Vigilance, sleep and epilepsy.

The correlations between vigilance and epilepsy are manifold. Nearly all epileptic seizures cause a diminution of vigilance extending to unconsciousness. Many of the influences triggering or inhibiting epileptic seizures produce alterations of vigilance or are produced by them. Nearly all chemical influences more or less cause diminution of vigilance. The enhancement of vigilance may inhibit seizures. Decreasing vigilance may act vice versa. As a means to enhance vigilance afferent stimuli are able to trigger seizures. This may be accomplished when singular or rhythmic stimulation of afferents gets the already excited neuronal system oscillating. This principle is also responsible for the strong correlation between triggering of seizures and the sleep/waking cycle with its different grades of neuronal synchronization. On the other hand, inhibition of seizures is possible by a continuously applied stimulation load, which may disturb the increasing excitatory oscillation. Also, conditioning may trigger or inhibit seizures. But the EEG biofeedback only is used to decrease abnormal neuronal activity.