Effects of alpha-transcranial Alternating Current Stimulation on stress reactivity and decision making

Evidence suggests that alpha band power plays a crucial role in stress response and decision making. 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, delivered to healthy individuals while they experienced an acute stress situation, would influence biological stress responses and decision-making 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) over the prefrontal cortex during stress exposure. Salivary cortisol reactivity was measured repeatedly to assess the biological stress response. Compared to sham (mean AUCg = 76.4, Standard Deviation 29.63), α-tACS (mean AUCg = 103.4, SD = 49.08) significantly increased stress-induced cortisol release (p = 0.048, 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 EEG recordings and high variability in outcomes, should be taken into account, these findings suggest that modulation of prefrontal α-oscillations via tACS may reduce top-down regulatory control from the prefrontal cortex, resulting in an enhanced biological stress response. This effect was accompanied by alterations in decision-making processes, supporting a functional relationship between frontal alpha activity, stress reactivity, and decision-making. These mechanisms offer promising therapeutic prospects for stress-related disorders like PTSD, which involve altered α-band oscillations and blunted cortisol reactivity.