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Cognitive Neuroscience

by: Watson Stamm Jr.

Cognitive Neuroscience PSYC 685

Marketplace > George Mason University > Psychlogy > PSYC 685 > Cognitive Neuroscience
Watson Stamm Jr.
GPA 3.54

Raja Parasuraman

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Raja Parasuraman
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This 115 page Class Notes was uploaded by Watson Stamm Jr. on Monday September 28, 2015. The Class Notes belongs to PSYC 685 at George Mason University taught by Raja Parasuraman in Fall. Since its upload, it has received 44 views. For similar materials see /class/215171/psyc-685-george-mason-university in Psychlogy at George Mason University.


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Date Created: 09/28/15
Cognitive Neuroscience PSYC 685 The Future of Cognitive Neuroscience a Raja Paras uraman Current Cog Neuro Methods Neuroimaging Electrophysiology Cognitive Testing Computational Modeling Molecular Genetics Neuroimaging Alphabet Soup EEG Electroencephalography 19305 ERPs EventRelated Potentials 19605 CT Computed Tomography 19805 MEG Magnetoencephalography 19805 MRI Magnetic Resonance Imaging 19805 PET Positron Emission Tomography 19805 SPECT Single Photon Emission Computed Tomography 19905 3 fMRI Functional Magnetic Resonance Imaging 19905 TCDS Transcranial Doppler Sonography 19905 NIRS Near Infrared Spectroscopy 19905 TMS Transcranial Magnetic Stimulation 19905 fNIRS Fast Near Infrared Spectroscopy 20005 Current Developments in Neuroimaging Higher strength fMRI 7 7 Tesla already in place 7 12 Tesla 2 in the world NIH and Oregon 7 Is bigger better 7 Limit set by size of cortical column microns and vascular size Future Developments in Neuroimaging 0 Portable fMRI Atomic Magnetometer Does not need high supercooled magnetic eld Weight and interference issues n mm f Shh vbgnemmem pun slagmania I 39 L can om qu 39 magmas PIE mini x can E I1 D Scum mm m M12 np I39m NmSwIprl 2 Current Developments in Molecular Genetics 0 Complete coding of human genome SNP databases 3 million 0 Associate SNPs with variations in cognitive function Visuospatial attention Executive attention Working memory Episodic memory The APOE Gene 19q132 chromosome 19 550 kb promoter area 3 i 2 l start codon stop codon 3Drendering of the apolipoprotein E4 isoform polymorphisms rs429358 C3737 gt T and rs7412 C4075 gt T CGC codons starting at residues 3739 and 4075 yield Arg whereas TCG codons yield Cys Arg 158 Cys for E2 and Arg E3 Arg 112 Cys for E2 and E3 The CHRNA4 Gene 20q132 q133 chromosome 20 I u I ll I I 1629 kb I I I I I I I I I I I I I I I I I 39 promoter H I u H I I start T1545C variation stop rs1044396 Future Developments in Molecular Genetics Complete coding of human proteome Proteomic databases Associate proteins with Variations in cognition o 7 Subtmtive genomics Highly speci c gene expression patterns 7 e g single CA iield in hippocampus Future NeuroTechnologies 0 Brain implants cortical vision hippocampal memory boosters parietal cortex implants for neglect 0 Brain chips Cochlear implants Memory storage chips More Technologies Cognitive and Affective Enhancement of Normal Function BrainMind Reading fMRI NIRs BrainComputer Interfaces Neural Engineering siliconneuron 247 Neurobehavioral Monitoring Cyborgs Cognitive Neuroscience PSYC 685 Visual Attention Raja Parasuraman Overview Varieties of attention Early vs late selection Spatial selection The frontoparietal attention system Neglect William James on Attention Every one knows what attention is Itis the taking possession by the mind in clear and vivid form of one out of what seem several simultaneously possible objects or trains of th ought F ocalization concentration of consciousna39s are of its msence It implies withdrawal from some things in order to deal effectively with others and is a condition which has a real opposite in the confused dazed scatterbrained state which in French is called distraction and Z erstreutheit in German Varieties of Attention William James 1890 The Principles of Psychology Chapter XI Attention Section Heading The Varieties of Attention Posner amp Boies 1971 Components of attention Psychological Review Parasuraman amp Davies 1984 Varieties of Attention Academic Press Varieties of Attention 0 Selection 0 Vigilance 0 Executive Control Slide 5 Why is Selection Needed 0 Limited informationprocessing capacity of brain to cope with all sensory input eg 107 bits per second on retina 0 Hence Preferential processing of stimulus sources and features relevant to current goal attended selected Limited or no processing of irrelevant sources and features unattended unselected Slide 6 Why is Selection Needed 0 Even if processing capacity was not limited complete parallel processing of all sources of information may not be as ef cient as combined serialparallel processing 0 Biological Vision parallel processing pathways dorsal ventral cortical streams after V1 for different Visual features with serial processing of conjunctions of features feature binding 0 Arti cial Vision serial attentional window corresponding to one object or one location in Visual eld with parallel processing within location or object computationally more ef cient than full parallel processing of entire Visual eld Slide 7 Selective Attention The Gateway to Memory and Cognition Working Encoding Storage Memory Retrieval gt Implicit Learning Slide 8 Early vs Late Selection Theories of Attention 39 Cherry s 1953 cocktail party experiments 7 Listening to speech with one or two ears 7 When forced to attend to one ear shadowing little remembered of input to other ear 0 Broadhent 1954 similar experiments with different frequency tones presented to each ear 7 Can discriminate small changes intensity or duration in attended ear 7 Poor discrimination and nienmiy of changes in unattended ear Early vs Late Selection Theories of Attention Broadbent 1958 proposed the earlyselection model 7 irrelevant stimuli are ltered or gated at an early stage of information processing 7 before full identi cation and semantic analysis Treisman 1964 proposed an attenuation theory 7 irrelevant inputs are not completely gated but attenuated 7 highpriority but unattended inputs eg own name biologicallyrelevant stimuli can bleak through the lter Early vs Late Selection Theories of Attention Deutsch and Deutsch 1963 and Norman 1968 proposed the lateselection theory 7 All stimuli relevant or irrelevant are processed to the level of semantic ana ysis 7 Only attended stimulus is selected in the response selection and execution stage 7 In this model the meaning of unattended stimuli can be extracted Models of Selective Attention 1 s2 Attenuation SA Filter 0r Gate 1 Filter 0r Gate Current Models Variable Locus Filter 0r Gate 0 Both early and late selection are possible depending on stimulus and task demands 0 Lavie s 1995 Perceptual load theory Locus of selection is early When perceptual load is high many targets and distracters high stimulation rate etc How is Selection Implemented Location Spacebased selective attention 0 Features 7 Color Objects Objectbased selective attention j The Importance of Spatial 5 Selection 1 39 v v V pv While there is evidence for location feature and objectbased selection I I much evidence points to the primacy of locationbased selection A v v v V How is Spatial Selection Implemented Eye Iead Movements Spatial SBIBCtion Covert Spatial Attention Varying Focus of Attention or Spatial Scaling Zoom in and Zoom Out Each selection method can be 0 bottomup re exive topdown voluntary Slide 16 Covert Spatial Attention 0 Helmholtz s experiments 1894 0 Letters projected on wall with newly invented optical projection system 0 Electrical sparking of shutter to create brief 50 ms exposure 0 While xating on one spot Helmholtz coul identify letters some distance away from H xation Covert Spatial Attention Posner 1980 Developed simple spatial cuing or orienting task 7 Central xation 7 Left or right visual eld location cued peripheral cue re exive orienting 0 central arrow cue voluntary orienting 7 Cues are 0 valid 0 invalid 0 neutral Spatial Attention Letter Discrimination TaskPeripheral Cue Re exive or Involuntary Attention Shifting l l l Fixation A 1000 ms Cue 200 500 or 2000 ms Target 2000 ms Consonant or Vowel Slide 19 Spatial Attention Letter Discrimination TaskCentral Cue Voluntary Attention Shifting l gt Fixation A 1000 ms Cue 200 500 or 2000 ms Target 2000 ms Consonant or Vowel Slide 20 Reaction Time msec Effects of Covert Shifts of Attention on Letter Discrimination 500 39 450 39 400 39 03 01 O I 300 Cost Valid Neutral Invalid Location Cue The Attentional Spotlight 39 The spotlight moves from xation to a cued location 0 Facilitates sensory and perceptual processing of stimulus at cued location on Valid trials shorter RT increased accuracy 0 Invalid trials result in longer RT and reduced accuracy because the attentional spotlight has to moved to the uncued location 7 target Brain Areas Involved in Attention Posner amp Petersen 1990 r anla aye Amie cinema Involved in u Spatial Attention Neuroimaging of Selective Attention 0 Increased activation in cortical processing areas associated with perception of feature 0 Increased activation of posterior parietal cortex as well as frontal cortex during spatial attention Neuroimaging of Selective Attention 0 Source of attention control signals parietal cortex 0 Target of attention control signals perceptual processing areas eg area V4 for color Neuroimaging of Selective Attention 39 Corbetta et al 1990 PET study of selective attention to Color Form Motion 0 Selective condition compared to passive viewing or divided attention detect targets With any of the three features 0 After subtraction greater attentionrelated activation noted in cortical areas corresponding precisely to the perceptual processing areas Color Lingual gryus in occipital cortex Shape Fusiform gyrus in occipitotemporal cortex Motion Inferior parietal lobe Matchto sample task Match identity or color of faces to sample Selective Attention to Color and Face Identity Clark amp Parasuraman 1997 409 305 Js 305 605 tieral irtex Julugl Attention to ce identify activated flusiform gyrus ofFQWQcipitotemporal cortex RetinotODV of Visual Attention What Does Selective Attention Do 0 Increase activation of attended stimulus Gain control 0 Decrease activation of distractor stimulus Noise suppression 0 Increase prestimulus activation of cortical area subserving processing of to beattended stimulus Baseline preparatory activation 0 Reduce activation of competing stimuli Biased competion What Does Selective Attention Do 0 MRI evidence for 4 effects Gain control Corbetta et al 2000 Noise suppression Rees et al 1999 Baseline preparatory activation Kastner et al 2000 Biased competion Kastner et al 2000 0 Thus fMRI goes beyond localization to providing evidence relevant to theoretical mechanisms for selective attention in the brain Selective Attention to Targets Among Distractors 39 Posner orienting task requires only detection of a stimulus in an otherwise empty visual eld 0 Most realworld tasks involve detecting a target among distractors 0 Visual search task Treisman Conjunction search target de ned by conjunction of two or more features Feature search target de ned uniquely by single feature 0 IO i TargetR ed square o L A o I A Treisman s Feature Integration Theory 0 Feature search involves little or no use of spatial attention target pops out 0 Conjunction search involves a serial spatial attention shifting mechanism 4 Reaction Time Display set size Cueing in Visual Search Tasks 0 Zoom lens model Eriksen amp Yeh 1985 Focus of attention can be eXpanded zoom out covering greater area but at lower resolution or narrowed zoom in covering smaller area at higher resolution 0 Attentional scaling model Parasuraman amp Greenwood 1995 Precede Visual search array with cues of different size RT to nd target decreases with decreased cue more precise size Topdown Selection Search for a red square A Cued Visual Search Task Search array Task Search for a Pink N r Cue 500 msec Reaction Time msec 600 500 400 300 Large Imprecise Cue Small Precise Cue Area of Visual Field Cued degrees Reaction Time msec 600 500 400 300 Spatial Scaling of Attention Large Zoom Out Slope Dynamic Scaling of Spatial Attention Small Zoom In 0 1 2 3 4 5 6 Area of Visual Field Cued degrees Mechanisms of Spatial Selection 39 Eye movements overt orienting 0 Attentional spotlight covert orienting 0 Varying focus of attention attentional scaling 0 All 3 mechanisms can be bottomup stimulusdriven involuntary or topdown knowledgedriven voluntary 0 Evidence suggests that a common frontoparietal cortical network is involved in all 3 mechanisms although there may Withinnetwork differences and the localization of attentional scaling is not as well understood Activation of neuron in parietal cortex during attention to a visual stimulus L mntvrmtlng largct m argu l t i 1 Targd presented Di i ii neuronal activity over IS l39illlS 5mm u nvuruunl Il 39ll39 41 average 3 neuronal 5 activity ti 1 a Time s D iu l i 0 0H ERPs to attended and unattended Visual stimuli Computational Model of Spatial Attention Koch amp Ullman 1985 39 Visual features analyzed in separate spatial maps as in Treisman s 1980 model color orientation motion Etc 0 Spatial competition Within each feature map to determine most salient location 0 A combined saliency map is made from all the parallel feature maps 0 The combined saliency map is scanned by attention this step is serial and rate limited by the movement of spatial attention colam use gveen mm mm am nmbman 01 return wmnm u 1 Computational Implementation of a WinnerTakeAll Network 0 Assume n elements in the saliency map need to nd the most salient location on the map 0 Fully parallel The fastest method is comparison of all n nodes through massively parallel connections takes t 1 time step but requires 112 11 connections and is biologically implausible Computational Implementation of a WinnerTakeAll Network 0 Fully serial The slowest method is serial comparison by pairs takes t n 1 time steps too slow 0 Computationally ef cient biological plausible compromise compare m elements in parallel m2 m connections Where n gtgt m takes t logmn time steps Ifn8and m2thentime3 If n 256 and m 2 then time 8 If n 10000 and m 10 then time 4 ObjectBased Attention Kanwisher 2000 Faces and houses transparently superimposed on each other and cycled rapidly along one of four axes 0 Both objects occupy same location hence locationbased selection not possible Participants asked to attend to either face house or direction of axismotion ObjectBased Attention Activation in fusiform gyrus face area greater during attention to faces featurebased attention Activation of middle temporal gyrus motion area greater during attention to motion featurebased attention Greater activation of area MT during face attention When face moved same object than When house moved object based attention Neglect 0 Patient does not attend to stimulus in Visual eld that is contralateral to site of brain lesion 0 Not a sensory loss patient can see and detect stimuli in neglected eld When pointed out Not a motor loss patient can point to or touch or move eyes to stimulus in neglected eld LVF RVF Neglected eld Neglect Typically found after unilateral damage due to stroke eg middle cerebral artery occlusion More typical after right hemisphere lesion Often involves lesion of posterior parietal cortex Testing of Contralateral Neglect Syndrome patient ignores and does not copy left side of drawing MOM Patients copy Model Pationt39s mpv Even when asked to draw an object from memory with eyes closed they draw only the right side Cognitive Neuroscience PSYC 685 Learning and Memory Raja Paras uraman Overview Short term working and longterm memory The medial temporal lobeprefrontal cortex memory system Amnesia Implicit memory Slide 2 De nitions 0 Learning the process of acquiring new information or new behaviors 0 Memory Persistence of learning that can be revealed at a later time 0 Learning gt Memory 0 Learning and memory can be both explicit and implicit Slide 3 Attention and Memory Working Memory Explicit Memory recall recognition Implicit Memory enhanced performance Slide 4 Memory Structures 0 Sensory memory Iconic memory vision Echoic memory audition Shortterm memory 0 Longterm memory Slide 5 Taxonomy of Memory MEMORY Slide 6 Memory Processes 0 Encoding Acquisition Consolidation 0 RehearsalStorage Rote rehearsal Elaborative rehearsal 0 Retrieval Slide 7 Memory Outcomes Sensory memory Shortterm memory Longterm memory Encoding X RehearsalStorage Retrieval Recall Recognition quot a Slide 8 Sensory Memory Very Short Term Memory 39 Sperling s partial report method 7 Iconic memory Vision F c H D 7 Echoic memory audition J R P 0 0 Standard whole report technique 34 D N B A letters underestimates capacity of sensory memory because of its short duration high tone 0 Partial report technique requires unpredictable report of subset of items 38 low tone letters per row thus capacity 3 X 38 114 letters close to perfect Slide 9 Sensory Memory 0 Capacity Very high Iconic memory 0 Duration Very short 0 Capacity X duration tradeoff 0 Vision 05 1 second 0 Audition 410 seconds 0 Mismatch negativity ERP supports long estimates for echoic memory 2 4 6 8 10 Time sec Slide 10 Shortterm Memory 0 Ebbinghaus 1880 forgetting curves 0 Memory for nonsense syllables eg PZK to reduce effects of semantic memory Ebhinghaus s Forgetting Curve Immediate recall 20 minutes of syllables remembered l 2 s 3 Days since learning Slide ll Shortterm Memory 39 Most people can hold about 7 items in shortterm memory 7 Phone number with access and area code 77313016677891 7 Zip code 220304441 3915 forgetting due to 7 memory decay 7 interference from new material Delay x Petersen amp Petersen s 1959 Studies of Shortterm Memory 0 Recall nonsense syllables eg XJ C while doing secondary task backwards counting during retention interval eliminates interference from new items and prevents rehearsal Test for recall at varying times following initial presentation 0 Accuracy of recall falls with time Slide 13 Capacity of STM Miller s Magic Number 72 items 7 letters 7 wor ds 7 objects 7 numbers 0 General limit of STM capacity 0 However more recent estimates suggest smaller limit 4 items Slide 14 Chunking 0 What is a unit in STM 0 Of two sets of items FBIIRSGMUMIT IMUSRMGTIBIF 0 the rst is easier to retain in STM because it can be parsed into 4 chunks FBI IRS GMU MIT Slide 15 Chunks and SuperChunks Chunks Govt Agencies Universities 2 FBI IRS GMU MIT 4 FBIIRSGMUMIT 12 0 Using this procedure Ericsson amp Chase 1973 showed that long distance runners could increase memory capacity to 100 s of unrelated numbers slide 16 Percent Correct Serial Position Curve Primacy LTM e g eliminated by fast presentation Recency S TM eg eliminated by distracting task 10 Item p0s1t10n number Slide 17 Model of ShortTerm and LongTerm Memory Atkinson amp Shiffrin 1968 The Modal Model rehearsal Encoded Shortterm Longterm input memory memory 39 l I V STM decay Permanent storage Slide 18 Comparisons of Memory Structures Conscious Capacity Duration Code Awareness 9 Sensory Memory Very high Very short Physical No Veridical STM 47 chunks Short Acoustic Yes seconds to Visuospatial minutes LTM Potentially Very long Semantic Potentially unlimited minutes to Yes days to Slide 19 years Working Memory Revision of the Modal Model of STM 0 Modal model suggests that STM is the gateway for LTM 0 Evidence against the model Warrington amp Shallice 1969 reported on an amnesic patient who had very short digit span 2 items but could form new LTMs Markowitz et al 1999 amnesic patient with STM de cit but no LTM problem Patient HM with bilateral temporal lobe lesion has normal STM but impaired at forming new LTMs Hence double dissociation between STM and LTM de cits Slide 20 Working Memory Baddeley amp Hitch 1974 model 7 Limited capacity store for both retaining information and performing mental operations on working the stor ed infor mation Phonological auditory loop Visuospatial skemhpad Cemml execu ve Lesioning Working Memory 0 Phonological loop Lateral inferior frontal gyrus Poor WM for words but NO speech or language de cits Visuospatial Sketchpad Parietooccipital sulcus R hem gt L hem Poor WM for nonverbal visual stimuli eg blocks but otherwise no visual de cits pmmml mum uhuln 5mm pmcu ory r wlunary Lplnaal Mrnlnrmmalu hypumnlnmus Pamhlywcimmla Slide 22 Long Term Memory 0 Declarative Explicit Memory Episodic memory 0 speci c events 0 speci c times and places Semantic memory 0 facts 0 general and speci c knowledge 0 Nondeclarative Implicit Memory Procedural memory Priming Classical conditioning Slide 23 Neuroimaging of Episodic Memory FIG 1 perteption items witli unfamiiar faces preventing covert to most ottlie areas demonstrating activations relative In tl rehearsal of the face memories perception control task Table 2 The overlap between are PET Scannin tPETscallswereohtainedwilh aScandiuonix demonstrating activation relative to tne perception and se model 2048158 scannei Scandinant Milwaukee using sorimolor control tasks was incom lele in three localioi metiiods described clscwhere 20 Ea li taalt b gan 1 mi Relative to the sensorinrotor conuul the left romal an c beforesthe intravenous injection of37S incl 1 0 376 associated with encoding did not include the midtrontal r of Hz 0 rCBFvalues in nni i 39 39 t i I 39 associated wi p Sth mm mq iax l ri i ngmm o eEntencrsectcranatien Statistical Analysist Data were 39 i 39 39 39a niionwas not parametric mapping and m memm mmd r rCBF H tasks f quot39 70 og t of suf cic W mr eminence volume e C 75 39 t cmquot 39 was assessed based on their spatial extent 25 an extensive hilaleial region of perisylvian and postcenti TWO sets of comparisons were made lo idenlify th brain cortex in addilion in all of the areas demonstrating decxeas in am mg m t mmma n ma n t m Wm mt m cm W quotor Neuroimaging of Episodic Memory 0 Face perception and recognition study with PET Habe et al 1996 0 Right hippocampus activated during encoding gt perception but not during recognition 0 Right prefrontal cortex activated during recognition but not encoding Slide 25 Habe et al PET 1996 study Neuroimaging of Episodic Memory 0 Eventrelated MRI studies of individual item episodic memory Wagner et al 1998 0 MRI activation associated with encoding of single words compared to later next day recognition memory for words 0 Greater activation in parahippocampal and prefrontal regions for remembered than for forgotten words Slide 27 Neuroimaging of Episodic Memory Hippocampal and left frontal activation during encoding predicts subsequent successful episodic memory 0 Right prefrontal cortex activated during recognition but not encoding 0 Con rmed by metaanalysis of 275 PET and fMRI studies Cabeza amp Nyberg 2000 Slide 28 Hebb 1949 on shortterm and longterm memory A I t 39 The Organization of Behavior When an axon of cell A is near enough to excite cell B and repeatedly or n 1 persistently takes part in firing it some growth process or metabolic change takes place in one or both cells such thatA s efficiency as one of the cells firing B is increased Cell assembly theory STM activation of neural cell assembly for short period of time without external input LTM structural change in synapses between neurons in the assembly Slide 29 Cell Assembly Theory 0 Closed loops become functionally associated With repeated coexcitation 0 Assembly initially organized by stimulus input but subsequently reverberates in the absence of inputSTM 0 Period of no new input is required for LTM formation consolidation 15 min Afferent axon F C gt A D gt gt B E fferent axons 0 E C Cell assembly A B C Slide 30 Reverberating cell assembly Numbers refer to order in which neurons re suds 31 Cell Assembly Theory 0 If assembly is not disturbed during consolidation structural change occurs LTM Cell assembly can be activated by other cell assemblies associative memory Collective reactivation of different cell assemblies recall thinking Slide 32 Hebbian Learning 5 5116233 Validation and Application of Hebb s 1949 Theoretical Predictions 0 Hebbian learning Longterm potentiation LTP in hippocampus 1973 Learning rule in connectionist networks 1986 0 Reverberation in cell assembly as basis for short term memory Coherence changes in EEG between cortical areas 1985 0 Structural change as basis for LTM Synaptic growth following learning 1985 Slide 34 Associative Network Models of Memory oAssociative neural networks can store memories 0 Hop eld network is a speci c example of an auto associative network unsupervised learning 0 Modeling the hippocampus Mainsuhsuucluxes Emnrhiml annex Dendale gyms CA tenmu Ammonisi iam s humquot xeg39nns cm and CA3 rennmn path ennmimi annex aenme gylus cm ennmimi annex Slide 35 Associative Network Models of Memory oModeling the hippocampus CA3 region receives inputs from many regions of association cortex via entorhinal cortex and dentate gyrus the perforant pathway 16000 synapses in a typical CA3 neuron About 11000 of these synapses are inputs from other CA3 neurons CA3 neurons may thus constitute an a recurrent autoassociative matrix Hop eld network CA3 neurons autoassociate different sensory features of an event into a single episodic memory CA1 neurons return activated episode for storage in sensoryspeci c cortex Slide 36 Anatomy of the Hippocampus m 1 suds 37 Amnesia 0 De nition Memory loss for old information and events inability to learn new information or both 0 Retrograde amnesia for information prior to brain lesion or brain injury 0 Anterograde amnesia for information after brain insult Slide 38 Causes of Amnesia 0 Speci c brain lesions medial temporal lobe hippocampus diencephalon dorsal thalamus prefrontal cortex Generalized brain insult eg closedhead injury 0 Electroconvulsive therapy even with unilateral ECT 0 Korsakoff s syndrome thiamine de ciency associated with alcoholism diencephalic and diffuse cortical atrophy Slide 39 Hippocampal atrophy in Alzheimer s disease 39 Severe memory loss in AD over and above that due to normal aging nipN w 341 74 Mae3w yuan Progresslve worsenmg of memory loss over time Norma Elderly Alzheimer39s Disease 0 Progressive decrease in hippocampal volume in AD mnunnamnus suds AU HM 39 Bilateral removal of medial temporal lobe for control of intractable epilepsy 0 After surgery showed normal sensory and working memory 0 Normal intelligence and good memory for events prior to surgery no retrograde amnesia 0 But inability to form new LTMs 7 forgets a persorr he has been imroduoed to 5 mmules ago 7 will not remember a psychological task shown to him a few hours Ora day ago but r r will perform better at it good pmceduml or implicit memorysee ter Sllde Al HM OMRI done when metal clips in brain were found not to be magnetic 0 Con rmed lesion of anterior hippocampus but showed intact posterior hippocampus However atrophy may have led to little or no hippocampal function 0 HM is in his 70s today still remembers major events of the 1950s but can learn through association some new facts 0 Continues to help the study of memory by participating in cognitive neuroscience research 0 New patients are available but few have bilateral hippocampal lesions Slide 42 Unilateral Hipppocampal Lesions Materialspeci c de cits in learning new items 0 Left hippocampus Nonsense syllables Digit span Word recall Right hippocampus Face recognition Spatial memory Spatial block span Slide 43 Consolidation 0 How LTM develops after initial acquisition prior to permanent LTM trace 0 Can take hours days months 0 Newly presented items can interfere with learning of older items if presented in close temporal proximity to the older items Slide 44 Consolidation 0 Loss of consciousness due to head injury can produce brief retrograde amnesia Electroconvulsive therapy ECT produces most longlasting retrograde amnesia Retrograde amnesia Recovery Low Time of brain insult Memory strength Time Slide 45 Consolidation 0 The hippocampus is thought to be involved in both encoding of tobelearned information and the consolidation process 0 Once consolidation is over hippocampal involvement not required 0 LTM trace is NOT stored in hippocampus but in corresponding cortical association areas Slide 46 HM in Fiction Memento Opening lines Sn where are yuu Yuu39ne in same mutelruum Yuu iust yuu justwake up and yuu39ne in in a mulel ruum There39s the key ItfeeLs like maybe it39s just thefirst time yuu39ve been there butperhaps yuu39ve been therefara week three munths It39s it39s kind ufhard ta say I dun39t I dun39t knuw It39s just an anunymuus m suds A7 Implicit Memory 0 A form of memory in which learning is demonstrated by more ef cient performance during subsequent exposure to an itemfaster reaction time fewer errors fewer trials to learn etc but 0 NOT by explicit recall or recognition 0 Can be dissociated from awareness Slide 48 Implicit Memory Tests 0 Wordstem completion Shown word QUEEN Subsequently asked to generate rst word that comes to mind with the stem QU Amnesic patients generate Queen more often than equally familiar or frequent possibilities such as Quick Have no explicit memory for Queen Slide 49 Implicit Memory Tests 0 Serial Reaction Time Task 4 stimulus lights 4 response keys Stimulus sequences repeated eg 143223M314M3113 or totally random Normal subjects show reduced reaction time to repeated sequence and some proportion report being aware of the repeated patterns HM and other amnesic patients also showed reduced RT but have no explicit awareness of the pattern Slide 50


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