Slow brain potentials and psychomotor retardation in depression.

Event-related cortical potentials were recorded in 11 patients with primary depression and 11 healthy control subjects during a serial choice reaction task. Each new trial was voluntarily initiated when the subject pressed a microswitch; an acoustic go or no-go signal followed after a fixed interval. This elicited a Bereitschaftspotential (BP), a contingent negative variation (CNV), acoustically evoked potentials (N1, P2, P3), and a post-imperative negative variation (PINV) in direct succession. These were evaluated conventionally and by principal component analysis (PCA). Patients exhibited significantly longer reaction times and more negative PINVs. BP and CNV did not differ between groups. In conventional amplitude measurement small P3 amplitudes in depressives may be feigned by markedly negative PINVs.