Summary:Event-related potentials are time-locked electric fields that arise from synchronous neural activity associated with cognitive processing. The P3 is a scalp-recorded positive component that has been linked to memory mechanisms. The effects of memory disorders and focal cerebral lesions on the P3 vary widely as a function of the cognitive task used to elicit the waveform. These findings suggest that multiple antecedent processors or multiple generators contribute to the potential. The P3 may be generated primarily by the neocortex under modulation of subcortical projections such as the basal forebrain cholinergic system. Although the functional role of the P3 is uncertain, it is possible that P3 is related to a subcomponent of memory.