Control exerted during sleep by primary cortical areas upon different sensory afferents

Abstract

1. 1. Eighteen cats with chronically implanted electrodes were studied during wakefulness and sleep, with somatic, visual and auditory stimulation; the responses were recorded in different convergent structures: marginalis anterior and suprasylvian gyri, centrum medianum, mesencephalic reticular formation, gigantocellularis nucleus of the bulbar reticular formation. Twenty-five consecutive responses were averaged in each stage of sleep and compared, before and after bilateral removal of the primary sensory areas. 2. 2. In intact animals, and at each level, all the stimuli evoke responses which are largest during drowsiness and slow sleep, smallest during fast sleep and wakefulness. 3. 3. After the removal of both primary cortical areas, the modifications of the corresponding responses during sleep are no longer observed. Each primary cortical area seems to control the associative afferents only within the same sensory system. 4. 4. When the bilateral lesion is incomplete, the normal evolution reappears 3–5 weeks after surgery. 5. 5. The enhancement of the descending control exerted upon the associative afferents by primary afferents during fast sleep, its specificity, its nature and its points of impact are discussed.