Preparatory brain potentials in major depressive disorder.

1. Psychomotor slowing in depression is frequently reflected by delayed reaction times (RT). 2. The role of central arousal mechanisms in response slowing was examined by comparing scalp-recorded slow negative potentials of depressed patients with normal controls in two separate studies. 3. Varying fore-warned RT conditions elicited contingent negative variation (CNV) waveforms and the resultant mid-point amplitudes of these waveforms together with orienting (O-wave), expectancy (E-wave) and post-imperative negative variation (PINV) component amplitudes and sensory evoked responses (N1, P2) were compared between groups. 4. RTs were significantly slowed in depressed patients and the patient group exhibited consistently larger PINV amplitudes. Depending on the RT condition, patients also exhibited larger mid-point CNV amplitudes and smaller N1 and P2 amplitudes.