46

Transient Epileptic Amnesia (TEA)/ (TLE) -RA ( ) -AA , . ( ~ 60) ( ) . RA " " . EEG . (ictal state), (postictal state). - -TEA.

8Post-Traumatic AmnesiaTraumatic Brain Injury (TBI)

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, .7MTL - transient cerebral hypoxia ( ) -relational -item recognition. . , MTL 50

Dissociative Fugue (DSM):"" , ( ) .: -0.2% ( ) .- . ( 5=2+2). . .5Dissociative identity disorder (DSM): , . . , . : , . (High hypnotizability) (9:3) () ( -15). .6

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Accelerated long-term forgettingButler et al. Annals of Neurology, 2001 -TEA 10Manes, F. et al. Brain 2001

R.G. (68 years) was asked to produce information about who was shown in the photograph and where and when it had been taken. 1995 1995

R.G.s ability to retrieve specific details associated with the portrayed event (A) or when given verbal description.1011-R.G. , . -TEA (encoding) .

(retrieval)

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TEA- ?11R.G.'s performance on anterograde and retrograde memory tests 13October 1994

February 1995

February 1999

Control mean (SD)Anterograde memory testsStory Recall (WMS-R)Immediate (21)14121112 (4)Delayed (21)1188.59 (3)Rey FigureImmediate (36)35363034 (3)Delayed (36)26261915 (8)Recognition MemoryWords (50)41374047 (3)Faces (50)45414144 (4)Retrograde memory testsFamous FacesRecognition (50)494943 (7)Naming (50)362931 (4)Identification (50)474539 (9)Famous NamesRecognition (50)505050 (1)Identification (50)494949 (1)AMI Personal SemanticChildhood (21)212120 (2)Early adulthood (21)2120.520 (2)Recent life (21)201720 (2)AMI Personal IncidentChildhood (9)897 (2)Early adulthood (9)958 (2)Recent life (9)867 (2)Neuropathology of closed-head TBI15Primary Injury: Contusions/HemorrhagesDiffuse Axonal Injury (DAI)

Secondary Injury (Intracranial): Blood Flow and Metabolic Changes Traumatic HematomasCerebral EdemaHydrocephalusIncreased Intracranial Pressure

TBI ( )

(Irritability) 16

(McAllister, et al, 2000) Warden D, Bleiberg J, Cameron K, et al, 2001

Simple Reaction timeBaseline1 hour post4 days postTBI- (Levin, 1987) (Alexander, 1995)TBI (Collins 2002)17

Bleiberg J., et al. Neurosurgery, 2004.20

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28 KSRetrograde amnesia in Kosrakoff's Syndrome30

Albert et al., 1979 -PI KS33

Cermak et al., 1974361.When did you last ride a bicycle?2.What is a bicycle?3.How do you ride a bicycle?

These questions reveal the different types of long term memories we are capable of accessing.

1. Requires conscious recollection of unique temporally distinct past experience 2. Requires conscious recollection of knowledge, but no unique experienceUnanswerable - unconscious learning

BackgroundThe critical question is whether these types of memories reflect the operation of different memory systems, or whether they reflect different way of accessing a unitary LTS37The episodic / semantic / procedural distinction makes intuitive sense:

Subjects do not forget words - they forget information regarding the fact that the word was presented to them during the experiment. Episodic, semantic and procedural memories are interactive: Learning the meaning of a new word originally requires an episodic memory. Over time the meaning becomes assimilated into semantic memory and the original learning episode may be forgotten Learning to type initially requires episodic memory for the layout of the keys. Over time this becomes redundant The ability to disconnect information from the context in which it was learned is a useful property for a memory system - it saves on storage.Distinction between memory systems38Other research using larger groups of patients with amnesic syndrome demonstrate that they can learn this task as well as controls.Neuropsychological data: - Clive Wearing - still able to play piano and conduct a choir.

BUT can new procedural memories be created in amnesia?

Claparade, 1911: Procedural learning in Korsakoff patient.Patients with amnesia are able to learn a number of tasks, despite having no episodic memory for learning them.Procedural Memory

39Amnesics also demonstrate normal or near normal learning on a wide variety of other tasks.Dress makingFinger mazesJigsaw puzzlesMirror-readingMirror drawing / writingTower of HanoiClosure picturesRepetition priming

However, it is not clear what (if anything) these tasks have in common.Procedural Memory40So what is procedural memory?Moscovitch (1984): Amnesics will do well if:Danger of circularity - learning which is preserved in amnesia is termed procedural...1.It is obvious what is required2.Responses already exist in patients repertoire3.Does not require specific past events to be recalledHowever, amnesics are very slow to learn many things (e.g. programming a personal organiser)Baddeley: There are a number of different types of learning, some of which do not rely on episodic memoryProcedural Memory41Evidence for episodic - semantic distinction:Obvious interdependence of two memory systems makes finding evidence for distinction difficultCharacteristics of episodic and semantic memoryBut what about important autobiographical events?The first time I - semantic or episodic? Episodic Memory:Reference is to oneselfOrganised temporallyEvents remembered consciouslySusceptible to forgettingContext dependent Semantic Memory:Reference is with respect to general knowledgeNot organised temporallyEvents are knownRelatively permanentContext independentEpisodic / Semantic DistinctionPersonal semantics42Episodic - Semantic Distinction: ForgettingEpisodic memory is more prone to forgettingHowever, certain episodic events also appear very resistant to forgetting - Autobiographical first-time events Dramatic, emotionally arousing events which lead to flash-bulb memoriesSome semantic memory has been described asPermastore40% of Spanish vocab learned at school is retained 50 years later (Bahrick, 1984)There is still controversy surrounding whether there is anything special about flash-bulb memories.Forgetting43Episodic - Semantic Distinction: Neuropsychological dataAmnesic patients have intact conversational skills and perform normally on intelligence tests (which assess knowledge).But - cannot remember doing either five minutes later.

So: episodic, not semantic memory is impaired in amnesia?

Not necessarily - IQ tests and language acquired before onset of amnesia - not comparing like with like.

So: amnesia = impairment to acquire new information (both episodic and semantic?)Gabrieli et al, 1983: Trained HM with meanings of new popular words. Showed very little learning

More recently, when provided with extensive phonological cues (e.g Margaret Tha. - HM was able to produce names for 18 / 36 famous faces.Neuropsychological DataThe role of the mid-temporal lobe (MTL) in memory44Familiarity and recollection45 (familiarity) (recollection, source memory, relational memory). - -MTL :One-process theories -MTL .-MTL Two-process theories: -MTL : . . -perirhinal cortex .

The role of MTL structures in recognitionDuring encoding, representations of distinct items (e.g., people, objects, events) are formed in the perirhinal cortex and lateral entorhinal area. These representations along with back projections to the what pathways of the neocortex can then support subsequent judgments of familiarity. In addition, during encoding, item information is combined with contextual (where) representations that are formed in the parahippocampal cortex and medial entorhinal area, and the hippocampus associates items and their context (as first proposed by Mishkin et al. 1983). When an item is subsequently presented as a memory cue, the hippocampus completes the full pattern and mediates a recovery of the contextual representation in the parahippocampal cortex and medial entorhinal area. Hippocampal processing may also recover specific item associates of the cue and reactivate those representations in the perirhinal cortex and lateralentorhinal area. The recovery of context and item associations constitutes the experience of recollection.49

Frontotemporal DementiaDefinition: clinicopathologic condition consisting of deterioration of personality and cognition. It is associated with with prominent frontal and temporal lobe atrophyAccounts for up to 3-20% of dementias

PrevalenceMean age of onset 52.8 (Ratnavalli et al. Neurology 2002;58:1615-1621) Male preponderance 14:3 in one study and M=F in othersDementia prevalence of 81 per 100,000 (95% CI, 62.8 to 104.5) in the 45-64 year age groupPrevalence of AD and FTD in 45-64 age group same at 15 per 100,000 (8.4-27.0)

PathologyAtrophy may be associated with Picks bodies, nonspecific superficial cortical neuron loss.Prominent frontal and temporal lobar atrophy

Frontotemporal DementiaImpaired frontal lobe functions in absence of severe amnesia, aphasia, or visuo-spatial deficits

PathologyProminent frontal and temporal lobar atrophy (bilateral or unilateral).

Atrophy may be associated with Picks bodies, nonspecific superficial cortical neuron loss.

Characteristics of semantic memory disordrs56 - anterior temporal cortex . - :

( ) Characteristics of semantic memory disordrs57Dissociations between the frontal variant and temporal variant of fronto-temporal dementia:

The frontal patients are more deficient in understanding actions whereas the temporal variant patients are more deficient in understanding concepts

?58 ? - ? ?59Semantic Deficiencies/ Semantic Dementia Synonyms: Progressive fluent aphasia, Fronto-Temporal Demantia (tvFTD)Neuropathology: Non-alzheimer type degenerative pathology of the polar and inferolateral temporal cortex (relative sparing of hippocampus in early stages).

Symptoms: Progessive, selective deterioration in semantic memory, affecting verbal and nonverbal aspects of knowledge about objects, people, facts, concepts and word meanings.E.g. Patients response when shown a picture of a giraffeTime 1: A giraffeTime 2: A tall African animalTime 3: A horseTime 4: An animalTime 5: Dont know.

Episodic memory is relatively preserved (at least early in the course of the illness)59Easy to see why this hypothesis was developed:Amnesics can converse normally, and often speak knowledgably on pre-accident topics.60Episodic - Semantic Distinction: UpdateWheeler, Stuss & Tulving (1997) - reformulated the episodic / semantic distinction.

Placed a greater emphasis on distinction in terms of conscious experience.

Also argued that episodic memory (and the conscious act of remembering) is particularly dependent on cortical networks involving PFC.

Two lines of supporting evidence:1. neuropsychological evidence from patients with frontal lobe lesions.

2. Functional imaging data from PET / fMRI studies.Update61Episodic - Semantic Distinction: PFC lesionsPFC Lesions

PFC lesions usually result from: Head injury, NeurosurgeryAneurysm62Episodic - Semantic Distinction: PFC lesionsPFC lesions do not result in a full blown amnesic syndrome

In fact, until recently, memory was thought to be essentially intact in these patients

However, careful testing reveals interesting pattern of impairment.

In a meta-analysis of studies assessing free recall, cued recall and recognition in patient with frontal lobe lesions, 2 findings emerged:

1. Recall is more impaired than recognition (particularly when strategies can be used at encoding and/or retrieval2. Numerically, even recognition memory is poor, relative to controls.PFC Lesions63Episodic - Semantic Distinction: PFC lesionsWheeler, Stuss & Tulving (1995) argued that this pattern of results occurred because successful recall is more reliant on conscious recollection than successful recognition.

BUT: Both can be influenced by non-conscious memory.

Frontal lobe patients also have other interesting memory impairments-

Source Amnesia:

Patients can often remember the item / fact that was learned, but cannot remember where or how the information was acquired.PFC Lesions64Janowsky et al (1989): Asked FL patients and controls to remember a list of previously new facts (e.g. The name of the dog on the crackerjacks box is Bingo) and known facts.

~7 days later recall tested. Subjects asked about 20 old facts and 20 new facts.When Ss answered correctly, they were asked to recollect the source of the info How did you learn this fact? When was the last time you heard this fact?

Source Error = 1. Correctly recalling learned fact, but falsely reporting that it was last encountered before the learning trial 2. Correctly recall a new fact, but falsely reporting that it was learned during the learning trial.PFC and Source Amnesia65PFC and Source Amnesia

Result could be taken as evidence for dissociation between semantic (fact) and episodic (source) memory.However, current theories ascribe this result to a specific impairment in the ability to encode / retrieve contextual information66In 25/26 studies the right prefrontal cortex (PFC) was more active during retrieval of episodic information compared to retrieval of semantic information (Nyberg et al, 1996).

Hemispheric Encoding and Retrieval Asymmetry model (HERA)

In general, Left PFC involved in encoding, right PFC involved in retrieval.

BUT - it would appear that task difficulty and nature of encoded / retrieved material (e.g. verbal vs visual) might be more important.

ALSO - PET studies using subtraction methodology rely on several key assumptions that are particularly difficult to justify with respect to memory researchFunctional Neuroimaging67 Episodic / Semantic distinction is intuitively plausible:There is something phenomonologically different about remembering what you had for breakfast and the name of the worlds highest mountain However, there is little compelling evidence that the distinction reflects the operation of two completely distinct memory systems.The debate is still active, and the terms are widely used, just not necessarily in the way in which Tulving proposes Baddeley speculates that semantic memories result from an accumulation of similar episodic memories. They become knowledge when we are no longer able to retrieve individual learning episodesSummaryChart5253.7857142857339.4166666667341.8571428571

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