Determining the Role of Synchrony Dynamics in Epileptic Brain Networks

Abstract

Epilepsy is a chronic neurological disorder characterized by recurrent, spontaneous, paroxysmal neural discharges called seizures (Mogul and Drongelen, Annu. Rev. Biomed. Eng. 16, 483–504, 2014). Synchronous electrophysiological activity between neuronal networks underlies essential motor and cognitive processes in normal brain function (Ward, Trends Cogn. Sci. 7, 553–559, 2003). However, synchrony levels can be altered in several neurological disorders such as epilepsy. This chapter reports on using a nontraditional nonlinear, adaptive, analytical methodology to investigate the dynamical evolution of synchrony in neuronal electrophysiology of epilepsy patients with temporal and frontal lobe epilepsy. Decreased multisite brain synchrony is observed at seizure onset in both types of focal epilepsy studied. In contrast, elevated synchrony at seizure termination is found in both human and rat epilepsy. When deep brain stimulation (DBS) is applied to epileptic rats that mirrored the endogenous synchrony dynamic specific to each subject that is observed at natural seizure termination, seizures rapidly terminated. DBS protocols that did not match endogenous synchrony characteristics either had reduced efficacy or actually increased seizure duration. These results suggest that this dynamic may provide an important biomarker for how to improve the efficacy of DBS for treating epilepsy. Furthermore, it suggests that the application of DBS targeted to manipulate subject-specific electrophysiological synchrony levels may provide therapeutic benefit for other neurological or psychiatric pathologies.