Cortical activation asymmetry

Preliminary evidence that daily changes in frontal alpha asymmetry correlate with changes in affect in therapy sessions

Frontal EEG alpha asymmetry was recorded from five depressed outpatients during early EEG biofeedback sessions. Mood was assessed prior to and after each session, and affect change scores were also derived by subtracting pre-session from post-session scores. Alpha magnitude was obtained via Fast Fourier Transforms. All scores (EEG alpha asymmetry and affect) were converted to deviation scores by subtracting each patient's daily score from that patient's mean across all available sessions for that patient. Pearson correlations were then computed between asymmetry and affect scores using the deviation scores combined over patients. There was little evidence of correlation between day-to-day asymmetry score and any single affect score. Strong correlations were obtained, however, between asymmetry score and affect change score and, in particular, between asymmetry score and change in positive affect.