Effects of Alpha Transcranial Alternating Current Stimulation on Stress Reactivity and Decision Making: A Randomized...

Evidence suggests that alpha-band power plays a crucial role in stress response and decision making (DM). Transcranial alternating current stimulation (tACS) is a noninvasive brain stimulation technique capable of modulating brain oscillations in a frequency-specific manner. In this study, we investigated whether alpha tACS (α-tACS), delivered to healthy individuals while they experienced an acute stress situation, would influence biological stress responses and DM performance.

In a double-blind, sham-controlled study, 38 healthy individuals were randomly assigned to receive either α-tACS (2 mA, 30 min, 10 Hz; n = 19) or sham stimulation (n = 19) on the prefrontal cortex (PFC) during stress exposure. Salivary cortisol reactivity was measured repeatedly to assess the biological stress response, DM was assessed with the delay discounting task.

Compared with sham (mean area under the curve with respect to ground [AUCg] = 76.4, SD = 29.63), α-tACS (mean AUCg = 103.4, SD = 49.08) significantly increased stress-induced cortisol release (p = .048, Cohen's d = 0.342). α-tACS also significantly decreased discounting rates following stress whereas no effect was observed in the sham condition.

Although some limitations, such as the absence of electroencephalography recordings and high variability in outcomes should be considered, these findings suggest that modulation of prefrontal alpha oscillations via tACS may reduce top-down regulatory control from the PFC, resulting in an enhanced biological stress response. This effect was accompanied by alterations in DM processes, supporting a functional relationship between frontal alpha activity, stress reactivity, and DM. These mechanisms offer promising therapeutic prospects for stress-related disorders like posttraumatic stress disorder, which involve altered alpha-band oscillations and blunted cortisol reactivity.