| In an effort to understand basic functional mechanisms that can produce epileptic seizures, we introduce some key features of coupled neural population models that produce "seizure"-like events and dynamics with striking similarities to the ones during the route of the epileptic brain towards seizures. In these models, modified from existing ones in the literature, internal feedback mechanisms are incorporated to maintain normal synchronous behavior despite elevated coupling. While the internal feedback is developed based on basic feedback systems principles, it is also functionally equivalent to actual neurophysiological mechanisms such as homeostasis that act to maintain normal activity in neural systems that are subject to extrinsic and intrinsic perturbations. We hypothesize that a plausible cause of seizures is a pathology in the internal feedback action; normal internal feedback quickly compensates an abnormally high coupling between the neural populations, whereas pathological internal feedback can lead to "seizure"-like high amplitude oscillations. We then develop and test several external seizure-control paradigms that act to achieve the operational objective of maintaining normal synchronous behavior. In particular, we consider open- and closed-loop discrete-time control, closed-loop "switching" and "modulating" control with predefined stimuli, and closed-loop feedback decoupling control. Among these, feedback decoupling control is the consistently successful and robust seizure-control strategy. The proposed model and remedies are consistent with a variety of recent observations in the human and animal epileptic brain, and with theories from nonlinear systems, adaptive systems, optimization, and neurophysiology. The results from the analysis of these models have twofold implications, namely, developing a basic theory for epilepsy and other brain disorders, and the development of a robust seizure-control device through electrical stimulation and/or drug intervention modalities. |
