neuropsychology of memory

Neuropsychology of MemoryNeuropsychology of Memory

• Types of memory problems– a pure amnesia is relatively rare– memory problems commonly occur after a

traumatic brain injury (TBI)TBI results in brain damage of two sorts: lesionstwisting and shearing of brain structures and

damage from bony protuberances of brain, particularly of the temporal lobes


• Memory problems following TBI– post-traumatic amnesia– retrograde amnesia– anterograde amnesia


• Memory problems following TBI– post-traumatic amnesia

after severe TBI, individuals typically lose consciousness

after they begin to regain consciousness, there is often a gradual recovery during which patients have difficulty keeping tracking of and remembering ongoing events, though there may be islands of lucidity and memory


• Memory problems following TBI– retrograde amnesia

refers to difficulty remembering events that occurred prior to injury

the duration of amnesia varies but can extend back for several years

duration of retrograde amnesia typically shrinks as time passes


• retrograde amnesia– duration of retrograde amnesia typically shrinks as time

passese.g., Russell (1959) described case of TBI as a result of a

motorcycle accident1 week post accident patient had lost 11 years of memory

extending back from injury2 weeks post accident patient had last 2 years of memoryabout 10 weeks post injury memories of the last two

years gradually returned


• Memory problems following TBI

• retrograde amnesia– this pattern of results suggests that retrograde

amnesia is a retrieval problem– the pattern of damage/recovery -- from most

distant to most recent -- has been argued by some to reflect a failure of consolidation (Ribot’s Law)


• Memory problems following TBI

• retrograde amnesia– formal testing of amnesics using famous

faces/famous events has shown that there appears to be recall and recognition for old faces/events


• retrograde amnesia– Butters & Cermak (1986) reported a case study

of an eminent scientist (born 1914) who had written his autobiography only two years prior to becoming amnesic

– tested him by asking him questions all drawn from his autobiography


Recall of information from PZ autobiography

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1916-1930

1930-1940

1940-1950

1950-1960

1960-1970

1970-1980

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Recall


• retrograde amnesia– the pattern of results in some individuals appear to

depend upon the nature of the retrieval cue presented– Warrington and McCarthy (1988) showed that an amnesic

patient was impaired when shown faces of famous people and asked to recall them

– however, performance was normal when tested using recognition procedures


• retrograde amnesia (RA)– pattern of memory gradient varies across patients (See

Moscovitch et al. 2006)– If lesion restricted to hippocampus, RA extends back a few

years only– When lesion includes entire hippocampal formation or

extends to adjacent regions, severe ungraded RA (ungraded means that memory loss is equivalent at all time periods since acquisition); some labs have reported graded retroactive amnesia (recent memories are poorer than more remote memories)


• Memory problems following TBI– anterograde amnesia

refers to problems of learning new factsalthough sometimes amnesia is specific to

learning of verbal material (following LHD) or visuo-spatial material (following RHD) amnesia usually affects learning of many types of new information


• Amnesic syndrome– dense form of memory deficit (as assessed by

standardized testing)– relatively spared performance in other domains


• Causes of amnesiaKorsakoff’s syndrome: drinking too much, eating

too little, resulting in a thiamine deficiency and brain damage

damage to brain following viral infection (e.g., viral encephalitis)

lesion to critical brain regions -- e.g., HManoxia following heart attack, suicide attempt, etc.


• Korsakoff’s syndrome– History

1881, a neurologist Carl Wernicke described a syndrome involving ataxia, oculomotor problems (gaze palsies and nystagmus), peripheral neuropathy, and confusion. This condition came to be known as Wernicke's encephalopathy

Korsakoff identified several patients with confusion, confabulation, sensory loss (especially of the feet), and anterograde amnesia


• Korsakoff’s syndrome– Terminology

Ataxia– problems of muscular coordination; e.g., people ‘duck walk’, feet apart, stiff-legged

oculomotor problems (gaze palsies and nystagmus); abnormal eye movements—palsy = paralysis; nystagmus = involuntary rapid eye movements

peripheral neuropathy = functional disturbance of peripheral nervous system


• Korsakoff’s syndrome– History

1901 Bonhoffer realized Korsakoff’s patients had passed through the Wernicke's encephalopathy stage

today syndrome is called alcoholic Korsakoff syndrome. There are seven primary defining features of this disease:


• Defining features of alcoholic Korsakoff syndrome

a. a retrograde amnesia with a temporal gradient (i.e., better preserved memories from the remote than from the more recent past)

b. anterograde amnesia, meaning a nearly complete inability to learn new information from the time of the disease onset onward.


c. confabulation, which is a tendency to "fill in the gaps" of one's memories with plausible made-up stories.

confabulations are rare among chronic Korsakoff patients who've had the disease for more than 5 years. Patients in the chronic stage are more likely to say "I don't know" or remain silent when faced with memory failures rather than to invent stories.


d. generally preserved IQ, including a normal digit span.

e. personality changes, the most common of which is apathy, passivity and indifference

inability to formulate and follow through a series of plans

f. lack of insight into their condition. How can someone with a shattered memory

remember that he has become unable to remember?


– Korsakoff’s syndromeworst impairments are on episodic memory tests,

including list learning of words, figures, or faces, paragraph recall.

relatively preserved semantic memory, including normal verbal fluency, vocabulary, rules of syntax, and basic arithmetic operations

intact sensori-motor memory (mirror tracing, mirror reading, pursuit rotor)

intact performance on implicit memory tests


– Neuropathology of Korsakoff’s syndrome most sources attribute the amnesia to combined

lesions in two diencephalic structures: regions of the thalamus and the mammillary bodies of the hypothalamus

Neuropsychology of MemoryNeuropsychology of Memory– HM, Hippocampal man– prototype of amnesia attributable to hippocampal

damagebilateral mesial temporal lobe resection extending 8

cm. back from the temporal tips, including the uncus and amygdala, and destroying the anterior two-thirds of the hippocampus and hippocampal gyrus, for the treatment of intractable epilepsy in 1954.

surgery led to a permanent, severe anterograde amnesia, limited retrograde amnesia, and normal intelligence.

Neuropsychology of MemoryNeuropsychology of Memory• HM, Hippocampal man

• Perceptual, motor, and cognitive functioning– IQ above average; language function intact,

speech fluency slightly impaired; spelling poor– Appreciation of puns and linguistic ambiguities– Difficulty with some spatial tasks (e.g., could not

use spatial floor plan to navigate through a novel building, but could reproduce a floor plan of family home)


• Memory– Almost no capacity for new learning regardless of

materials (short stories, word lists, pictures, etc.)– But there are certain tasks requiring memory that

are intact in H.M.– Mirror drawing (covered?)

Neuropsychology of MemoryNeuropsychology of Memory• Multiple memory systems perspective

• HM also has a retrograde amnesia; that is, he forgets events that occurred prior to surgery

• His retrograde amnesia is temporally graded: The closer the event to surgery the less likely he is able to recall it

• This finding suggests that the medial temporal lobes are not always required to retrieve memories (One possibility is that some process occurs that makes it possible to retrieve information that does not rely on medial temporal lobes)

• Long-term memory consists of all the different types of memory shown in the previous slide

• Explicit (declarative) memory refers to memory that can be declared or described to other people

• It includes episodic memory, memory for events in our personal past. Episodic memories are temporally dated, spatially located, and personally experience

• semantic memory, our general knowledge about things in the world


• Multiple memory systems perspective• In 1962 Milner and colleagues showed that HM

improved on tasks requiring skilled movements• HM’s improvement was comparable to controls• Skill was called ‘mirror tracing’ because it requires

participants to draw the outline of a star while looking at the reflection of his hand and the star on the mirror

• HM from had no conscious recollection of having done this task in the past

• This is now viewed as a form of non-declarative or implicit memory tasks

H.M.’s skilled learning performanceH.M.’s skilled learning performance

Encoding and Retrieval from long-term memory (LTM)

Encoding and Retrieval from long-term memory (LTM)

• Multiple memory systems perspective• Other forms of implicit memory include priming

effects that were reported by Warrington & Weiskrantz (1968)

• In this study amnesics shown list of words (e.g., absent); at test participants were given word stem completion task (e.g., abs_____), and instructed to complete with first word that comes to mind

• Results showed that amnesics (and controls) were more likely to complete word stems with previously studied words


• Gollins partial picture task– Task involves recognition of fragmented line

drawings of 20 objects – 5 cards for each object with each card showing

more and more fragments of the completed drawings

– Participants are shown the 20 most difficult cards, then the next-most-difficult cards etc.


• Gollins partial picture task– Task involves recognition of fragmented line

drawings of 20 objects – 5 cards for each object with each card showing

more and more fragments of the completed drawings as shown in Figure

– Participants are shown the 20 most difficult cards, then the next-most-difficult cards etc.

Neuropsychology of MemoryNeuropsychology of Memory• HM, Hippocampal man• Gollins partial picture task (Warrington &

Weiskrantz, 1968 Nature, 217, 972-974– HM and normal controls performed this task, and then

after an hour of intervening activity performed the task again

– Results shown in next figure show that H.M. and controls made fewer errors on immediate tests as figures became more complete and when tested after a 1 hour delay there was memory retention

– Conclusion. Perceptual memory is intact in H.M.; perceptual memory does not appear to be mediated by medial temporal structures

Neuropsychology of MemoryNeuropsychology of Memory• HM, Hippocampal man• Dot pattern study (Gabrieli, 1990,

Neuropsychologia, 28, 417-427)– H.M. and controls were shown a series of 5 dots arranged

in a unique pattern– Baseline draw. Participants (Ps) were instructed to draw

any pattern they wanted (to control for pre-existing biases)

– Experiment. Ps were shown a target pattern & copied that pattern on dots

– After 6 hour delay, Ps were shown dots and were instructed to draw on dots any pattern they wanted


Neuropsychologia, 28, 417-427)

– H.M. and controls were shown a series of 5 dots arranged in a unique pattern

– Baseline draw. Participants (Ps) were instructed to draw any pattern they wanted (to control for pre-existing biases)

– Experiment. Ps were shown a target pattern & copied that pattern on dots

– After 6 hour delay, Ps were shown dots and were instructed to draw on dots any pattern they wanted


Neuropsychologia, 28, 417-427)

– Implicit memory – percentage of target figures drawn that were identical to the copied target pattern (dots drawn in the baseline condition were not scored)

– Explicit memory – Recognition memory – Ps were shown 4 dot patterns that drawn on the dots and selected the dot pattern that had been copied

Dot patternDot pattern

• Top figure shows dot pattern and target stimuli

• Left panel of bottom figure shows explicit performance and right panel shows implicit performance of H.M. and Controls


• Dot pattern study (Gabrieli, 1990, Neuropsychologia, 28, 417-427)

– Implicit memory – dot pattern priming equivalent for H.M. and controls

– Explicit memory – H.M. impaired on recognition memory test compared to controls


Neuropsychologia, 28, 417-427)– Gabrieli and colleagues argued that this finding

cannot be attributable to activation of a pre-existing memory (e.g., a semantic representation)

– Proposed that it is attributable to a type of perceptual priming, perhaps of a non-semantic structural description of a pattern

Artificial grammar learningArtificial grammar learning

• Amnesics can have intact capacity for learning certain cognitive skills

• E.g., artificial grammar such as shown in Figure

• Participants were shown novel letter strings one at a time and were asked to classify the strings as grammatical or nongrammatical


• Participants were then tested to determine whether they could distinguish between grammatical and nongrammatical letter strings

• Results showed that amnesics and normal controls could classify correctly about two-thirds of the letter strings

•

Artificial GrammarArtificial Grammar

• Top panel shows an example of an artificial grammar

• Bottom panel shows examples of grammatical and nongrammatical strings

• Knowlton et al. (1992). Psychological Science, 3, 172-179


• Conclusions– Declarative memory and MTL not required to

encode in memory those processes associated with the encoding into memory artificial grammars

Recognition memory: dual-process models


• Several lines of evidence support the idea that two distinct processes (recollection, familiarity) mediated by different brain regions underlie recognition memory– Example. See face of a person – you recognize the

person as familiar but are unable to recollect anything about the person, when or where you met that person

– Recollection – you recognize that person and can recollect details about that person

–



• Evidence for dual process models (behavioral)– Speeded recognition tests have shown that item

recognition tests (was this item studied) are made more quickly than associative recognition tests (when or where was this item studied)

– Analysis of confidence intervals has shown that when hit rate is plotted against false alarm rate, curves are different for associative recognition (linear) versus item recognition (curvilinear)

– also two different parameters are required to account for shape of curve suggesting that two distinctly different cognitive processes are operating



• Evidence for dual process models (behavioral)– Yonelinas has proposed that familiarity reflects the

strength of the memory trace (an is quantitative)– Recollection reflects retrieval of qualitative, contextual

information



• Evidence for dual process models (lesion)– Amnesics are much more impaired on associative

recognition tests than on item recognition tests– Analysis of confidence intervals has shown that only 1

type of process (curvilinear) is required to account for recognition performance

– See Yonelinas (2002) for further details


• Functional characteristics of amnesia– working memory is intact– semantic memory is spared (controversial)– episodic memory is impaired– procedural memory is intact


• Theoretical implications of amnesia– provides evidence for STM versus LTM distinction– supports the notion that there are different systems

mediating explicit (episodic) and implicit (procedural memory)

– may indicate that semantic and episodic memory can be fractionated

– may provide insight into nature of consciousness


• Memory and Consciousness– Tulving has proposed that different memory

systems have associated with them different levels of consciousnessnoetic -- awarenessepisodic memory -- autonoetic, self awarenesssemantic memory -- noetic, aware of the

information, but not aware of eventprocedural memory -- anoetic no conscious

awareness


AutonoeticEpisodic

Semantic

Procedural

Noetic

Anoetic

Neuropsychology of Declarative Memory


Brain regions mediating declarative memory– what is common appears to be the circuit linking

regions in the temporal lobes, the hippocampus, the mammiliary bodies and regions of the thalamus (note: review Korsakoff’s)

– Next slides will review this in more detail– See Eichenbaum (2002). The cognitive

neuroscience of memory and Moscovitch et al. (2005). 207, 35-66. Journal of Anatomy



• Medial temporal lobe structures viewed from the side (saggital section)

• Moscovitch et al. (2005)

Recollective and familiarity memory systems




Brain regions mediating declarative memory– 3 major component brain regions involved in

declarative memory– Cerebral cortex, parahippocampal region– Hippocampus– Parahippocampal region consists of perirhinal

cortex, parahippocampal cortex, and entorhinal cortex



Brain regions mediating declarative memory: flow of information

– Bidirectional connections between cortex and parahippocampal region

– Bidirectional connections between parahippocampal region and hippocampus

– Highly processed information comes from association areas of the cortex

– Info further processed by the parahippocampal region and hippocampus before being projected back to regions that provided the information




– Aside: Background info about how sensory and motor processing makes its way to association areas

– Sensory info ->primary cortical areas (e.g., visual cortex) -> secondary and tertiary unimodal sensory regions -> multimodal association areas located in temporal, parietal, and frontal lobes as well as in cingulate area




– Aside: Background info about how sensory and motor processing makes its way to association areas

– Motor ->primary cortical area (e.g., motor cortex) ultimately projects to prefrontal and cingulate areas




– Association areas of the temporal -- object identification using info from multiple sensory modalities

– Association areas parietal lobes – process spatial info about visual and other sensory inputs

– Prefrontal and cingulate areas – process info about the significance of stimuli, rules of tasks, and plans for tasks

– Each of these association areas provides input to the parahippocampal region



Parahippocampal region– Consists of 3 distinct areas

Perirhinal cortexParahippocampal cortexEntorhinal cortex

– Inputs to parahippocampal region come from virtually every higher-order association area

– Perirhinal and parahippocampal cortices project to the parts of the entorhinal cortex



Parahippocampal region– Anterior cortical inputs from prefrontal cortex and anterior

cingulate project to the perirhinal cortex and entorhinal cortex

– Posterior cortical inputs (temporal and parietal regions) project to the perirhinal and parahippocampal cortices



Hippocampus– Consists of several subfields including the

CA1, CA3Dentate gyrusSubiculum

– Connected bidirectionally to the fornix, the prefrontal cortex and the parahippocampal region

– Also connected to regions of the thalamus (anterior)



Linking brain and memory– Distinct memory systems reviewed in this lecture include– Recollective memory – conscious recollection of

experiences (autonoetic)– Familiarity memory – memory for stimuli rather than for

events; stimuli are recognized as familiar wthout being placed in spatial/temporal context (noetic)

– Semantic memory – memory for noncontextual content of experience or knowledge about the world (facts, concepts, word meanings, objects, tools etc.)

– It includes knowledge about ourselves (DOB, where we lived, our jobs, facts about family etc.



Linking brain and memory– Recollective memory

Relies on hippocampus, mamiliary bodies, and anterior thalamic nuclei via the fornix (see solid lines in Figure)

– Familiarity memory Relies on circuit involving perirhinal cortex and medial

dorsal thalamusDamage to this circuit will impair recognition of even

single items (see dotted lines in Figure)

– Parahippocampal cortex may mediate place memory



Linking brain and memory– Semantic memory

Does not depend on medial temporal lobe and diencephalic structures

Semantic memory relies on a network of anterior and posterior neocortical structures

Precise structures depend upon attributes of memory (see next slide—different colors represent site of different memory attributes – (e.g., form, motion)

Brain regions include lateral and anterior temporal lobe regions and the lateral inferior prefrontal cortex particularly in the left hemisphere (see next slide)

Martin & Chao (2001). Current Opinion in NeurobiologyMartin & Chao (2001). Current Opinion in Neurobiology

(a) Ventral brain regions from occipital to temporal lobes—represent color and shape properties (fusiform gyrus)

(b) Left lateral areas– motor areas in prefrontal cortex and parietal areas represent manipulation of objects; posterior temporal lobes represent motion properties of objects

Semantic MemorySemantic Memory

neuropsychology of memory

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