Evoked potentials, expectancy wave, and skin resistance in depressed patients and healthy controls.

Averaged evoked potentials, expectancy waves and number and amplitude of skin resistance responses to auditory stimuli are found to be significantly smaller in a group of 18 patients with primary depression than in 27 healthy controls. AEP amplitude attenuation is shown not to be an averaging artifact, due to varying response latencies. There are no simple relations between electrocortical and electrodermal parameters, but patients display more significant correlations between these two sets of variable than controls. Amplitude attenuations are interpreted as hyporesponsivity resulting from depressive inhibition. The narrower coupling of variables in the depressed group is viewed as a limitation in physiological plasticity.