P100 in major depressive disorder and healthy controls: An emotion-processing task

Altered emotion processing, accompanied by cognitive bias leading to reduced positive reactivity and increased sensitivity to negative experiences, are core symptoms of Major Depressive Disorder (MDD), but the biological underpinnings are not yet resolved. Aim of the present study was to examine event-related P100 correlates of altered emotion processing in MDD compared to healthy control subjects (HCS).

Here, we assessed 87 MDD patients (age: 36.25 ± 13.38 years, 36 males, 51 females) and 100 HCS (age: 33.23 ± 11.63 years, 31 males, 69 females) using a 64-channel EEG system. P100 was regarded to amplitudes and latencies at left (P7/P5/P3/P07/P03/O1) and right (P8/P6/P4/PO8/PO4/O2) hemisphere electrodes in response to emotional stimuli differing in valence (positive/negative), arousal (low/high) and neutral target status (target/non-target).

HCS exhibited greater P100 amplitudes over the right hemisphere, whereas participants with MDD showed no hemispheric asymmetry. Amplitudes were higher in women than in men and in individuals with higher state anxiety scores. Unmedicated participants had higher amplitudes than those taking SSRIs or SNRIs, whereas combination therapy showed the highest amplitudes overall. SSRI use was associated with the shortest P100 latencies, while SNRIs were linked to the longest latencies.

No valence or arousal effects were observed. The data indicate right-hemispheric dominance in early visual processing among HCS, which was reduced in MDD subjects, suggesting diminished hemispheric lateralization in this group. Gender, anxiety level, and medication status significantly influenced P100 amplitude and latency, highlighting subtle alterations in early visual processing patterns in MDD.