Study of the Correlation Between Cortical Excitability and Cytoarchitectonics of Prefrontal Cortex in Healthy Adult Participants, Using Transcranial Magnetic Stimulation Coupled to EEG and High-field MRI

Repeated transcranial magnetic stimulation (rTMS) is mainly used to treat mood disorders by addressing differences in brain function, particularly in the dorsolateral prefrontal cortex (DLPFC), which affects emotions and executive functions. The therapy aims to enhance the left DLPFC or suppress the right. It has been approved for severe major depression in several countries (Canada and Israel since 2002, USA since 2008) and is in the process of being validated in Europe but is not yet reimbursed in France. due to variable results from one study to another and lack of standardization issues. In a previous study, by recording electroencephalographic (EEG) rhythms before and after rTMS treatment of the DLPFC, the investigators showed on a small cohort of patients (n=17) with major or bipolar depression, that the responder patients showed higher EEG theta rhythms in the DLPFC but also and especially in parietal regions. This suggests that the DLPFC is part of the fronto-parietal central executive network (CEN), which is important for working memory and cognitive control. The CEN is not well connected in severe resistant depression, possibly leading to negative emotional bias. The rTMS cure of DLPFC can be interpreted as improving depressive symptoms through the normalization of the CEN by increasing DLPFC excitability and its downward connectivity. However experimental and clinical evidence for this mechanism, among others, is still to be demonstrated, and remission rates of rTMS from DLPFC in drug-resistant depression are still low (20-40%). To improve these response rates to rTMS in DLPFC, it is essential to continue research aimed at improving clinical practices through a better knowledge of the functional neuroanatomy and mechanisms of action of rTMS. This will require the definition of biomarkers allowing in particular to better target the DLPFC, this structure beeing indeed relatively poorly defined on the neuroanatomical level (large portion of the medial fron