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Is frontal lobe involved in P50 generation?

Regina Weisser 1, Matthias Weisbrod 1, Miriam Röhrig 2, André Rupp 2, Michael Scherg 2

1 Psychiatric Department, University of Heidelberg
2 Section of Biomagnetism, Neurologic Department, University of Heidelberg

This study examined the functional substrate of P50 suppression. Auditory evoked potentials (AEPs) and magnetic fields (AEFs) were recorded from healthy subjects simultaneously and analyzed using spatio-temporal source analysis. The resulting equivalent dipole-model for the AEP consisted of one source in the auditory cortex (AC) of each hemisphere and an radially oriented medial frontal source, both with maximum AEP activity around 50 ms. The frontal source was functionally separated from the AC sources since it peaked significantly later and showed significantly larger P50 amplitude suppression. P30m showed neither suppression nor substantial frontal activity. In sum, this study relates P50 suppression to reduction of AC source activity and is the first study to yield evidence for frontal contribution to P50 suppression.