Despite P3’s maximal amplitude over parietal areas in response to targets when scalp electrodes are used, studies with electrodes inserted into the brain (i.e., depth electrodes) in humans indicate that P3s originate in the frontal cortex; the hippocampus, which is important in the consolidation of new memories; and the amygdala, a part of the limbic system involved in producing and controlling emotional behavior. Recent functional magnetic resonance (fMRI) studies support these findings and implicate another part of the limbic system, the anterior cingulate area of the frontal cortex, as critical for P3 generation. The lower amplitude P3 components, along with the weaker and less well organized sources in alcoholics, suggest disorganized and inefficient brain functioning. This global neurophysiological pattern suggests cortical disinhibition, providing further support for underlying CNS hyperexcitability in alcoholics.
