Sensory gating and source analysis of the auditory P50 in low and high suppressors.

Impairments in sensory gating in schizophrenia have been reflected by diminished suppression of the scalp-recorded middle latency auditory P50 event-related potential (MLAERP) elicited by the second (S(2)) of a pair (S(1)-S(2)) of clicks. As understanding the functional neural substrates of aberrant gating would have important implications for schizophrenia, this study examined the location and time-course of the neural generators of the P50 MLAERP and its gating on subgroups of healthy volunteers exhibiting low (n=12) and high (n=12) P50 suppression. Suppressor differences were observed with S(1) P50 (high>low) and S(2) P50 (high<low) amplitudes, and current source density analysis with standardized Low Resolution Electromagnetic Tomography (sLORETA) evidenced an S(1) P50-related activation of limbic, temporal and parietal regions in the high but not the low suppressors. Distributed source localization of the Gating Difference Wave (GDW), obtained by subtracting the S(2) P50 response from the S(1) P50 response, also revealed a later and sustained frontal activation to characterize high suppressors. These findings suggest that impaired gating of the kind evident in schizophrenia may involve the deficient functioning of multiple interconnected and temporally overlapping activated brain regions.