Neurophysiological Сorrelates of Threatening Information Expectations in Nonpsychotic Endogenous Depression

Abstract

We explored the unconscious expectations of threatening and neutral visual information in patients with endogenous depression and in healthy volunteers of the same age. Multichannel EEG was recorded at 500 Hz when participants categorized monochrome images of people and animals. We used four categories of stimuli, two of which were neutral and the other two were threatening. The warning stimuli (four simple figures, one for each category) were presented for 2 seconds before the actual images, and this association was not explained to participants. After the categorization, the participants evaluated images as neutral or emotional. We analysed behavioral indicators (motor reaction time and error rates) and brain activity associated with anticipation of images from different categories during the period of 1000 to 2000 ms after the warning stimulus, which corresponds to the slow wave of anticipation. The participants did not become aware of the connection between warning stimuli and image categories, but significant differences in slow-wave brain activity (p <.05) between neutral and emotional paired conditions were observed (the effect of emotional modulation). Patients exhibited significantly higher emotional modulation in anterior regions of the brain (primarily, in the right hemisphere) associated with anticipation of images with people. The effect of emotional modulation associated with animal image anticipation was localized in the central-parietal or occipital regions, and hemispheric differences between the patient and control groups were observed. The results suggest that anticipation of social threat and other kinds of threat activates different mechanisms that can be selectively impaired in psychopathology.