No abstract

How the various features of an object are bound to a unified percept is one of the most fundamental problems the human brain has to solve. Whereas healthy observers usually do not reveal binding errors, it has been proposed that schizophrenic patients suffer from binding deficits. To elucidate such deficits, we investigated one of the most basic binding or integration paradigms: feature fusion. In feature fusion, two stimuli are presented in rapid succession. Using a vernier paradigm, we could, recently, show that the second stimulus determines feature fusion more strongly than the first one (Herzog et al. 2003). However, the first presented stimulus determines feature fusion when a grating follows the two stimuli. Reversal of dominance has occurred. In this study, we show that schizophrenic patients reveal qualitatively the same integration characteristics in feature fusion as healthy controls do. Hence, although some aspects of visual processing are strongly disturbed in schizophrenia as revealed by masking studies, feature fusion appears to be, at least qualitatively, spared. Our fusion paradigm allows one to investigate intact and deficient visual processing in schizophrenic patients with great detail and to elucidate the nature of deficits of visual processing in schizophrenia.

In patients with schizophrenia, early as well as late stages of information processing can be deficient. Therefore, it is important to determine the earliest occurrences of aberrant processing since deficits on these stages may cause abnormal processing on later, e. g. cognitive, levels. In order to investigate this issue in the visual domain, we studied one of the most basic feature integration mechanisms, namely feature fusion. Our results indicate that in schizophrenic patients this integration mechanism is qualitatively intact but reveals quantitative impairments that may influence later processing stages.