Inclusion criteria :  OSAS patients  severe OSAS with an Apnea-Hypopnea Index (AHI) > 30/h without CPAP treatment  Non-OSAS patients  absence of OSAS (AHI < 15/h and absence of excessive daytime sleepiness with Epworth score <11)  Non-inclusion criteria :  < 18 years old >75 years old left-handed BMI> 40 kg/m² another sleep disorder central component of sleep apnea syndrome (central apnea index> 5 / h) current or past neurological pathology respiratory pathology (obstructive ventilatory disorder, restrictive ventilatory disorder, hypercapnia) MRI contraindication (metallic foreign body, claustrophobia, pregnant woman, etc.) taking drugs that can modify the BOLD signal on MRI (psychotropic drugs, vasodilators, vasoconstrictors, etc.), uncorrected sensory impairment (vision or hearing) protected by law.  Exclusion criteria :  pregnant woman according to the positive beta-hCG test result left-handed following the laterality questionnaire  MINI results showing:  a current mood episode a current disorder of the use of psychoactive substances or in the last 6 months (excluding tobacco) an eating disorder a diagnosis of bipolar disorder, current or past schizophrenia