Perceptual organization, which refers to the ability to integrate fragments of stimuli to form a representation of a whole edge, part, or object, is impaired in schizophrenia. A contour integration paradigm, involving detection of a set of Gabor patches forming an oval contour pointing to the right or left embedded in a field of randomly oriented Gabors, has been developed for use in clinical trials of schizophrenia. The purpose of the present study was to assess contributions of early and later stages of processing to deficits in contour integration, as well as to develop an event-related potential (ERP) analog of this task. Twenty-one patients with schizophrenia and 28 controls participated. The Gabor elements forming the contours were given a low or high degree of orientational jitter, making it either easy or difficult to identify the direction in which the contour was pointing. ERP results showed greater negative peaks at ~165 (N1 component) and ~270 ms for the low-jitter versus the high-jitter contours, with a much greater difference between jitter conditions at 270 ms. This later ERP component was previously termed Ncl for closure negativity. Source localization identified the Ncl in the lateral occipital object recognition area. Patients showed a significant decrease in the Ncl, but not N1, compared to controls, and this was associated with impaired behavioral ability to identify contours. In addition, an earlier negative peak was found at ~120 ms (termed N120) that differentiated jitter conditions, had a dorsal stream source, and differed between patients and controls. Patients also showed a deficit in the dorsal stream sensory P1 component. These results are in accord with impairments in distributed circuitry contributing to perceptual organization deficits and provide an ERP analog to the behavioral contour integration task.
Keywords: schizophrenia, perception, cognition, contour integration, electrophysiology, vision
Citation: Butler PD, Abeles IY, Silverstein SM, Dias EC, Weiskopf NG, Calderone DJ and Sehatpour P (2013) An event-related potential examination of contour integration deficits in schizophrenia. Front. Psychol. 4:132. doi: 10.3389/fpsyg.2013.00132
Received: 31 January 2013; Accepted: 03 March 2013;
Published online: 21 March 2013.
Edited by:Michael Green, University of California, Los Angeles, USA
Reviewed by:Jeffrey Bedwell, University of Central Florida, USA
Copyright © 2013 Butler, Abeles, Silverstein, Dias, Weiskopf, Calderone and Sehatpour. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.
*Correspondence: Pamela D. Butler, Schizophrenia Research Division, Nathan S. Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd., Orangeburg, NY 10962, USA. e-mail: firstname.lastname@example.org