Effect of Transcranial Alternative Current Stimulation at Alpha Frequency (α-tACS) on Stressed Healthy Subjects

Biological, Neuropsychological and Electrophysiological Effect of Transcranial Alternative Current Stimulation at Alpha Frequency (α-tACS) on Stressed Healthy Subjects

stress. Notably, several studies reported that stress could alter impulsivity, source monitoring, and time perception.

Several mechanisms are involved in the response to a stress factor, among them the hypothalamic-pituitary-adrenal (HPA) axis. The cortisol reactivity (it means the cortisol secretion after the exposure to a standardized stress factor) is a reliable tool to assess the function of HPA. Cortisol secretion is bidirectionally influenced by the prefrontal cortex (PFC), which is involved in the expression and regulation of stress as well. The asymmetry of the alpha band (AFα) is a well known electrophysiological parameter to assess the function of PFC. More precisely, AFα is arising a growing interest, as it is believed to be correlated with the cortisol reactivity. Modifying this asymmetry could influence the stress response.

Transcranial Alternating Current Stimulation (tACS) consists in delivering a sinusoidal alternating current between two electrodes placed on the scalp at a predefined frequency. Previous studious reported that tACS, if delivered at the alpha frequency, increased the alpha band in the stimulated areas

The study will focus on the effect of tACS at alpha frequency (α-tACS), delivered on the dorsolateral prefrontal cortex, on the response to a stress factor.

In this study, while receiving a single α-tACS session, the participants will complete a standardized stress test combining cognitive stress (mental calculation) and physical stress (cold pressure): the Maastricht Acute Stress Test. The main objective aims at assessing the effect of a single session of tACS at alpha frequency, delivered on the dorsolateral prefrontal cortex, on the cortisol reactivity in healthy stressed subjects. In that study, the influence of α-tACS on other biological ; electrophysiological, neuropsychological parameters relevant for the stress response will be assessed also.

Inclusion Criteria:

• Right-handed Men and Women aged between 18 and 45
• If woman, hormonal contraception required
• Having given their written informed consent
• Affiliated with a social security scheme
• French speakers and readers

Exclusion Criteria:

• Contraindication to the exposure to exposure to tACS
• Current psychiatric disorder as classified in the DSM-5
• Regular intake of any psychotropic drug or Beta Blocker
• Recent exposure to a traumatic event
• Any debilitating condition making the experimental procedure not feasible
• Pregnancy