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 X

“Retinocollicular” Pathway independently mediates orienting Rafal et al. (1990) subjects move eyes to fixate a peripheral target in two different conditions: –target alone

Retinocollicular Pathway independently mediates orienting Rafal et al. (1990) subjects move eyes to fixate a peripheral target in two different conditions: –target alone –accompanied by distractor

Retinocollicular Pathway independently mediates orienting Rafal et al. (1990) result Subjects were slower when presented with a distracting stimulus in the scotoma (359 ms vs. 500 ms) Residual vision in cortical blindness has been called “blindsight”

Retinocollicular Pathway independently mediates orienting 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?

Retinocollicular Pathway independently mediates orienting Recall that the feed-forward sweep is not a single wave of information and that it doesn’t only go through V1 In particular, MT seems to get very early and direct input

Retinocollicular Pathway independently mediates orienting Recall that the feed-forward sweep in not a single wave of information and that it doesn’t only go through V1 In particular, MT seems to get very early and direct input Information represented in dorsal pathway guides behaviour but doesn’t support awareness