The Myelex study is a fundamental research study that aims to better understand how the brain functions and develops. The objective of this study is to better understand the role of myelin, a sheath that surrounds nerve fibers and determines the speed of information propagation in the brain, in cognitive functioning during development in adolescents and young adults. investigator use Magnetic Resonance Imaging (MRI) because this method allows us to study the anatomy and functioning of the brain in a non-invasive (no injection) and painless manner. investigator focus on cognitive control, a set of cognitive functions in the prefrontal cortex, at the front of the brain, that enable the use of the best strategies on a case-by-case basis to solve problems effectively. These functions are closely associated with academic and professional success and develop late, continuing until early adulthood. The goal of this project is simple: to measure the myelin of nerve fibers using MRI and to evaluate the link with the development of cognitive control. Each participant will undergo an MRI examination and cognitive assessments. The study takes place at the Clinical Research Center of GHU Paris and lasts a total of 3.5 hours, including reception, setup, MRI recording, and the completion of a series of cognitive tasks.

Selection visit

• Call for participants for pre-selection

• Sending of information forms by mail

• Making an appointment for the inclusion visit Inclusion visit at GHU Paris.

• Information on the modalities, constraints and foreseeable risks of the study

• Collection of informed consent

• Verification of inclusion/non-inclusion criteria

• Clinical examination: o Verification of medical history and drug treatments

  • Psychiatric pathology in first-degree relatives
  • Consumption of toxic substances (nicotine, alcohol, cannabis, etc.)
  • Manual lateralization will be assessed by the score on the Edinburgh questionnaire (Oldfield, 1971)
  • Blood sample to measure pubertal hormones (testosterone, estradiol and progesterone levels)

• Collection of main medical history and concomitant treatments

• Explanation of study procedures

• MRI examination

• Cognitive assessment

Inclusion Criteria:

• Male or female; Subject aged 10 to 25 years; Right-handed preference; Subject, or legal representative, who has given consent to participate; Native language: French; Subject affiliated with a social security system; Having signed their consent to participate (and their legal representative if applicable), subjects and parents have read the information letter and given their free and informed consent. In cases where only one parent gives consent (for minors), this must be justified (such as no contact with the other parent for over a year).

Exclusion Criteria:

• Not corresponding to the targeted age range;
• Subject with contraindications to an MRI examination (pacemaker or neurosensory stimulator or implantable defibrillator, cochlear implants, ferromagnetic foreign bodies in the eyes or brain near neural structures, metal prostheses, patient agitation: non-cooperative or agitated patients, minors, claustrophobic subjects, pregnant women, ventriculoperitoneal neurosurgical shunt valves, dental braces);
• Subject with chronic alcohol or drug use;
• Abuse or dependence on substances (except nicotine) or toxic substances for more than 5 years or having led to comas (overdoses);
• Subject with sudden-onset cognitive disorders that could indicate a stroke; a history of head trauma with loss of consciousness for more than 1 hour, or encephalitis;
• Subject with chronic neurological, psychiatric, endocrine, hepatic, or infectious conditions;
• Subject with a history of major illness (diabetes, chronic lung disease, severe cardiac, metabolic, hematological, endocrine, or immunological disorder, cancer);
• Subject on medication: taking medications likely to interfere with brain imaging measurements (psychotropics, anxiolytic hypnotics, neuroleptics, anti-Parkinsonians, benzodiazepines, steroidal anti-inflammatories, antiepileptics, central analgesics, and muscle relaxants);
• Color blindness;
• Inability to comply with the study for geographical or psychiatric reasons;
• Tattoo incompatible with MRI;
• Cerebral palsy;
• Fine motor skills disorder;
• Pregnant women at the time of inclusion;
• Adult subjects under legal protection or unable to give consent (article L.1121-8 of the French Public Health Code) (under guardianship or curatorship);
• Children and parents under legal protection measures

Healthy adolescent and adult volunteers aged 10 to 25 years with no contraindications for an MRI examination.