Motor phenomenology of cobalt experimental epileptic focus in the motor cortex of the cat during various stages of vigilance

Abstract

1. 1. On eighteen chronic cats, epileptic focus of the left motor cortex was produced by topical application of cobalt powder. The motor phenomena in the contralateral limb accompanying the epileptic discharges were studied during sleep and wakefulness. 2. 2. Electrodes were implanted for recording EEG and EMG of the neck muscles, electrooculograms and movements of the contralateral limb. 3. 3. Results showed that during wakefulness, single myoclonic jerks or clonic seizures of the right limb were constantly associated with sporadic or repetitive discharges of the motor cortex. During slow wave sleep, epileptic discharges were still present but clonic movements diminished and often disappeared with deepening of sleep. During fast wave sleep, epileptic discharges over the cortex were usually similar to those seen in waking, but all epileptic movements secondary either to sporadic discharge or electrical seizure we re blocked. Paradoxically, physiological muscular twitches characteristic of fast wave sleep were always present in the same epileptic cats. 4. 4. The pyramidal discharge, recorded by a bipolar electrode at the level of the left pyramidal tract,was studied during seizures both in waking and sleeping states. It remained unchanged during seizures and persisted as long as the cortical discharges whatever the state of vigilance of the animal. 5. 5. Mechanisms responsible for the disappearance of epileptic movements during fast wave sleep, in spite of the presence of physiological muscular twitches were, discussed, as well as correlations between these results and human epilepsy.