Homotopic Coupling in Persons with Epilepsy using Movie-driven and Resting-state fMRI
Abstract
For the 30-40% of persons with epilepsy (PWE) with refractory epilepsy, seizure freedom following surgery is affected by the localization of the epileptogenic zone (EZ). However, functional abnormalities can exist at a distance from the EZ, which may contribute to variable outcomes after surgery. Considering epilepsy as a network disorder (Pittau & Vulliemoz, 2015), and evaluating functional coupling among homotopic brain areas, may help predict cognitive outcomes. Homotopic areas are well connected anatomically and undoubtedly work synchronously to generate cognition. We evaluated 22 persons with focal epilepsy and 24 neurologically healthy controls using fMRI at rest and while watching a brief and engaging audiovisual film clip. The Glasser parcellation (Glasser et al., 2016), a surface-based atlas that divides each hemisphere into 180 cortical regions and 22 functionally distinct sections, was applied and a baseline distribution of homotopic connectivity between pairs of regions and sections was established based on a subset of controls. Regional distribution of homotopic coupling activity was investigated as well as the relationship with performance on neuropsychological measures. We demonstrate the combined utility of resting-state and movie-driven fMRI for detecting homotopic functional coupling abnormalities in persons with refractory temporal lobe epilepsy. In addition, we find evidence of patient-specific and widespread abnormal homotopic functional coupling in PWE within and outside the temporal lobe. Finally, we show that the relationship between homotopic coupling at rest and performance on neuropsychological assessments shows group differences. Our findings supplement evidence of altered functional connectivity in epilepsy using resting-state fMRI and demonstrate how the engaged brain is altered in focal epilepsy.