Post on 23-Dec-2015
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
Neuropsychology of MemoryNeuropsychology of Memory
• Memory problems following TBI– post-traumatic amnesia– retrograde amnesia– anterograde amnesia
Neuropsychology of MemoryNeuropsychology of Memory
• 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
Neuropsychology of MemoryNeuropsychology of 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
Neuropsychology of MemoryNeuropsychology of Memory
• 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
Neuropsychology of MemoryNeuropsychology of Memory
• 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)
Neuropsychology of MemoryNeuropsychology of Memory
• 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
Neuropsychology of MemoryNeuropsychology of Memory
• 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
Neuropsychology of MemoryNeuropsychology of Memory
Recall of information from PZ autobiography
01020304050607080
1916-1930
1930-1940
1940-1950
1950-1960
1960-1970
1970-1980
Per
cen
t re
call
Recall
Neuropsychology of MemoryNeuropsychology of Memory
• 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
Neuropsychology of MemoryNeuropsychology of Memory
• 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)
Neuropsychology of MemoryNeuropsychology of Memory
• 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
Neuropsychology of MemoryNeuropsychology of Memory
• Amnesic syndrome– dense form of memory deficit (as assessed by
standardized testing)– relatively spared performance in other domains
Neuropsychology of MemoryNeuropsychology of Memory
• 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.
Neuropsychology of MemoryNeuropsychology of Memory
• 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
Neuropsychology of MemoryNeuropsychology of Memory
• 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
Neuropsychology of MemoryNeuropsychology of Memory
• 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:
Neuropsychology of MemoryNeuropsychology of Memory
• 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.
Neuropsychology of MemoryNeuropsychology of Memory
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.
Neuropsychology of MemoryNeuropsychology of Memory
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?
Neuropsychology of MemoryNeuropsychology of Memory
– 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
Neuropsychology of MemoryNeuropsychology of Memory
– 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)
Neuropsychology of MemoryNeuropsychology of Memory• HM, Hippocampal man
• 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
Neuropsychology of MemoryNeuropsychology of Memory
• 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
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
Neuropsychology of MemoryNeuropsychology of Memory• HM, Hippocampal man
• 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.
Neuropsychology of MemoryNeuropsychology of Memory• HM, Hippocampal man
• 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
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
Neuropsychology of MemoryNeuropsychology of Memory• HM, Hippocampal man• Dot pattern study (Gabrieli, 1990,
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
Neuropsychology of MemoryNeuropsychology of Memory• HM, Hippocampal man
• 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
Neuropsychology of MemoryNeuropsychology of Memory• HM, Hippocampal man• Dot pattern study (Gabrieli, 1990,
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
Artificial grammar learningArtificial grammar learning
• 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
Artificial grammar learningArtificial grammar learning
• 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
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
–
Recognition memory: dual-process models
Recognition memory: dual-process models
• 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
Recognition memory: dual-process models
Recognition memory: dual-process models
• 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
Recognition memory: dual-process models
Recognition memory: dual-process models
• 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
Neuropsychology of MemoryNeuropsychology of Memory
• Functional characteristics of amnesia– working memory is intact– semantic memory is spared (controversial)– episodic memory is impaired– procedural memory is intact
Neuropsychology of MemoryNeuropsychology of Memory
• 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
Neuropsychology of MemoryNeuropsychology of Memory
• 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
Neuropsychology of MemoryNeuropsychology of Memory
AutonoeticEpisodic
Semantic
Procedural
Noetic
Anoetic
Neuropsychology of Declarative Memory
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
Neuropsychology of Declarative Memory
Neuropsychology of Declarative Memory
• Medial temporal lobe structures viewed from the side (saggital section)
• Moscovitch et al. (2005)
Neuropsychology of Declarative Memory
Neuropsychology of Declarative Memory
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
Neuropsychology of Declarative Memory
Neuropsychology of Declarative Memory
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
Neuropsychology of Declarative Memory
Neuropsychology of Declarative Memory
Brain regions mediating declarative memory: flow of 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
Neuropsychology of Declarative Memory
Neuropsychology of Declarative Memory
Brain regions mediating declarative memory: flow of information
– 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
Neuropsychology of Declarative Memory
Neuropsychology of Declarative Memory
Brain regions mediating declarative memory: flow of information
– 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
Neuropsychology of Declarative Memory
Neuropsychology of Declarative Memory
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
Neuropsychology of Declarative Memory
Neuropsychology of Declarative Memory
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
Neuropsychology of Declarative Memory
Neuropsychology of Declarative Memory
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)
Neuropsychology of Declarative Memory
Neuropsychology of Declarative Memory
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.
Neuropsychology of Declarative Memory
Neuropsychology of Declarative Memory
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
Neuropsychology of Declarative Memory
Neuropsychology of Declarative 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