Investigation of functional brain connectivity patterns in temporal lobe epilepsy

Abstract

In this study, functional connectivity using both Pearson and partial correla tion coe cients and inter-subject variability were investigated in resting state func tional resonance imaging (rs-fMRI) scans that belong to healthy and temporal lobe epileptic (TLE) patient populations. The main purpose of this thesis is to reveal the discrepancies between the healthy population and the patients with TLE in terms of functional connectivity revealing the temporal dependency among di erent brain re gions. According to inter-subject variability results, TLE population exhibited higher inter-subject variability in frontoparietal control, default mode, dorsal/ventral atten tion, visual, limbic and somatomotor networks in line with the broad seizure onset and propagation pathway. We mostly found a signi cantly reduced functional connectivity in bilateral frontoparietal control, somatomotor, default mode and ventral attention networks with an implication of dysfunctioning in attention, long/short term memory, cognitive functioning and consciousness in patients with TLE as a result of 17-network parcellation. We also found a decreased functional connectivity between/within the networks of the frontoparietal control, the default mode and the ventral attention im plying that these three networks as well show a variability, although to a lesser extent. This result signi es these networks are severely deteriorated in patients with TLE. On the other hand, to compute the direct functional connectivity among di erent brain regions, partial correlation coe cients estimation is used. In doing so, we took advan tage of Random Matrix Theory to well approximate the partial correlations, by virtue of, the inverse covariance matrices. As a result, the bilateral homologous structures in dorsal/ventral attention, frontoparietal control and default mode networks were also decreased in patient population con rming our results using Pearson's corelation coef- cients.|Keywords : Resting State fMRI, Functional Connectivity, Temporal Lobe Epilepsy.