Simulation study for the transition from spindles to spike and wave epileptogenesis.

A mathematical model is presented, based on existing anatomical and physiological data, which simulates the behaviour of representative types of cortical cells. It is used to test whether a set of synaptic connections of these cells exists, which, paced by the same rhythmical thalamic input, could produce spindles under normal conditions and spike and wave discharges (SW) under conditions of cortical hyperexcitability. This is possible if the interneurons do not provide recurrent excitatory or inhibitory input on themselves, if the thalamic afferents contact the cortical projecting pyramidal cells through local excitatory neurons, and if the inhibitory interneurons receive input only from the pyramidal cells. The results suggest that an increase of all cortical synaptic actions (both excitatory and inhibitory) is sufficient for the transition from spindles to the first stages in the development of SW discharges in the cortex, whereas the thalamus can be driven to the SW characteristic frequency at the immediate next stages.