Vision---UCSD-Cognitive-Science視覺-認知科學課件

1、VisionVision 1: Filling-in, Color, Motion, FormVisual PathsFilling-InPerceptual CompletionConceptual CompletionColorMotionFormAgnosiaProsopagnosiaFilling-InUsually, function of a brain area is deduced from deficits correlated with damage to that areaIn the case of filling-in, brain function is deduc

2、ed from intact abilities (perceptions) in the absence of sensory inputFilling-In: Perceptual CompletionPerceptual Completion in NormalsProbably due to excitatory horizontal connections in V1Filling-In Resulting From V1 DamageFrom scotomas (“hole” in V1)Hemianopias*DIGITAL VIDEO: Hemianopia Perceptua

3、l Filling-InRamachandran patient:Filled in texture/surfaces but not objectsFilled in numbers but looked like hieroglyphics/couldnt identifyFilling in occurs at different speeds for different perceptual attributesCouldnt fill in facesLessons From Filling In: Perceptual CompletionBrain uses statistica

4、l regularities to fill in.This act of interpolation saves an enormous amount of computation.Perhaps due to lateral horizontal connections in cortical areas higher than V1?Conceptual CompletionAdditional parietal damageCharles Bonnet SyndromePatients Know Hallucinations Arent Real Because:Others corr

5、ect themFade after a few secondsHighly improbablySomething odd about the images (too vivid, cartoonish, etc.)Lessons From Filling-In:Conceptual CompletionParietal Damage? Back-Projections?Disorders of Color ProcessingCentral AchromatopsiaDeficit in color perception caused by an acquired cerebral les

6、ion Tested WithColor plate test (e.g., Ishihara Color Plate Test)Color arrangement test (e.g., Farnsworth-Munsell 100-Hue Test)Pass color chips across the visual fieldCentral Achromatopsia Disorder of Color PerceptionNature of the impairment uncertainReduced hue discrimination Deficient color consta

7、ncyCo-occurs often with alexia or visual agnosiaV4 damage most likely siteLingual gyrus, fusiform gyrus, or white matter between the regionsV4 DamageDisorder of Color ImagerySeems that defective color perception invariably results in defective color imageryImagining an objects color (e.g., a yellow

8、banana) requires an least some of the neural representations required to perceive colorPatient cannot “remember” the color of items that need to be imaginedColor Agnosia Disorder Of Color RecognitionPerform fine on color matching tasksExhibit errors in matching colors to objectsMay still have semant

9、ic knowledge about colors Not yet well-distinguished from color perception disorder Behavioral manifestations Site of damageCerebral Akinetopsia:Motion BlindnessCerebral Akinetopsia: Motion BlindnessDeficit of motion processing caused by acquired cerebral lesionsBecause motion cues serve many purpos

10、es, a range of deficits can resultE.g., Difficulty using motion to find objects (structure for motion or kinetic depth) Pursuit eye movements impairedL.M. Case DescriptionCould see slowly moving targetsFaster ones materialized at successive positions with no movement in betweenDid not perceive appar

11、ent motionReduced perception of motion after-effectsSaw changes in position not depth for objects moved towards her*Motion after-effect illusion for demoL.M. Case DescriptionGood static visual acuity perceptionPerception of tactile and acoustic motionAccurate localization of visual targets by saccad

12、ic eye movementsNo visual field defect for formNo neglect of visual targets flashed simultaneously in both hemi field Relative preservation of face and object recognition, reading, and color visionV5 DamageMotion Blindness:Neuroanatomical LocusDamage Parietal-temporo-occipital, near angular gyrus Pa

13、rieto-occipitalAs part of a more pervasive disturbance (Balints syndrome or Alzheimers disease)L M and others: superior temporoparietal Includes the cortical areas of 19 and 37, which are adjacent (may resemble monkeys area MT / V5)The homologies between motion processing areas in monkey and human m

14、ay not be as close as they once appeared.Severe deficits of motion perception can also occur with lesions in parietal insula and midline cerebellumWHAT, WHERE, & HOW SYSTEMSWhat, Where, & How SystemsWhatVisual AgnosiaVisual Object AgnosiaApperceptiveAssociativeApperceptive AgnosiaIntact vision:Acuit

15、y, brightness discrimination, color vision, & other elementary visual capabilitiesSometimes preserved shape from motionDeficits:Abnormal shape perception (pictures, letters, simple shapes)Grouping process deficit (that operates over an array of local features representing contour, color, depth, etc.

16、)Apperceptive AgnosiaVIDEO: Apperceptive Agnosia, impaired triangle recognition, subject 1VIDEO: Apperceptive Agnosia, impaired object recognition, subject 1VIDEO: Object Agnosia 2: Impaired Visual but not tactile identification (naming), subject 2VIDEO: Object Agnosia 3: Intact visual movement iden

17、tification, subject 2VIDEO: Object Agnosia 1: Impaired Visual identification (subject given name & array of objects), cant see objectsAssociative AgnosiaAssociative AgnosiaCannot recognize objects by sight aloneIntact general knowledge of objectsCan recognize objects by touch or definitionVisual per

18、ception better than in apperceptive agnosia Not a naming deficit (cannot indicate recognition by nonverbal means)Theories of Associative AgnosiaDisconnection between visual representations and language areasDisconnection between visual representations and memory areasStored visual memories have been

19、 damagedA perceptual and memory problem, and the two are inseparableIntertwined Perception & MemorySome visual problems Copying drawings on line by lineOn matching tasks, they rely on slow, sequential featured-by-feature checkingIn the PDP system, the memory of the stimulus would consist of a patter

20、n of connections strengths among a number of neuron like units. The perceptual representation resulting from presentation of the stimulus will depend upon the pattern of connection strengths among the units directly or indirectly activated by the stimulus. Thus, if a memory is altered by damaging th

21、e network, perception will be altered as well. Thus, Associative Agnosia may not be the results of an impairment to perception or to memory; rather, the two are in principle inseparable, and the impairment is better described as a loss of high level visual perceptual representations that were shaped by, and embody the memory of, visual experience.Apperceptive:Localization of DamageDiffuse brain damage, often from carbon monoxide poisoningApperceptive AssociativeAssociative AgnosiaProsopagnosiaProsopagnosiaCompensa