Is P50 Suppression a Measure of Sensory Gating in Schizophrenia?

Background:Abnormal P50 response has been hypothesized to reflect the sensory gating deficit in schizophrenia. Despite the extensive literature concerning the sensory filtering or gating deficit in schizophrenia, no evidence has been provided to test the relationship of the P50 phenomenon with patientsʹ experiences of perceptual anomalies. Methods:Sixteen drug-free DSM-IV diagnosed schizophrenic patients who reported moderate to severe perceptual anomalies in the auditory or visual modality were examined as compared to 16 schizophrenic patients who did not report perceptual anomalies, and 16 normal subjects. Both control groups were age- and gender-matched with the study group. Results:Patients reporting perceptual anomalies exhibited P50 patterns that did not differ from normal subjects. In contrast, patients who did not report perceptual anomalies showed the abnormal P50 ratios previously found to be associated with schizophrenia. Conclusions:These paradoxical findings do not support the hypothetical relationship between the P50 and behavioral measures of sensory gating, suggesting that additional studies are needed to further explore the clinical correlates of the P50.