth, or Mark Chapman).
Both of these tests involve Semantic (fact based)
as well as episodic memory.
Autobiographical Events
(Personal Events)
Primarily of Episodic memory but some
autobiographical semantic components.
Often difficult to assess the accuracy.
Theories of Amnesia
Encoding (Consolidation) Deficit Theory
- AA due to a failure of encoding of new
material.
- RA due to an undetected encoding failure
prior to diagnosis. (RA is actually due to AA)
- this is possible for gradual onset disorder
(Alzheimer’s & Korsokoffs) but does not
explain RA in sudden onset cases (HSE &
Temporal Lobe Surgery).
Korsakoff’s Patient P.Z.
(Butters & Cermak,1986)
P.Z. was an eminent university professor and
scientist who had written his autobiography
shortly before the onset of the clinical
appearance of his disease.
P.Z. had classic graded retrograde amnesia in
which the events over five decades leading up to
the clinical appearance of the disorder showed a
systematic decline in recall.
Encoding (Consolidation) Deficit Theory
Explanation
One explanation of P.Z.’s RA is that the disorder
impaired consolidation of memories during a
time prior to the diagnosis of Korsakoff’s
syndrome, so that what appeared to be RA was
really the long-term effects of AA.
Using his own biography, the investigators were
able to test P.Z.’s memory for events in his life
beginning in his early years, through his
undergraduate and graduate training, and into
his career and family life beyond.
Found recently acquired information, even was
more vulnerable to interruption than more
remote memories – suggesting a retrieval
problem in RA.
Retrieval Deficit Theories of Amnesia
Retrieval impairment produces both AA and AR
Problems:
- Predicts AA and RA should be equally as sever
in patients (and this is not true).
- Difficult to explain Focal AA and Focal RA
Separate Disorders of Encoding and
Retrieval
Consolidation Model
Consolidation has two stages
- immediate – takes only a few seconds
- longer – continues to strengthen trace for
two of three years
- hippocampus
- episodic turned to semantic
Variation in RA Periods
Some patients have very long-term RA (30 years
in the case of the Korsakoff’s patient presented)
Some have very limited (HM only few years)
Consolidation model can not explain these
differences.
Multiple Trace Theory
Hippocampus is involved in converting episodic
to semantic (encoding). Once semantic, the
memory is independent of the hippocampus.
Retrieval of episodic memories requires the
hippocampus.
Predicts that episodic memory for all time
periods should be disrupted, but only recent
semantic memories should be impaired.
Explaining the Temporal Gradient
of RA
• Older memories have more retrieval routes.
• Are more resiliently consolidated
• Older semantic memories are independent of
the hippocampus.
Motor Skills
Old motor skills tend to be
retained and new motor skills can
be learned (procedural memory)
but they lack knowledge that they
have learned the new skill (no
declarative memory for the
procedure).
Newly learned skills do not
generalize.
Implicit Memory
• Degraded Pictures test
• Many patients with organic amnesia are able
to do as well as normal on implicit memory
tasks while doing much poorer on explicit
tasks.
Episodic and Semantic Memory
In general, episodic more severely impaired than
semantic in Organic Amnesia patients.
Familiarity and Context
Organic Amnesic persons are able to tell that
an object, place or person are familiar even
when they do not recognize the context from
which it is familiar.
Huppert and Piercy (1979) study
Babies Alternative
Declarative and Non-declarative
Organic amnesia patients are more impaired in
declarative (consciously controlled) than nondeclarative (automatic - implicit memory,
procedural memory & familiarity).
Hippocampus may be needed to “bind” a
memory with its context.
Non-declarative memory depends more on the
cortex and the cerebellum.
Impaired STM
Associated with Frontal Lobe Lesions
Difficulty with contextual information
- know facts, but not why they know them.
Schacter et al. (1984)
Presented facts
Remembered facts, but not where they learned
them. Often confabulated where they learned the
facts.
Impairment of Central Executive of
Working Memory
Confabulation: Filling in memory gaps with a
falsehoods that a person believes to be true.
Tendency to use Semantic information to fill in
episodic or autobiographical memory. Failure of
the executive function to verify the source or
the context.
Normal Aging and Memory Loss
Decline in recall but not recognition .
Decline in explicit but not implicit memory.
Difficulty recalling contextual information.
- source of the information
- time of the event.
Related to frontal lobe loss
Concussion Amnesia
Most common cause of amnesia
Anterograde amnesia (difficult to
form and retain new memories).
Amnesia is sometimes not
noticeable until a few days or even a
week after an injury or accident.
e.g., sports player who retains
detailed memories of what was
happening during a game before an
injury, but who has no recollection
of what happened subsequent to
the incident.
Generally, this is temporary.
Retrograde amnesia tends to be for a minute or
two before the trauma (but could be days or
weeks). Generally, this is permanent.
Normal STM (e.g., digit span)
Temporary inability to consolidate memories.
Memory Strategies for Amnesiacs
“Spaced” rather than “massed” learning.
Leaning in various contexts.
Mnemonics
Errorless learning
External Aids
- lists, simple written instructions
- higher tech gadgets (pagers, alarms &
cameras).
Psychogenic Amnesia
(functional or dissociative)
- severe stress or psychological trauma
Global amnesia - (fugue state)
- sudden loss of personal identity
- severe stress or depression
- extended periods of wandering and confusion.
Very rare, and usually resolves over time (although
memory of the fugue episode itself may remain
lost).
Situation-specific amnesia
- type of psychogenic amnesia that occurs as a
result of a severely stressful event.
- normal autobiographical memory processing
blocked by imbalance of stress
hormones (e.g., cortisol) particularly in the
regions of the limbic system.
- often difficult to distinguish a true repressed
memory from a false one without
corroborating evidence.