Physiological basis: how NREM sleep components can promote and REM sleep components can suppress seizure discharge propagation.

OBJECTIVES

To describe how the neural generators of different sleep components can provoke seizure discharge propagation during NREM sleep and can suppress it during REM sleep.

METHODS

Experimental manipulations of discrete physiological components were conducted in feline epilepsy models (n=64), mostly in the systemic penicillin epilepsy model of primary generalized epilepsy and the amygdala kindling model of the localization-related seizure disorder, temporal lobe epilepsy. Procedures included seizure induction as well as quantifying norepinephrine concentrations (microdialysis) and the sleep-waking state distribution of seizures before and after lesions, systemic and localized drug administration and/or photic stimulation.

RESULTS

(1) Neural generators of synchronous EEG oscillations, including tonic background slow waves and phasic 'arousal' events (sleep EEG transients such as sleep spindles, k-complexes), can combine to promote electrographic seizure propagation during NREM and drowsiness; anti-gravity muscle tone permits seizure-related movement. (2) Neural generators of asynchronous neuronal discharge patterns can reduce electrographic seizures during alert waking and REM sleep; skeletal motor paralysis blocks seizure-related movement during REM. (3) Etiology of the seizure disorder can interact with sleep and arousal mechanisms to determine sleep-waking state distribution of interictal and ictal events.

CONCLUSIONS

Differential effects of NREM versus REM sleep components on seizure discharge propagation are to some extent non-specific and in other ways specific to seizure etiology.