Glutaminergic Transmission in Autism : Molecular Imaging Exploration

Inclusion Criteria: * Male * Between 18 years-old and 45 years-old * Informed, written consent obtained from patient or his representant * Subject with an affiliation to French social security * For autistic patient : patient with diagnosis of ASD (Autistic Spectrum Disorders) following DSM-IV or DSM-5 criteria with recommended tools (ADI-R and/or ADOS) * For FXS patient : diagnosis of FXS and confirmation of total mutation of FMR1 Exclusion Criteria: * Contraindications to MRI * Excessive use of alcohol or drug, or addiction to alcohol or drug during last 6 months * Any unstable or uncontrolled disease, clinically significant * Participation to an other experimental protocol with drug or irradiant exam * Person under exclusion period because of previous participation to an other experimental protocol * Person under temporary guardianship * Forbidden treatments : any psychotropic treatment for 4 last weeks before PET exam and changing durably glutaminergic transmission directly or undirectly * For healthy subjects : adult under guardianship, medical history of central nervous system disease, medical history of attention deficit hyperactivity disorder, past or present psychiatric or neurologic disorder (MINI DSM-IV)