Browsing by Author "Croset, Léa"

Major Depressive Disorder (MDD) is a prevalent health issue worldwide, yet one third of patients are unresponsive to first-line treatment. Repetitive Transcranial Magnetic Stimulation (rTMS) is a promising alternative treatment and better understanding of the neural network impairments associated with MDD could significantly improve its efficacy. Recent research has identified a ‘depression network’ involving key brain regions, suggesting that MDD symptoms arise from functional connectivity impairments within this network. This thesis aims to map the activity and functional connectivity of six bilateral regions of interest (ROIs) implicated in MDD: dorsolateral prefrontal cortex (dlPFC), dorsomedial prefrontal cortex (dmPFC), ventromedial prefrontal cortex (vmPFC), inferior frontal gyrus (IFG), intraparietal sulci (IPS) and pre-supplementary motor area (pre-SMA). The intention is to describe biomarkers of depression and map the depression network to identify connectivity impairments between these cortical sites. Literature on these ROIs was reviewed and rsEEG data from 24 MDD patients and 9 healthy controls was collected to analyze the activity and functional connectivity of selected ROIs. Our results suggest that MDD involves widespread connectivity impairment including in regions that have not previously been included in the research on depression, such as IFG and IPS. Most ROIs showed trends of reduced activity in delta, theta, alpha and beta bands. The effects were most noticeable in the theta band, especially in the IFG, dmPFC, and dlPFC. However, the functional connectivity impairments were more prominent and significant, particularly in the beta and alpha bands. Notably, the IPS and vmPFC stood out as key nodes with the most dysfunctional connections in MDD. These findings support the idea of a depression network characterized by connectivity abnormalities rather than localized activity impairments. This study emphasizes the importance of a network-based approach in understanding MDD. The search for biomarkers as well as novel stimulation targets should consider regions beyond the traditional dlPFC or the frontal cortex, to include regions such as IPS, IFG and vmPFC.