The knowledge on brain mechanisms of psychopathology can be very useful for the diagnosis and treatment of patients.

Patients with major depressive disorder (MDD) show attention bias to the negative emotional stimuli. Automatic (unconscious) emotional processing in such patients may become a prospective biomarker for depression.

We aimed at studying the EEG-correlates of unconscious expectation of angry human faces in MDD patients compared to healthy controls.

128-channel EEG was recorded in MDD (23 females and 7 males) and in healthy volunteers (22 females and 8 males) while they categorized pictures as humans or animals. Half of the pictures were neutral and half were showing the faces of angry humans or animals. The pictures were preceded by cues (one for each category), which meaning was not explained to the participants. We performed the wavelet analysis on EEG recorded during the face expectation period: 1000–2000 ms from the cue onset.

We found the emotional modulation (EM) in EEG rhythms during the expectation of angry vs. neutral faces in both groups. Statistical comparison of the spectral power using 2 × 2 factorial design showed that the EM differences (P < 0.05) between the groups were in the left parietal locations in 9 Hz and in 16–18 Hz, in the right parietal locations in 27–28 Hz, and in the right frontal area in 30–31 Hz.

The unconscious expectation of angry vs. neutral faces resulted in EM differences between the MDD and healthy controls in the right frontal and bilateral parietal areas mostly in beta and gamma ranges.

The authors have not supplied their declaration of competing interest.