Default Mode Network Resting State Connectivity Derived from Task-based fMRI: A Validation Study in People with Epilepsy

Resting state functional connectivity can be measured using resting state functional MRI (fMRI) but also task-dependent fMRI in blocked designs. The latter has been demonstrated in healthy participants but not yet validated in clinical cohorts. Since functional connectivity of resting state networks (e.g. default mode network [DMN]) is altered in people with epilepsy and the impact of the disease on the quality of the ‘pseudo’ resting state data is unclear, we aimed to validate the method using a clinical fMRI in people with epilepsy. We compared functional connectivity derived from a standard resting state and rest periods of a clinical language fMRI (‘pseudo’ resting state) of 92 people with focal epilepsy. The ‘pseudo’ resting state fMRI was analyzed alongside the resting state fMRI across different aspects of functional connectivity: topography, within-network connectivity and second-level group comparisons. Therefore, we conducted independent component analyses (ICA), similarity-, regions of interest (ROI)-to-ROI- and second-level seed-based analyses. Results indicated similar ICA-derived topography of DMNs from both methods. Within-network connectivity of DMN regions also yielded comparable results. Seed-based analyses of left and right hippocampal connectivity in people with left and right temporal lobe epilepsy also revealed analogous results, with minor restrictions in right hippocampal connectivity. The ‘pseudo’ resting state method produces highly similar results to a standard resting state method in people with epilepsy across different aspects of functional connectivity. It is therefore an efficient approach to gain insights into functional connectivity networks in a clinical cohort without performing an additional resting state fMRI.