Evidence from Lesions: Agnosia • Lesions (especially in the left hemisphere) of the inferior temporal cortex lead to disorders of memory for people and things • recognition and identification are impaired – prosopagnosia is a specific kind of agnosia: inability to recognize faces
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Evidence from Lesions: Agnosia Lesions (especially in the left hemisphere) of the inferior temporal cortex lead to disorders of memory for people and things.
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Evidence from Lesions: Agnosia
• Lesions (especially in the left hemisphere) of the inferior temporal cortex lead to disorders of memory for people and things
• recognition and identification are impaired– prosopagnosia is a specific
kind of agnosia: inability to recognize faces
• explicit (conscious) decisions about object features are disrupted
Ventral lesions can decouple awareness from action
• Goodale and Milner – Patient DF
• Patient could not indicate the orientation of a slot using her awareness
• Patient could move her hand appropriately to interact with the slot
– whether visually guided or guided by an internal representation in memory
Ventral lesions can decouple awareness from action
• Single dissociation of action from conscious perception
• Dorsal pathway remained intact while ventral pathway was impaired
• Dorsal Pathway seems to guide motor actions, at least for ones that need spatial information
• Activity within the Dorsal Pathway seems not to be sufficient for consciousness
Lesions of “Retinostriate” Pathway
• Lesions (usually due to stroke) cause a region of blindness called a scotoma
• Identified using perimetry• note macular sparing
• Blindsight patients have since been shown to posses a surprising range of “residual” visual abilities– better than chance at detection and discrimination of some
visual features such as direction of motion
• These go beyond simple orienting - how can this be?