[Activity of the cortical neurons during paroxysmal after-discharge]

Features of electrographic and neuronal activities of occipital region of the cortex following repetitive electrical stimulation with the threshold intensity for triggering the electrographic paroxysmal after--discharges in the region of stimulation and for triggering the spreading motor paroxysmal after--discharge in the cortex, were studied in chronic experiments on unanesthetized rabbits. The frequency of paroxysmal potentials was 8 1/s in the focus of the local paroxysmal after--discharge and 15 1/s in the focus of spreading after-discharge. In the focus of spreading paroxysmal after--discharge the "epileptic" neurons in deep layers of cortex were observed; neurons in deep layers of the local paroxysmal after--discharge discharged mainly with single impulses or with trains of 2--3 impulses in the rhythm of paroxysmal potentials. The primary paroxysmal activity focus in upper cell layers is supposed to exist during local after--discharge. The changes in activity of deep cell layer neurons are discussed as the necessary condition for the spreading of paroxysmal after--discharge.