Étude de la connectivité cérébrale dans l’autisme adulte par l’analyse de la cohérence de l’EEG à l’éveil et en sommeil paradoxal

Autism is a neurodevelopmental disorder of unknown etiology. Converging neuroimaging data in the last years suggest that alteration in communication between regions within the autistic brain is governed by the cognitive functions associated with these regions rather than by their sheer physical distance. Some theoretical models were postulated to explain these observations, without unifying all of them. Results of the literature on this matter are often heterogeneous and several methodological disparities exist between the studies, moments and conditions of recording, and the heterogeneousness of the populations often presenting multiple comorbidity limit their interpretation. The objective of this thesis was to compare the brain connectivity of adult participants with autism (18-35 years old) without intellectual deficiency to neurotypical participants, by means of a measurement tool offering a complementary vision to the neuroimaging: the electroencephalography (EEG) coherence. The EEG coherence is a method which evaluates the synchronization in time between pairs of electrod signals recorded at different neocortical sites and constitutes essentially a measure of the functional connectivity between cortical regions. In this thesis, we exercised a rigorous control to make sure that our results are not influenced by staggering variables and we recorded our participants during REM sleep (first paper) and during two spontaneous moments of activation while the cortex is activated but not requested, waking resting state with closed eyes, during evening and morning (second paper). We also estimated the correlation between the significant EEG coherence results observed during waking state in the autism group, with their clinical symptoms on the behavioural questionnaires ADI-R and ADOS-G. Several of the significant results obtained in this research were common to all studied moments of brain activation. Indeed, the observation of a superior EEG coherence involving the left visual area during the waking states as well as during the REM sleep confirms a certain facilitation of the visual regions in the autistic group compared to the control group. The presence of a left frontal coherence decreased in the participants with autism compared to the neurotypicals supports anatomical and clinical observations suggesting a deficit of the cognitive functions involved in this region. The significantly decreased frontal inter-hemispheric coherence in the autistic group compared to the controls in the morning waking recording supports an alteration in the callosal fibers which could be modulated by developmental changes associated with age. Finally, significant correlations involving the number of clinical symptoms and the EEG coherence of autistic participants could suggest that alteration of connectivity has an impact on the diurnal behavior and the symptomatology. Thus the results of this thesis add to the scientific knowledge concerning the dynamics of cerebral connectivity in autism and support the hypothesis of an atypical brain organization, distinct from neurotypicals, both in the waking as in the sleep states.

Keyphrases: autism, brain  connectivity, polysomnography, sleep