Reduced facilitation effect of collinear flankers on contrast detection reveals impaired lateral connectivity in the visual cortex of schizophrenia patients.

The aim of this study was to investigate lateral connectivity in early visual cortex of schizophrenia patients. Contrast thresholds were measured for centrally presented Gabor patches which were surrounded by two collinear or orthogonal flankers. The healthy subjects (n = 15) showed lower contrast thresholds for central Gabor patches when collinear flankers were presented. This effect was significantly reduced in unmedicated highly functioning schizophrenia patients (n = 20) who performed normally on the continuous performance test. The performance of the patients did not correlate with the positive and negative symptoms. The facilitation effect of collinear flankers is believed to reflect lateral interactions between feature-specific units in early visual cortex (V1). Our results therefore suggest abnormal lateral interactions in early visual cortex of schizophrenia patients.