PSYC213_Lecture5.docx - PSYC213 \u2013 Lecture 5 \u2013 Visual perception Context and Theories Last Class Sensation Energy from a physical stimulus in the

PSYC213_Lecture5.docx - PSYC213 u2013 Lecture 5 u2013...

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PSYC213 – Lecture 5 – Visual perception: Context and Theories Last Class Sensation : Energy from a physical stimulus in the environment that is picked up by sense organs Perception : Follow sensation. When the brain sensed information and translates it into something meaningful McGurk effect and the brain o Compared brain activity for people who experienced the McGurk effect and those people who did not experience this effect o This left superior temporal sulcus is important for audiovisual integration during speech perception More active for people who experience the McGurk effect Individual differences are seen in the brain! Early visual system o Step 1: Light waves enter the eye and are focused onto the retina, a thin layer of tissue at the back of the eye o Step 2: Photoreceptors in the retina convert light to electrical activity o Step 3: This electrical signal is sent to bipolar cells then ganglion cells o Step 4: This signal exits through the optic nerve to be sent to the brain Functional specialization Retinotopic map in the primary visual cortex o Visual Association Area: Interprets information acquired through the primary visual cortex o Primary Visual Cortex: Size, color, light, motion, dimensions Two pathways form the visual cortex o What (ventral) pathway Object recognition o Where (dorsal) pathway Spatial location If damaged, motion perception is impaired Akinetopsia o World 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 Agnosia o Damage to the visual processing areas (the what pathway) of the brain that result in selectrive problems regonizing objects Basic sensory systems are intact Supports a dissociation between being able to see visual features and interpreting those visual features The specific area of the brain that is damaged determines which types (or features) of objects cannot be recognized Supports high level functional specialization Prosopagnosia o A form of visual agnosia o An inability to recognize faces while still being able to recognize other visual objects o Damage to fusiform face area o Different forms Problem perceiving faces Faces look contorted Problem attaching meaning to faces Faces cannot be identified o Different causes Acquired (brain injury) Congenital (genetic) Apperceptive visual agnosia o A failure to recognize objects because of problems perceiving the object o This is not a deficit in sensory processing These cases can detect visual features o This is a problem with grouping visual features into a meaningful perception o Evidence These cases cannot copy a simple line drawing
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