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35 Cards in this Set
- Front
- Back
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Broca’saphasia |
-Difficultyin production - Agrammatismu Effortful -Dysprosodicu Comprehensionis reasonable -Canwrite |
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n Wernicke’sAphasia |
-Fluent,prosodic, effortless -Fasterthan normal -Difficultyin comprehension -Make upnew words >>Neologismu -Canwriteu - Languageproduction is fine -Doesn’tmake sense (loss of semantic) |
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l Broca’sarea vs. Broca’s aphasia |
-Broca’sarea is left posterior inferior frontal gyrus -To getbroca’s aphasia, you have to have damages on insula, claustrum, putamen,anterior inferior parietal lobe and underlying white matter-internal, extermal,extreme capsules and superior longitudinal fascicles |
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Mohr, 1976 |
-Brocathought tat all of the extra damage was due to spreading of the stroke and he thereforetried to pinpoint the origin to the posterior IFG. -Blockageof the upper division of middle cerebral artery |
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wernicke's area |
-Thereis a connection between broca’s area and wernicke’s area (arcuate fasciculus(inner white matter)n Wernickethought that there was a short pathway running medial to the insula to connectthose two |
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l Thetraditional view |
-Geschwindis an aphasiologist who emphasized the importance of the arcuate fasciculus toconnect these area (first reading) |
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Whathappens if AF is damaged? |
n Conductionaphasia (disconnection syndrome)u Patientscan speak reasonably well:-some hesitation -some paraphasias: phonemic(spoon >> spook), verbal (spoon >> fork)u Comprehensionis normal - Can’trepeat - Geschwindhypothesized that patients can spontaneously speak and even paraphrase because Broca’s area and other cortical area are intact -Patientscould understand because Heschl’s gyrus and Wernicke’s area are intactu Repetitionword for word requires a tight connection between Wernicke’s area and Broca’sarea (arcuate fascicles) -Adifferent interpretationn - Warringtonand Shallice-London: conduction aphasia is actually a short term memory problemn It isdue to damage of the cortex of the Supermarginal gyrus that sits above thearcuate fascicle - Theinterpretation is that the SMG (40, PF) of the left hemisphere is important forphonological working memory - Connectsto frontal lobes through superior longitudinal fasciculus |
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l Problem |
-Botharcuate fasciulus and overlying grey matter should be damaged; lesion is large -Can’tuse animal models -Probablya combination of two theories -Geschwind(arcuate)u Warringtonand shallice (SMG-frontal through superior longitudinal) |
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l GeneralConclusion |
-Theentire peri-Sylvian region of the left hemisphere is the “language zone” -But allthe cortex is necessary for language – all of our concepts/memories/thoughtsare stored |
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l TranscorticalAphasia |
-Completelyopposite of conduction aphasian Girl inboston who tried to commit suicide using carbon monoxide >> most of cortex damage -Geschwindexamined brain and saw an isolation of the speech area -However,spontaneous speech was lost; No comprehension -Butcould repeat |
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l Apraxia |
-Liepmanndescribed apraxia as a higher level motor problem 1)ideomotor apraxia 2)ideationalapraxia |
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l Ideomotorapraxia |
-Failureto coordinate the muscle/limbs to create an action for communication (wavegoodbye/salute) - It is adisconnection between the idea and action -Damageto left supramarginal gyrus and underlying white matter |
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Geschwind’sinterpretation |
-(disconnectionsyndrome) -Geschwindtheorized that ideomotor apraxia is a disconnection syndrome (as he did withconduction aphasia) as patients can understand and can move normally. - Theproblem lies in going from understanding the command to carrying out the motion - Damageto left arcuate fasciculus will mean that the patient can understand thecommand and can move normally but cannot perform the command with either sideof the body. |
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l Geschwindand sympathetic apraxia |
-Is itpossible to have ideomotor apraxia on just one side of the body? -Somepatients have a 1) right hemiplegia (paralysis of right arm) and 2) ideomotorapraxia of the left side of the body. 3) broca’s aphasia or at least somespeech problems-since LMAC is damaged -This isknown as sympathetic apraxia -Suchpatients have damage to the left premotor and motor areas |
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l Thealternative explanation |
-Studiesof ideomotor apraxia show that many patients lose ability to use body tocommunicate even WITHOUT a verbal command (eg. Luria’s patient) -Additionally,we now have a much better understanding of what is going on in the parental lobes -Thealternative explanation for ideomotor apraxia is the importance of the left SMG(Brodmann area 40; area PF) for using the body to communicate |
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l Thesomatosensory cortex |
-Brodmannidentified 3 cytoarchitectonic area on the post-central gyrus -Kaasinvestigated these areas in the monkey. It turns out that each area has a map(homunculus) of the body and that the maps are mirror images of one another |
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l SomatosensoryCortex |
-Area3 :real S1 >> neurons have small receptive fields and respond to tactilestimulation of contralateral side of body (continuous response if continuousstimulation) -Area 1:receptive fields are bigger. Neurons seem to code vibrations of tactilestimulation (neurons respond when apply and remove stimulus) -Area 2:receptive fields are even bigger. Neurons seem to respond to fine changes injoint position |
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PosteriorParietal Cortex |
-All ofthis information is sent to the anterior SPL and IPL -Inthese areas, neurons don’t respond to tactile stimulation anymoren Rather,research by Sakata (monkey research) shows neurons here respond to extremelyspecific body movement (right hand to left shoulder). -Additionally,patients with damage to the parietal lobes lose their body schema -Touchyour noseu Whereis your right arm now -Examinerpoints to a drawing and says identify this body part on your own body -Patientswith damage in parietal lobes cannot do these things |
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imitation |
-Rizzolatti>>mirror neurons were found in anterior area 6. These neurons respond when amonkey carries out an action and ALSO when the monkey sees someone else do thesame action -Later,more mirror neurons were found in SMG -Then wefound direct connections between area 6 and SMG -Probablyan important network for interpreting one’s actions. Important forcommunication |
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l Conclusion |
-Ourgeneral understanding of the parietal lobes from discovering 1) Neuronsthat code for specific postures 2) The processing of the body schema 3) The presence of mirror neuronsIs thatthe parietal lobes integrate somatosensory information from the post-centralgyrus and visual information from the occipital lobes to code for movement ofthe body in space and to allow us to interact with our environment - In the lefthemisphere, the parietal lobe is probably important for doing these things tocommunicate -Hence,damage here could result in ideomotor apraxian Theproblem? Patients tend to have damage to both the cortex and underlying whitematter (eg. Arcuate fascicles) -Therefore,as with conduction aphasia, we can only postulate that the cortex is what isimportant! |
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l Writing |
-Usingbody to interact with object in the environment and use hand in a particularway to generate spatial squiggles that have linguistic meaning -Bodyinfo+spatial info+linguistics=writing (left parietal lobe) -Closerto postcenral gyrus than occipital SMG |
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l Ideationalapraxia |
-Leipmann:the programming of sequence of action using objects to execute an act -Example:a patient is asked to demonstrate how to prepare a letter to be mailed -Patientswith larger left parietal lesionscan understand the command, can name the objects. Still can’t perform the task.Wrong action with wrong objects |
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l Rightparietal lobe |
-Constructionalapraxia -Inabilityto reconstruct/create 2D or 3D model: eg. Build a tower with given blocks -Spatialneglect -Damageto right parietal lobe can cause hemi spatial neglect -Patientswill ignore the left side of the visual field and often the left side of theirbodies -Exampleof asking such a patient to draw a clock -This isNOT the same as left homonymous hemianopia |
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l Dominance |
1) Constructionalapraxia 2) Hemi-spatialneglect 3) Alexia, agraphia -We cansay that the right parietal lobe is more important for processingnon-linguistic spatial information -Theleft parietal lobe has evolved to be able to extract linguistic meaning fromsquiggles (reading) and reproduce these linguistic spatial relationship(writing). |
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l GerstmannSyndrome |
- Josefgerstamann used the following 4 symptoms to diagnose damage in the leftparietal lobe (before MRIs): 1) Fingeragnosia > inability to recognize one’s different fingers 2) Rightleft disorientation 3) Agraphia 4) Acalculia> math problem |
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VisualSystem |
l V1/area17 is the primary visual area since the early 20th centuryl Light getsreflected in retina and goes to specific part of thalamus and go to V1(striated cortex-calcarine sulcus) and V2, V3 and so onl Threevisual area (BA 17, 18, 19) within the occipital lobes. Visual processing stopsherel Wernicke’s(19th) and other knew about the importance of the STG in auditoryprocessing (Heschl’s gyrus)l Withpatient HM, we came to learn about the importance of the parahippocampal gyrusand memory consolidation |
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Ventraltemporal |
l akainferotemporal gyrus aka Silent cortexn Becausewhen you stimulate here, nothing happens >>> silent cortexn Whenyou stimulate postcentral gyrus, you will feel weird sensation |
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l Inferotemporalcortex |
n Mishkin,student of Hebb, decided to investigate the functions of this area in the 1960sn Heremoved the inferotemporal cortex bilaterally in monkeys and tested them onvisual discrimination tastn Themonkeys were not able to performn Thiswas the first link between the inferotemporal cortex and visual processingn Thesemonkeys could still learn auditory and tactile discrimination tasksn Thismeant motivation, attention, reward feedback learning was all functioningn Sothese lesions clearly affected the visual modality specificallyn Thiswas one of the most important scientific discoveries in the 20thcentury: this was the first time that one could associate the temporal lobeswith visual processing |
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l Hubeland Wiesel |
n Single-cellrecordings in alert monekys and cats to provide the first real insight into thefunctional organization of the occipital lobesn Won thenobel prize with sperryn Foundthat neurons respond to light in a certain part of the visual field – definedthis as the receptive field of the neuron: the part of the visual field (andtherefore the retina) where light needs to fall to activate the neuronn Receptivefields of neurons within the early visual stages are contralateral andretinotopically organized: move your eyes and that neuron cannot be activatedbecause you have changed where the light falls on the retina |
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l Receptivefield |
n Withinretina and LGN : respond to spots of light |
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l Hierarchyof organization |
n Hubeland Wiesel discoveredn V1/area17 neurons respond to bars and edges of light in particular orientations. Stillcontralateral VF, retinotopic organizationn Also,these neurons in V1 are organized into ocular dominance columns and orientationcolumnsn V2 isBA 18. Respond to more complex stimuli. Still retinotopicn V3 andV4 are area 19. There are upto V6Inother words, as we move more anteriorly, receptive fields get larger andneurons respond to more complex stimuli |
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l Visualprocessing |
n As moveanteriorly, the stimulus needed to elicit a response becomes more complex. Thereis a convergence of information from lower visual areas to higher onesn Receptivefields get larger and largern By thetime reach the anterior IT cortex, the neurons respond to individual objects nomatter where placed in visual field |
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l Ventralstream: object recognition |
n Singleneuron recordings in anterior IT cortex of monkeys have demonstrated responsesto specific objectsn Faceselective neurons have also been found, specifically in the fusiform gyrusn Notreceived well in the scientific community… continues to be an on-going debate |
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l Thegrandmother cell hypothesis |
n Thesparse coding theory: individual neurons code for specific objects in theenvironmentn Quirogaand Connor articles (coursepack) discuss evidence for sparse coding:u Rocrdedin the medial temporal lobesu Recorededin patients before they underwent surgeryu Found aneuron that responded to Jennifer Aniston and nothing elseu Foundother neurons that were specific to other objectsu Additionally,work by Tanaka has suggested that one can alter the features of the object andstill get a response |
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l Cellassemblies |
n Hebb:The Organization of Behaviour (1949) >> stressed the idea of cellassemblies, group firing (“Neurons that fire together wire together”)n So,there probably no “grandmother cell” but rather a complex cell assembly thatneeds to be activated to code a specific object. Population codingn Similarobjects activate a percentage of that object’s cell assembly (Dr. Petrides andhis brother) because of some of the same features |
