Reduced crowding and poor contour detection in schizophrenia are consistent with weak surround inhibition

Abstract

People with schizophrenia (SZ) exhibit deficits in visual processing, including markedly poor detection of extended contours. Although this has been attributed to a deficit in binding or global integration – i.e. an inability to pool local structure across space – here we present evidence that it likely originates from a combination of poorer local processing (in this case, of orientation) combined with abnormal processing of visual context. We first report that although patients are poorer at detecting contours embedded in random noise they are proportionally less disrupted by the presence of near-parallel surrounds than healthy controls (consistent with earlier reports of reduced surround suppression in SZ). Second we show that patients’ ability to report the orientation of the local components of these contour patterns is (a) poor and (b) also less affected by the disruptive influence of distractor elements (visual crowding). We suggest that reduced sensitivity to local orientation, and to orientation-context, could result from abnormal gain control which is implicated both in the generation of orientation-tuning in visual cortex and in surround suppression.

Meeting abstract presented at VSS 2012