Brain Imaging Lecture - Prof Jorge Riera - Understanding BOLD signal genesis in focal epilepsy
Prof Jorge Riera, PhD - Biomedical Engineering - Florida International University (Miami)
Understanding BOLD signal genesis in focal epilepsy
Abstract - Blood-oxygen-level dependent (BOLD) activation evoked by interictal epileptiform discharges (IEDs) has been employed as a clinical biomarker to identify the seizure-onset zones in patients with intractable focal epilepsy. However, the existence of BOLD deactivations in certain brain regions confounds the analysis and interpretation of the BOLD signals, thereby reducing the value of EEG-fMRI in the process of planning an epilepsy surgery. In this study, we investigated the causal relationships between the IED-related BOLD activation and deactivation in a preclinical rat model of focal cortical dysplasia, as well as explored their relationships with alterations in the resting state networks (RSNs). Also, we employed a metabolically-coupled balloon model to evaluate the neuro-vascular/metabolic coupling in this preclinical model. The model included modulatory effects of changes in tissue oxygenation, capillary dynamics and variable O2 extraction fraction incorporated in. Using intracranial recordings (LFP/MUA, CBF, CBV, [Deoxy-Hb]) from epileptogenic regions, we found that: a) the most significant contribution to the CBF responses comes from high-oscillatory neuronal activities and b) crucial parameters of the biophysical model are significantly different between epileptic and normal cortices. Finally, histological studies provided us insights about the cellular basis underlying such abnormalities in the neuro-vascular/metabolic coupling, paving the ways for a future therapeutic control using optogenetics. We discuss these results in terms of recent findings from our group about vessel network changes in pedriatic epilepsy.
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