No evidence for modulation of frontal brain activity asymmetry by a single session of EEG feedback

Recent studies suggest that frontal hemispheric asymmetry may underlie various mental health disorders, and frontal alpha asymmetry (FAA), which reflects cortical activity and inactivity between the left and right frontal lobes, could be a potential biomarker for these conditions. In this research, we investigated whether a single session of electroencephalogram (EEG) feedback (EF) can modulate and shift FAA. We designed a preregistered, triple-blind randomized-controlled trial to address this gap in the literature. Sixty-five healthy individuals (M _age = 24.55, SD _age = 7.63) were recruited for the experiment. First, we assessed baseline resting-state FAA over a 10-min period, consisting of 5 min each under eyes-open and eyes-closed conditions. Subsequently, participants were assigned to one of two 30-min-long EF protocols, designed to modulate cortical activity by enhancing activation in either the right or left frontal hemisphere. FAA was reassessed immediately after the completion of the feedback intervention. The results indicated that a single session of EF does not modulate FAA; therefore, it should be considered with caution regarding causal inferences. However, the absence of effects may also be attributed to the form of feedback used, as well as individual differences in baseline brain activity and neurocognitive/psychological profiles.