Essai de classification des structures centrales au moyen des variations d'amplitude de leurs réponses évoquées somatiques au cours des cycles veille-sommeil

Abstract

1. 1. The evolution of the amplitude and shape of responses evoked at various cortical and sub-cortical levels during different phases of sleep and wakefulness were studied in thirty-eight cats. In addition to the cerebral recording electrodes. stimulating electrodes were placed on the superficial radial nerve. The means of groups of 25 responses were obtained, using an averaging computer. 2. 2. Three groups of structures could be recognized according to the evolution of their responses during sleep: (a) primary structures (VPL, somato-motor cortex, SII cortex) in which the responses were largest during “fast sleep”; (b) convergent structures (centrum medianum, bulbar reticular formation, caudate nucleus, pallidum, putamen, antero-inferior portion of VL, antero-lateral and suprasylvian gyri) in which the amplitude of responses was large during “slow sleep”, but small during fast sleep or wakefulness; (c) mixed structures (claustrum, red nucleus, postero-superior portion of VL) showed responses with several components which behaved like one or other of the preceding types. In addition new components appeared during fast sleep. 3. 3. The late components of responses from mixed structures were abolished by ablation of the somato-motor cortex but were unaffected by cerebellectomy. 4. 4. The occurrence of late components in the responses of mixed structures during fast sleep was attributed to an increase in the excitatory influence which the somato-motor cortex normally exerts on subcortical structures. Reinforcement of an inhibitory influence of somato-motor cortical origin is also believed to occur during fast sleep and will be the subject of a further paper.