Contextual suppression and protection in schizophrenic patients
INTRODUCTION: Contextual processing is often strongly deteriorated in schizophrenic patients as found, for example, in higher cognitive as well as lower visual paradigms. In visual detection tasks, impoverished contextual facilitation was attributed to aberrant excitatory neural circuits. On the other hand, we found contextual suppression, possibly related to neural inhibition, to be fast and intact in a visual backward masking task. Here, we combine a suppressive with a "protective" paradigm to further our understanding of the contextual deficiencies of schizophrenic patients in visual information processing. METHODS: Twenty three schizophrenic patients and 18 healthy controls were asked to discriminate the offset direction of a vernier target, which was followed by one of a variety of masks for several stimulus onset asynchronies (SOAs). RESULTS: As in previous studies, patients needed clearly longer SOAs than controls. However, when longer SOAs were taken into account, increases as well as decreases in backward mask strength had comparable effects in patients and controls. CONCLUSIONS: From these results, we suggest that complex spatial processing is fast and intact in schizophrenic patients.