As can be seen in Fig. 1, the amplitude of P3 to both novels and targets was overall smaller in depressed patients than in healthy controls. ANOVA of amplitude in the P3 window (220–470 ms) confirmed the existence of a significant Group difference, F = 6.06, df = 1, 38, P = 0.018. There was also a trend for a Group by Stimulus interaction (F = 3.01 df = 2,76, P = 0.06, ε = 0.91). Analysis of simple effects indicated that the group difference in P3 amplitude was significant for novel stimuli (F = 6.23, df = 1,38, P = 0.017; effect size = 0.80), but not for target (F = 3.44, df = 1,38, P = 0.072; effect size = 0.59) or nontarget stimuli (F = 2.96, df = 1,38, P = 0.094; effect size = 0.56). Fig. 2 shows the mean amplitude of the novelty P3 and target P3 for depressed patients and controls at midline sites. At the parietal site, where the target P3 was maximum, patients had significantly smaller novelty P3 than controls (t =
