Effects of transcranial magnetic stimulation on brain : studies in functional magnetic resonance imaging and brain proton magnetic resonance spectroscopy in patients with schizophrenia ; Effets de la stimulation magnétique transcrânienne sur le cerveau : études en imagerie fonctionnelle et spectroscopique chez des patients souffrant de schizophrénie

The understanding of the brain effects underlying the impact of repeated transcranial magnetic stimulation (rTMS) is a necessary a priori necessary concerning patients treatments. A posteriori, it also helps to understand the pathophysiological processes responsible for the clinical symptoms of mental disorders. Hither, we are interested in the effects of rTMS on the brain of patients with schizophrenia (SZ), through the two fundamental principles of cerebral functioning: segregation and functional integration. First, we have analyzed the effect of rTMS on the medial prefrontal cortex (MPFC) according to functional segregation in SZ with social cognition disorder. To do this we have developed an ecological and innovative social cognition paradigm for functional magnetic resonance imaging (fMRI). A prerequisite for longitudinal studies in fMRI is the reproducibility of the activation signal, we have then demonstrated the reliability of our paradigm between two sessions. Using this paradigm, we have studied the effect of rTMS on segregation from the variation of the BOLD signal and the levels of N-Acetyl Aspartate and glutamate. Then, we studied the impact of rTMS targeting the left temporal sulcus (STS) on auditory-verbal hallucinations (AVH) in terms of functional connectivity (functional integration). We have thus demonstrated the beneficial effect of rTMS on social cognition disorder and on AVH. Moreover, when the rTMS targets the STS, it does not seem to have an effect on the static functional connectivity within the listening language network. However, focused on the MPFC, it would increase the N-acetylaspartate concentration of SZ. The absence of the effect of the rTMS would rather illustrate different brain organization patterns of the SZ, due to inter-individual variability, suggesting that it would be in the future beneficial to determine optimal characteristics of stimulation on an individual basis in order to best modulate abnormal processes of the brain in schizophrenias. ; La compréhension des effets ...