Transcranial Electrical Stimulation (TCES) / Cerebral Blood Flow (CBF) / Xenon Under Computerized Tomography (Xe/CT)

Direct stimulation of the cerebral cortex induces an increase in cerebral blood flow. Although this information is known, it has never been documented during Transcranial Cerebral Electrical Stimulation (TCES), which is a non invasive technique. It is used to modulate the opiate endogenous system, mainly in opioid users but no cerebral blood flow mapping of the anatomic regions involved in this modulation of the opiate system under electrical stimulation has been performed in functional Computerized Tomography.

* Principal Objective : To compare the increase in mean cerebral blood flow in a group of defined zones (the thalamus, anterior cingulate gyrus, the insula, periacqueductal region of the brain stem,the frontal lobes, the striatum and limbic system) in healthy volunteers stimulated or not stimulated by TCES.
* Secondary Objective : Description of cerebral blood flow variations in the different zones in order to map electrostimulated areas.
* Study design : An experimental, randomized, double-blind, single-centre trial with 2 groups, a study group (stimulated by TCES) and a control group (not stimulated).
* Inclusion criteria : Participants free of any known neurological or psychiatric disorder; participants not under treatment particularly with opioids, analgesics or medication containing codeine or morphine for at least a month; participants aged between 18 and 65 having signed a written informed consent ; participants having accepted to be registered on the national eligibility list for subjects participating in a trial without direct individual benefit, and covered by an insurance policy.
* Exclusion criteria : Participation in two different study trials without direct individual benefit at the same time. Contraindications to Computerized Tomography. Subjects diagnosed clinically with a Neurological or Psychiatric disorder; Subjects who have been under analgesics or morphine agonists for less than a month; Pregnant or breastfeeding mothers and women without an adequate contraception. Drug addicts or persons under tutelage.
* Study plan: Study group: Xe/CT and transcranial electrostimulation / Control group : Xe/CT
* Principal Criterion of Judgement: difference in mean cerebral blood flow between the study group(stimulated) and the control group (not stimulated).
* Secondary Criteria of Judgement : Difference in mean cerebral blood flow region per region (thalamus, anterior cingulate gyrus, insula, periacqueductal region of the brain stem, the frontal lobes, the striatum and limbic system).
* Number of subjects : 40
* Duration of subject participation in study : 2 H 30

Eligibility Criteria:
Inclusion Criteria:

* Participants free of any known neurological or psychiatric disorder
* participants not under treatment particularly with opioids, analgesics or medication containing codeine or morphine for at least a month
* 18 and 65
* informed consent signed

Exclusion Criteria:

* Contraindications to Computerized Tomography
* Subjects diagnosed clinically with a Neurological or Psychiatric disorder
* Subjects who have been under analgesics or morphine agonists for less than a month
* Pregnant or breastfeeding mothers and women without an adequate contraception
* Drug addicts
* persons under tutelage