Transcranial Magnetic Stimulation (rTMS) and Autism.

Autism is characterized by severe impairments in verbal and non verbal communication and in social interactions. Results from cerebral imaging studies have suggested that abnormalities located on the superior temporal Sulcus (STS) level would be implicated in social impairments in autism. This abnormalities are both anatomical and functional: 1) rest hypoperfusion detected by positron emission tomography (PET); 2) abnormal activation during social tasks (fMRI) and 3) structural abnormalities shown on anatomical MRI. The STS is implicated in social cognition in normal subjects. Our hypothesis is that these anatomo-functional abnormalities would appear very early in brain development and could be one of the first steps in the cascade of neuronal dysfunction in autism. Transcranial Magnetic Stimulation (rTMS) is a technique which is used in cognitive neuroscience research as well as in therapeutic approaches in certain neurological and psychiatry diseases. It consists on applying a magnetic impulse on the brain trough the scalp in a non-invasive and painless by placing a coil on the surface of the head. This magnetic fields induce an electrical field which modifies activity of those neurons inside the magnetic field and induce an electrophysiological change in the target area. This process allows a non-invasive interaction with the human brain in action during focal stimulations. In cognitive neuroscience research, we are interested in the modifications caused by rTMS in cognitive performances in order to better precise the functional role of the target region. The intensity and the frequency of the impulse can be controlled (frequency <1 Hz = inhibitory effect ; frequency > 3 Hz = excitatory effect). The functional characteristics of a given region and it's eventual dysfunctions may be identified thank to the abnormalities in reactivity and cortical connectivity. The goal of this project is to study inhibitory and excitatory effects of rTMS applied to the STS in healthy controls and patients with autism. This effect will be measured by two main parameters of social cognition: 1) visual perception of social scenes, measured by eye-tracking methodology; 2) auditory perception of human voice. We will study 50 healthy voluntaries controls and 50 patients with a non-syndromic autism (18 to 25 years old; IQ > 60), diagnosed by DSM-IV and ADI-R. All participants will undergo an structural MRI and a rTMS session on the STS. In both cases, the STS will be localised based on the structural MRI. The total duration of the rTMS session is about two hours. All data will be analysed by the adapted statistical methods. This study will allow a better understanding of the role of STS in social cognition in healthy subjects as well as it's implication in the social impairments which characterize autism. Finally, the rTMS may become, in a near future, a innovative therapeutic strategy in autism.