PSYC213_Lecture5.docx - PSYC213 \u2013 Lecture 5 \u2013 Visual perception Context and Theories Last Class Sensation Energy from a physical stimulus in the
PSYC213 – Lecture 5 – Visual perception: Context and TheoriesLast ClassSensation: Energy from a physical stimulus in the environment that is picked up by sense organsPerception: Follow sensation. When the brain sensed information and translates it into something meaningfulMcGurk effect and the brainoCompared brain activity for people who experienced the McGurk effect and those people who did not experience this effectoThis left superior temporal sulcus is important for audiovisual integration during speech perceptionMore active for people who experience the McGurk effectIndividual differences are seen in the brain!Early visual systemoStep 1: Light waves enter the eye and are focused onto the retina, a thin layer of tissue at the back of the eyeoStep 2:Photoreceptors in the retina convert light to electrical activityoStep 3:This electrical signal is sent to bipolar cells then ganglion cellsoStep 4:This signal exits through the optic nerve to be sent to the brainFunctional specializationRetinotopic map in the primary visual cortex oVisual Association Area: Interprets information acquired through the primary visual cortexoPrimary Visual Cortex: Size, color, light, motion, dimensionsTwo pathways form the visual cortexoWhat (ventral) pathwayObject recognition oWhere (dorsal) pathwaySpatial location If damaged, motion perception is impairedAkinetopsiaoWorld is like a series of snapshots o“When I’m looking at the car first, it seems far away. But then when I want to cross the road, suddenly the car is very near.” Patient with Akinetopsia Visual AgnosiaoDamage to the visual processing areas (the what pathway) of the brain that result in selectrive problems regonizing objectsBasic sensory systems are intactSupports a dissociation between being able to see visual features and interpreting those visual featuresThe specific area of the brain that is damaged determines which types (or features) of objects cannot be recognizedSupports high level functional specialization ProsopagnosiaoA form of visual agnosiaoAn inability to recognize faces while still being able to recognize other visual objectsoDamage to fusiform face area oDifferent formsProblem perceiving facesFaces look contortedProblem attaching meaning to facesFaces cannot be identifiedoDifferent causesAcquired (brain injury)Congenital (genetic)Apperceptive visual agnosia oA failure to recognize objects because of problems perceiving the objectoThis is not a deficit in sensory processingThese cases can detect visual featuresoThis is a problem with grouping visual features into a meaningful perceptionoEvidenceThese cases cannot copy a simple line drawing