The P300 Event-Related Brain Potential in Psychiatric and Neurological Diagnosis

Abstract

The electroencephalogram (EEG) is the record of voltage recorded from the human scalp (as a function of time) that is thought to be attributable to underlying cortical (brain) activity. P300 (P3) is an EEG-derived event-related potential (ERP) recordable from the human scalp using EEG-type electrodes and physiological recording parameters (for a detailed description, see Fabiani, Gratton, Karis, & Donchin, 1987). The word “event” in “event-related potential” refers to the external physical or internal psychological event that causes the deflection (in the ongoing EEG) that defines the ERP. A quarter of a century ago, the term “evoked potential” was used to describe EEG deflections caused by external stimuli (e.g., light flashes, tones). The deflections were known to be related to cortical sensory neuronal activity occurring synchronously on the arrival in the cortex of the neuronal activity evoked by the discrete sensory—physical event. It is now known that other events, i.e., events not of a sensory nature, are also associable with distinct EEG deflections, and thus the more general term ERP was developed and understood to include such special cases or subcategories as sensory evoked potentials. Hillyard (1985) has provided a concise review of the approximately half dozen well-studied psychologically related ERPs, including the P3 wave.