Cross-Frequency Interactions in a Recurrent Seizure-Like Events (SLE) Model

Farah, Firas 1 ; Bardakjian, Berj 1, 2

1. Electrical and Computer Engineering, University of Toronto; 2. Institute of Biomaterials & Biomedical Engineering, University of Toronto

A system of coupled Cognitive Rhythm Generators (CRGs), each representing a population of cells, has been used to develop a spontaneous seizure-like events (SLE) model. The CRG is a mathematical construct consisting of three main components: a bank of modes that perform “cognitive” coding transformations on the incoming signal, an oscillator ring device that encodes the output of these modes into instantaneous amplitude and phase values, and finally a static non-linearity mapper that uses these values to create an observable voltage output. The model includes four different cell types, two neuronal and two glial, each of which plays a unique role and exhibits a specific intrinsic frequency range. The neuronal populations include excitatory pyramidal neurons oscillating at an intrinsic frequency in the theta range (~4-6 Hz) and inhibitory interneurons oscillating at an intrinsic frequency in the ripple range (~80-200 Hz). The glial populations include microglia, which play a primarily inhibitory role through synaptic stripping and oscillate at a very low frequency range (~0.2-0.6 Hz), and astrocytes which oscillate at frequencies in the delta range (~1-3 Hz). Each of these groups of CRG units is uniquely essential to the generation of SLEs and the creation of hyperexcitable dynamics. Furthermore, the interactions between the different populations gives rise to cross-frequency coupling, particularly phase-amplitude modulation between low frequency (< 10 Hz) and high frequency rhythms (> 80 Hz).