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PSY493 OCT 30.docx

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Adam Keith Anderson

PSY493 OCT 30, 2012 Overview - Two pathways what and where - Ventral and dorsal resp - Parvo becomes over represented in the brain more layers in the - Know by conscious experience devoted to colour vision, the fovea over represented in the system - And become the what pathway and the ventral patway down to ventral surface of the visual system - Two object recognition - Last time analysis by parts and analysis of whole two stargeties ventral uses - And dorsal pathway classic non human work where pathway and revised work at western how this part is for action the origin of this pathway is magno from periphery - Good for action or how to localize things in environment Computational - How solve problems without knowing how and they seem trivial to recoginize objects - Reason difficult problem of object constancy - In morning leave your and see it on perspective and come different vanatae point and different perspective things to retina look nothing alike and no problem understanding and try to be naïve perceiver they look nothing like each other - Brain has to do same visual rep not same on retina is same thing - Occlusion behind a pole you don see it cut in two but a computer would and perception continues acroos this region to know it is one object - Non conical – position not used to seeing it – non typical perspective and visual system must adjust - Read in the moringin lots of white light present waveleneghts in the blue wv spectrum and in sundown ambeient light is yellow ev is in green yellow range - perceiving what is on the reina wouldn’t see blue - Not even using wv on retina taking in all the ambient light Wheres waldo - Other problem first is what is it and second is where is it - Our perception of it is always in a location - Perceive it in location separate problem brain has to solve - Distinct problem brain has to solve - In perception location and object are together but problem brain has to solve what is it and where it is - Visual system sovles where it is - Classic problem of finding waldo – - Cetain features find what is waldo and then where Two pathways - Start of in differentiation in retina and two pathways in brain - What and where and reflected in division of labour - Inferior axons collect – thick cord of axons – ilf what it is - Magno bundled together action where - Two big highways from v1 all traffic together lots of congestion and two major roads Dissociation - Data from the study - Rhesus subjected to lesions - Landmark task and object discrimation - Monley where is raisin is – at location of object - Tells you where to find the reward - Par dorsal and temp ventral - And unoperated control - X axis is different trials over time where it is located left and right continuous challenging - All animals initial difficulty - Green almost perfect - Parietal continue to have deficit even with practive - Temp – disociaition – leaves this ability intact - What is similar to unoperated - Suggest dorsal pathway is - Double dissociation - This one is single on type of legion causes deficit and another doesn’t - Why need double - Difficult may do many other things - Not difficulty - Temp lobe lesion can result in deficit – only showed its not involed in something want to show it is involeved in something - Disc not where learning is food next to cube another may be cylinder learning where to find food on object identification - Animals can disc following temp legion disc deficit - Deficit is to distinguish between cylinder and cube - I can reco object as cup but not know where it is - See cup wouldn’t know where it is? What - Most anterior potions and the front v1 occ lobe - Down ventral pathway to tips or poles - Region and looking at receptive field properties there different from back - Receptive fields arevery small lonely see little bit of world - Move down rec field go bigger and bigger - Tip contaisn most of the hemifield Next - Not size but types of features that cause them to respond - Anterior finding intersiting selectivity for many objects - From hand to mit –subjective impression stripping fine detailes neural response goes down - Hand different orientation object constancy - Form of hand constancy - Even though visual features have chaged drastically - Cells is indifferent from orientation don’t know how is doing it - Not simple features but objects - What is hand is when cells fire - Strip features - Response decrease – rise of mittien lost features that is hand - If cell is driven by higj level objects or features is deconrontruct object into parts - Cell smart enough to distinguish, not think it hand is bec part of brain not respond to it as a hand - May complex objects but face not respond - Object specificity not in v1 or v2 posterior but move up ventral stream object Pictionary in brain Dorsal - Whole in back relatively larger fields then ventral - Coming from rods and lot more convergence more periphery - Receptive fields bigger - Some infor from central vision - What is all central vision all in fovea Nueroimaging - Edu in science read of studies and look at data much less clear - Evidence but is somewhat iffy - Homologue for object dicrimation or location - All same objects a is location land mark dis - 3 objects a first and b new location and track location or object - Shirt change location - Location but also in terms of object - Change into another object - Attend to change location or type of object - Change in object ind of chamge in location act in red area act in ventral stream - And ignore what and focus where act to dorsal visual patheway in parietal lobe - In intact brains act v and d pathways Disorders - Evidence from human stroke patients - Stroke randon assignment - Tes behviour and look at scans to see parts of damage and before scanners disorders of v and d called cisual agnosia - Peculiar to person - Agnosia is to see without knowing – deficit in knowldeg through vision - Modiality specifici – agnosia deficit in vison not global deficit example memory - Agnosia identify key not able through vision if pick up and jingle say keys - Not deficit in general intelligence or ec given other features form of blindness but still see - Visual system broken impairs ability to access info - Dementia may see keys in normal sense draw what see but demented loss lot of hipp or ass lnowldege strucuture s ke y in hand lost knowledge central knowldeg to say what something is - 3 - Lissauer app and ass - App – more basic form - Ass – higher order of brain damage where vision intact knwokdege impaited - Pros – ass subcat is prosp - Stoke in most anterior ventral stream hands gone – not see hands - Those not important for face not rec hand but rec other complelx object - Rare depends on brain damage - Cluster are right next to each other rare just delete hand cells - Case studies - Deficits in face perc is propo App - Not - Not cortical blindness – not retinal blindness – these see light do see - Visual field test is intact - Not deficit in process visual info - V1 not able to see objects but things of retina - Low level deatures intact Is - Deficit in forming a percpet - Percept – mental impression of something based on the senses - Orginaized some way to see it as an object - On retina jumble of features percept linked certain form needs binding together - They see but scattered not for, coherent percepts Appre beh - Not in specified location – not respect boundaries of brain - Cytoarchictect not look and sperated and next and distinct areas when have lesion not withing broadmann areas not confined to certain area - Some 18 17 and all 19 variety of deficits not single area but many areas - Kind of perc problems depends on lesion extent - Ask to draw things - See picking up on some data not key but number of features - Not forming a percept - Part of system org into single object not little features but see it as a thing - Even if see object first time - Brain form percept even not extract anything from it- what is impaired in individuals - Right looks like create facisimile but look closely not drew what look like but but how draw - Not draw two squares of circles but lines - Not mental impression of two squares of circles but orientation and curvature - They are seeing but some part of early system organizes it Next - Higher is object constancy – not rely on data on retina bc car looks diff retina depending cvisula angel you reco it - Some level of form rec but when asked say what it is – relying on visual data little interference can throw them off not prcesses to fill in missing parts - Cast heavier shadows see same thing is imoaired – some kind of constancy taking in liht effects brain cant compute under light conditions - Unusal use test – non concial view – conical view of stapler and this one never see it like bottom out of context scratch head but visual system be able to do mental arithementic – their visucal data is disntinct we can over come that - Pale same is hard to do – expert perceiver brain has to do this even data look different Evidence - Loc – ventral view of brain medial - Apprecirive – mid level visual areas intermideate before sending to higerh levels object specific between v1 and higher are regions calcl object constancy - Patients damamge to middle rep impaired object constancy - Fmri - Healthy humans loc is supporting some sort of object constancy - Data change but still hand – computation brain has to make - Not measure single neurons but blood flow - Loc has object constancy – neurons respond to shape if occluded or not - Respond as if nothing has changed - Simple shapes - C and d yellow and orange - Same shape one is occluded in is not in c - And d is identical - Parts of brain responding to not occluded - Neurons responding the same - Measuring bold signle – measuring blood oxygenation response - If processing see change in oxygentation utilization and blood - Hemodynamic response – dynamics of hemoglobin - Measuring frm neurons spike and blood look at curve - Time – neurons fire at microsec the blood flow is over 10 seconds - .01 is when stimulus is shown 5 seconds later measure blood flow response - Magnitidue of bold response is signal – how much neurons fire - Brain sees something again reptiation reduction or adaptation– decreases response to it – repitiation related adaptation - Shown in yellow or orange is second pres of objects - Rediction – brain I have seen this before - Brain new object same response as wen first shown - No reduction – no memory for it - Used fmri to map out brain constancy - One is identical object another is same shape - Before higher order is constancy - May show up in exam - Loc – what parts of brain despite visual changes not showing reduction and links to - Lesion data midlevel cause deficits objects look differtn not same - And fmri when brain is intact Ass agnosia - Not - can form perceptual grouping - Higher order visual defict - Vision is highly orgnazied – can see objects not extract infor from visual system to say what the object is - Extra step to say what it is – visual system forms the image - Access semintac information or meaning from visual objects - Psychic bliondness in 1890 psychological blindness - See colours and forms but not know what it is - Can draw them paintings lost knowldeg get from v
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