klab
"What I cannot create, I do not understand." – R. Feynman
Lee H. de-Wit, Jonas Kubilius, Hans P. Op de Beeck, Johan Wagemans

A reversal of part-whole Gestalts in a patient with visual form agnosia

OCCAM , 2013-05-30 slides poster at AVA 2012

For many visual phenomena the ‘whole’ is not just different from the sum of its ‘parts’, but these parts seem to become lost or inaccessible. Neuroimaging (Kubilius, Wagemans, Op de Beeck, 2011) suggests that this increased behavioral sensitivity to ‘wholes’ over ‘parts’ reflects the way in which visual input is integrated as it progresses from V1 to LOC. More specifically while early visual areas may contain more information about parts (edges), higher areas contain more information about wholes (shapes). Typical behavior is consistent with a ‘read-out’ of information from these higher areas. In this research we test how information is read-out from the visual hierarchy using patients who have lesions to higher stages of visual processing. We will focus on the results from patient DF, who demonstrates better access to parts than to wholes in the configural superiority effect used by Kubilius et al. This result demonstrates how compelling Gestalts can break down with selective lesions to the ventral stream, particularly area LO. We will use a simulation of h-MAX to demonstrate that the behavior of the our patient can be understood in terms of a read out of information from V1 (which is preserved in this patient). This combination of neuroimaging, modeling, and patient neuropsychology potentially provides a useful tool for investigating not only how visual input is processed, but also to test how information is read-out from the hierarchy of visual areas.