EEG of interimpulse intervals during habituation of auditory evoked potentials in depressed moods.

Abstract

1. With the averaging of the EEG of the entire interimpulse interval in the procedure investigating the habituation of auditory evoked potentials (EPs) in healthy individuals and endogenous depression patients in the averaged EP-EEG, a “rhythmical wave process” (RWP) appeared, especially pronounced in the patient group. 2. The RWP appeared or became more marked in successive averagings across the 10 realizations completing each series of 30 stimuli. It significantly predominated in the patients, often making more difficult the identification of the EPs, and not infrequently was maintained in the averages of all 120 realizations, with an amplitude comparable to the amplitude of the basic components of the EP or even exceeding it. A reliable correlation of the parameters of the RWP with the indices of melancholic mood was identified in both the patients and the well subjects. 3. The RWP may be regarded as a special manifestation of perceptual defense in individuals in whom “internal distraction” as the result of depression mood leads to the engagement of mechanisms of active isolation from the external world.