News/Notices

Feb. 17, 11:45, Wei Ji Ma. Optimality and Probabilistic Computation in Visual Categorization

Brian Keane

Department of Psychiatry, UMDNJ

Conceptual contributions to perceptual completion deficits in schizophrenia

Perceptual completion is the process by which the visual system combines contour information over space and time to represent object shape and number. Perceptual completion is compromised in schizophrenia, but the mechanisms underlying the impairment are unclear. In this talk, I make the case that the deficit arises at conceptual levels of processing.  In the first part of the talk, I present behavioral data that indicates that schizophrenia patients are normal at forming illusory contours, normal at filling-in between collinear Gabors, but impaired at a later shape integration stage.  I then show that healthy individuals can be biased to exhibit schizophrenia-like behavior on a perceptual completion task, once they are asked to conceptualize configurations as fragmented rather than unitary. Finally, I show that patients’ ability to represent perceptually completed shape is dramatically reduced when they manifest high levels of conceptual disorganization.  This evidence, considered jointly, suggests that perceptual completion deficits in schizophrenia arise not from early contour linking but instead from a lessened ability to conceptualize a fragmented visual world. 

Background reading:

Keane_2012_Cognition.pdf

Keane_2012_Exp Brain Res.pdf