Individuals having a depressive disorder commonly experience difficulties in concentration or attention and other cognitive functions, most notably memory and executive function (Austin et al., 2001; Porter et al., 2003). The P3 or P300 event-related brain potential (ERP) provides physiologic measures associated with attentional engagement and memory operations during cognitive task performance (Polich, 2007). The study of P3 in depressed patients could therefore provide information concerning the neurophysiologic mechanisms underlying their cognitive deficits. There have, however, been conflicting reports as to whether or not depressed patients have reduced P3 amplitude. An early review found that about half of the studies showed reduced P3 amplitude in depressed patients when compared to normal controls (Roth et al., 1986). We reviewed the findings of more recent studies that compared P3 amplitudes for depressed patients and healthy controls in auditory target detection (oddball) tasks (Bruder et al., submitted for publication). Ten studies found significantly smaller P3 amplitude in depressed patients as compared to healthy controls (Blackwood et al., 1987; Muir et al., 1991; Gangadhar et al., 1993; Ancy et al., 1996; Wagner et al.,
