Abstracts

Rationale: Mapping brain networks allows insight into the brain's functional architecture and physiology and help to better understand and treat TLE. Diffuse optical tomography (DOT) is an emerging functional neuroimaging technique that can simultaneously map both oxy- and deoxyhemoglobin with high temporal resolution. The aim of this study is to reveal directed interactions of activated brain areas in TLE using both the DOT findings and the effective connectivity techniques, such as Granger causality. Methods: We performed the simultaneously EEG and optical recordings in rats with seizures. Granger causality analysis based on activity-evoked optical change measurements including oxy- and deoxyhemoglobin time courses, is implemented to build a plausible network between different brain regions of interest (ROI). Results: With the recovered blood volume and blood oxygen parameters, the three-dimensional DOT is able to localize the epileptic foci. The hemodynamic parameters in ROIs are then employed to generate the effective connectivity network, which exploits the time-frequency representation of neural time series to manifest causal relationship in different frequency bands, as well as at different time instants. The simultaneous EEG recordings are also processed to investigate the neurovascular coupling and help interpret the built network. Conclusions: DOT is gaining acceptable as a technique particularly suitable for routine follow-up in children and unconscious epilepsy patients since it utilizes the noninvasive light to capture the neurovascular and neurometabolic parameters. The Granger causality analysis based on the DOT findings is able to reveal the directed influences between different brain areas. Compared with fMRI, the comprehensive hemoglobin contrasts of DOT enable innovative studies of the biophysical origin of the effective connectivity signal in TLE.