The relationship between individual alpha-band activity and cognitive outcomes from repetitive Transcranial Magnetic...

Repetitive Transcranial Magnetic Stimulation (rTMS) is an effective treatment for Major Depressive Disorder (MDD) and can ameliorate cognitive control deficits. We examined electroencephalography (EEG) measures of cognition and mood at baseline and after rTMS treatment. We aimed to identify potential EEG correlates of cognitive control outcomes from rTMS treatment.

49 subjects with MDD received 30 sessions of rTMS administered to the left dorsolateral prefrontal cortex (DLPFC). Stroop Color Word Interference Task (Stroop task) was collected at their baseline session and after treatment in 31 of the 49 subjects, and EEG was recorded after the treatment course in 25 of these 31 subjects, with power in delta, theta, alpha, and beta bands as well as Individual Alpha Frequency (IAF) calculated. Changes in cognitive control and depressive symptom severity were assessed using the Stroop task and Inventory Depressive Symptomatology - Self Report (IDS-SR), respectively, from baseline (pre-rTMS treatment) through the end of rTMS session 30.

Subjects showed reduced depressive symptoms (p < 10^-10) and improved cognitive control (p < 0.05) following treatment, with no associations between improved mood and cognition. Higher alpha band relative power was significantly associated with greater accuracy on the Stroop task at baseline (p_adj = 0.006), and an increase in IAF following treatment was associated with improved task accuracy (p_adj = 0.01).

These findings indicate that improvements in cognitive control following rTMS for MDD are significantly associated with changes in alpha band activity. Baseline alpha activity may help identify those subjects who are most likely to show cognitive benefits from rTMS, and modulation of alpha-band activity may be associated with cognitive control enhancement.