Figure 4.

Hypothetical model of the ictal onset zone composed of sparse, non-contiguous, pathological microdomains that are characterized by the ability to generate microseizures, microperiodic epileptiform discharges and high-frequency oscillations. Left: the macroscale ictal onset zone determined by the region generating seizures detected on clinical macroelectrodes (blue). The arrays of microelectrodes are positioned between macroelectrodes and record multi-neuronal unit activity and local field potential oscillations. Centre: three successive times (Time 1, Time 2, and Time 3) and spatial evolution of sub-millimetre (<1 mm³) microdomains that generate microseizures. The clinical ictal onset zone contains microdomain islands (red) generating microseizures that are initially detected on the microelectrodes, but not the clinical macroelectrodes. As the volume of tissue involved in the microseizure discharge increases (Time 3), the seizures are detected on the clinical macroelectrode. Right: enlarged view of the sub-millimetre domains of pathologically interconnected neurons generating microseizures.