Autism Spectrum Disorders (ASD) are neuro-developmental disorders presumably related to neural circuit alterations. The symptoms, that start very early in development and persist through adulthood, can lead to severe handicap. Even though a wide variety of clinical severity exists, difficulties in social interactions are a core feature of ASD. These difficulties are characterized by social perception abnormalities, manifested mainly through abnormal eye contact. Such abnormalities have been largely confirmed in the last decade by eye-tracking studies, which allow objective and quantitative investigation of gaze behaviour. Studies with adults and children with ASD during visualization of social scene have shown a lack of preference for socially relevant information, mainly faces and eyes.

In the typically developing brain, socially relevant information is processed within a specific network, called the social brain. Functional MRI (fMRI) activation studies have shown the implication of a key region of the social brain, namely the superior temporal sulcus (STS), is in processing social information, ranging from the perception of eyes, faces and voices to the more complex processes of social cognition. Over the last decades, brain imaging studies investigating the neuro basis of ASD have consistently described anatomical and functional abnormalities within the social brain, particularly within the STS Currently there are important limitations in the therapeutic interventions available for ASD. Pharmacological treatments are only indicated for psychiatric comorbidity and has no impact on ASD core manifestations. Behavioural interventions, on the other hand, are generally expensive, time-consuming and have modest results. In more recent years non-invasive neuromodulation techniques, such as Transcranial Magnetic Stimulation (TMS), have raised hope as effective tool to address ASD core manifestations. Indeed, modulating the neural activity of STS with an impact on social perception opens new therapeutic perspectives in ASD. The effect of TMS on social behaviour has been recently showed by a study from our lab. Following an inhibition of the right STS by inhibitory TMS, healthy volunteers look less at the eyes of the characters during the visualization of social scenes.

In this context, the main objective of this study is to investigate the effect of repetitive session of TMS applied to the STS on social perception in patients with ASD. In addition, the investigators aim to research the impact of putative changes in social perception in broader social behaviour using clinical scales. Finally, the investigators aim to research putative changes in brain functioning at rest by measuring rest cerebral blood flow using Arterial Spin Labeling (ASL)-MRI before and after TMS. This is a double-blind, randomized, placebo-controlled therapeutic trial, ultimately aiming to improve broader social behaviour.

For that purpose, the investigators will include in the present study 20 participants with non-syndromic ASD aged from 18 to 25 years old. Social perception will be measured using an eye-tracking during passive visualization of social stimuli. All patients will undergo an MRI for neuronavigation purposes and to obtain rest cerebral blood flow measures using arterial spin labelling MRI sequence, as well as clinical scales to evaluate their global social behavior: clinical global impressions (CGI), "évaluation des comportements autistiques revise" (ECA-R) and autism behavior checklist (ABC). The 20 patients will be automatically randomized in the active TMS arm (n = 10), or in the placebo arm (n = 10). Patients will undergo 10 sessions of TMS applied to the posterior part of the right superior STS, from Monday to Friday for two consecutive weeks. Following the 10 sessions, evaluations will be performed: 5 days, 1 month and 3 months after the end of the treatment.

The investigators expect that stimulation of the posterior part of the STS, a region shown to be strongly implicated in processing social information, mainly from the eyes, would lead to an increase in eye-gaze perception and thus promote access to social cues necessary for adapted broader social behavior. If so, TMS could be further considered as an alternative therapeutical intervention in ASD.