Is frontal lobe involved in the generation of auditory evoked P50?

This study examined the functional substrate of P50 suppression. Auditory e voked potentials (AEPs) and magnetic fields (AEFs) were recorded from healt hy subjects simultaneously and analyzed using spatio-temporal source analys is. The resulting equivalent dipole model for the AEP consisted of one sour ce in the auditory cortex (AC) of each hemisphere and an radially oriented medial frontal source, both with maximum AEP activity around 50 ms. The fro ntal source was functionally separated from the AC sources since it peaked significantly later and showed significantly larger P50 amplitude suppressi on. P30m showed neither suppression nor substantial frontal activity. In su m, this study relates P50 suppression to reduction of AC source activity an d is the first to yield direct evidence for frontal involvement in P50 supp ression. NeuroReport 12:3303-3307 (C) 2001 Lippincott Williams. & Wilkins.