Healthy
Conditions
Brief summary
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
Detailed description
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.
Interventions
PROCEDURETranscranial alternative current stimulation (tACS) at alpha frequency
Single session of tACS
PROCEDURESham stimulation
Single session of tACS sham stimulation
Sponsors
Hôpital le Vinatier
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
TRIPLE (Subject, Investigator, Outcomes Assessor)
Masking description
Participants and experimenters (including α-tACS operator) will not be informed about the nature (active or placebo) of the stimulation they will receive
Intervention model description
Double-blind, placebo-controlled, randomized parallel arms study including 40 healthy participants who will receive active and placebo α-tACS
Eligibility
Sex/Gender
ALL
Age
18 Years to 45 Years
Healthy volunteers
Yes
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Area under the curve (AUC) of the cortisol secretion after the stress task. | 1 day | Samples of salivary cortisol will be repeatedly (10 occurences) collected during the experiment. The collection will take place before, during and after the stress task. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Effect of α-tACS on the molecular reactivity to stress | 1 day | The expression level of different proteins implicated in the intracellular communication channel after the couple cortisol-glucocorticoid receptor was formed (namely : NR3C1) will be assessed. A blood sample will be collected and the expression level of the relevant genes will be assessed by qPCR |
| Effect of α-tACS on the asymmetry of the alpha band (AFα) in stressed healthy subjects | 1 day | AFα refers to the average difference in alpha-band activity (typically8-13 Hz) between the left and right frontal areas (F3- F7 versus F4-F8, respectively). For a 5-minute block, AFα will be assessed by EEG recording while the participant is at resting state and only requested to alternatively open and close the eyes, according to a standardized procedure |
| Effect of α-tACS on the beta band in stressed healthy subjects | 1 day | The participant will have to complete the Kirby Delay Discounting Task (DDT). Subjects are presented with a series of hypothetical choices of amount of reinforcer to be had instantaneously, and a larger reinforcer available after a fixed delay. (For example : Would you prefer 37€ today or 80€ in 60 days? The outcome will be the change in the number of immediate choices between before and after the stress period (ΔDDT) express in percent |
| Effect of α-tACS on the cortisol awakening response in stressed healthy subjects | 4 days | Samples of morning salivary cortisol will be collected repeatedly (3 times) before experimental session (including the stress task and the tACS session). A last sample of morning salivary cortisol will be collected the following day |
| Effect of α-tACS on impulsivity in stressed healthy subjects | 1 day | The participant will have to complete the Kirby Delay Discounting Task (DDT). Subjects are presented with a series of hypothetical choices of amount of reinforcer to be had instantaneously, and a larger reinforcer available after a fixed delay. (For example : Would you prefer 37€ today or 80€ in 60 days?) The outcome will be the change in the number of immediate choices between before and after the stress period (ΔDDT) express in percent |
| Effect of α-tACS on time perception in stressed healthy subjects | 1 day | time perception refers to how the brain represents the temporal structure of events and of our environment. This ability can be assessed through different experimental designs. In this protocol, the participants will complete a time reproduction task, consisting in tapping at a defined frequency (1Hz) with a push-button. After a training phase (pressing the push-button while being guided), the participant will have to produce the same rhythm on his own. The outcome will be the mean difference between the reference interval (1s) and the time intervals executed by the participant, express in milliseconds |
| Effect of α-tACS on source monitoring in stressed healthy subjects | 1 day | Source monitoring refers to the cognitive processes involved in making attributions about the origins of mental experiences (for example : was this mental experience dreamt?, imagined?, really perceived? If this was perceived, was it produced by myself or by anybody else?. Two subtypes of source monitoring will be tested : the reality monitoring (RM) and the internal monitoring (IM). In each task the participant will be confronted with a list of words he/she will have to determine the source of. The outcome will be the proportion of false attributions, expressed in percent |
Countries
France
Outcome results
None listed