Neurophysiological Basis of Emotional Face Perception and Working Memory Load in a Dual-Task MEG Study

Research on the neurophysiological effects of emotional face processing, working memory (WM) load, and their interaction in dual-tasks remains scarce. Therefore, we conducted a combined magnetoencephalography eye-tracking study with 47 participants. The dual-task temporally interleaved a facial emotion discrimination task with a visuo-spatial n-back task. Source-space cluster analyzes of event-related magnetic fields (ERFs) and oscillations revealed significant main effects of emotional expression and WM load. During emotion discrimination, enhanced ERFs for negative facial expressions located across the insula, ACC, and face-specific occipital regions suggest amplified emotion processing but also the recruitment of attentional control mechanisms. During the n-back phase, emotional faces did not affect evoked responses when they were task-irrelevant. Interaction trends in pupil dilation indicated that emotion-specific processing is diminished under high WM load. During the n-back phase, increased WM load reduced alpha and low beta oscillations in temporo- and parieto-occipital areas. In addition, reduced target fixations in the presence of negative facial distractors indicated a tendency toward emotion-specific interference. Furthermore, sustained increased WM load affected perceived valence, pupil size, and reaction time in both subtasks. A convergence of neurophysiological, physiological, and behavioural findings points to specific processing modes with greater resource depletion for negative expressions and high WM load in the dual-task. In conclusion, the study advanced our understanding of (a) circumstances under which emotional faces modulate ERFs in a dual-task, (b) mechanisms underlying emotion discrimination, (c) interaction effects of emotional expression and WM load in gaze behavior, as well as (d) how WM-related oscillatory alpha and beta power is affected by increasing load.