La représentation auditive motrice reflétée par la négativité de discordance chez l’enfant
présentant un trouble du spectre de l’autisme

Mirror-neuron system (NMS) has been suggested to underlie action understanding, which is believed to be involved in higher social functions such as empathy and imitation. Numerous studies have also provided indirect evidence supporting the existence of a MNS in the human brain using functional magnetic resonance imaging, transcranial magnetic stimulation, magnetoenceophalography and electroencephalography (EEG). As evidence relating MNS function with social cognition accumulated, its dysfunction was proposed to underlie social impairments in Autism Spectrum Disorder (ASD). Although some studies have reported structural and/or functional data supporting this hypothesis, it remains controversial. Indeed, the techniques used to probe MNS activity often require the participant to understand the task, display sustained attention and present spared visual cognitive functions, which could be altered in ASD population. This, in turn, could partly explain differences in MNS activity found between invididuals with ASD and neurotypical participants. The auditory mismatch negativity (MMN) protocol has recently been proposed as a viable tool to assess MNS activity using action-related sounds. This relatively short oddball paradigm does not require visual, attentional or language skills and can be performed with minimal electrode installation (minimal use of 4 electrodes). This action-related MMN may therefore be well-suited to investigate MNS function in very young children or populations with mental disabilities, such as ASD. The first article of this thesis assessed the convergent validity of the action-related MMN protocol with a mu rhythm suppression paradigm, which is the most commonly used EEG measure of MNS activity. To do so, both protocols were consecutively administered in healthy adults in the same experimental session. While both techniques successfully 4 modulated the fronto-central and central brain regions using action-related stimuli, they did not correlate significantly. This suggests that the two techniques may not probe the same aspects of MNS function. The second article aimed at investigating MNS activity in children with ASD using the action-related MMN protocol. Data were compared to age-matched typically developing children. We show that children with ASD present an opposite pattern to that of control children : whereas MMN latencies are shorter for action-related sounds compared to control sounds in neurotypical children, the opposite pattern is observed in children with ASD. Furthermore, although the two groups present different response patterns with regards to action-related sounds, they repond similarly to control sounds. For amplitude measurements, children with ASD display reduced amplitude to action-related sounds produced by the mouth compared to neurotypical children. In summary, this thesis aimed at determining whether and action-related MMN protocol could be used to measure MNS activity in neurotypical adults and children, as well as in ASD children. The action-related MMN could potentially be used as a biological biomarker of ASD pending further studies.

Keyphrases: neuroanatomie, Autistic Spectrum Disorder, neurodevelopmental disorders, adults, child development, neuropsychological assessment, social cognition, perception of auditory-motor representations, electoencephalography assessment, psychophysiology, neuroanatomy