Mario Manfredi

Somatic afferent transmission and cortical responsiveness during natural sleep and arousal in the cat

Abstract Both peripherally and centrally evoked somatic responses vary greatly in amplitude according to the level of vigilance. This effect is due both to modifications of afferent transmission along the somatic pathways and to variations in responsiveness of the cortical neurones. In particular: 1. (a) the afferent transmission at the level of the 1st station (gracilis and cuneatus nuclei) does not seem to be affected by the depth of sleep, being unchanged during deep sleep as compared to light sleep; during arousal it may vary greatly according to concomitant behavioural changes; 2. (b) the afferent transmission at the level of the 2nd station (nucleus ventro-postero-lateralis of the thalamus) is constantly affected by the depth of sleep, being maximal during deep sleep; during arousal it can appear either facilitated or depressed according to the depth of the preceding spell of sleep; 3. (c) somatic cortical responsiveness is maximal during light sleep, being apparently depressed during deep sleep and arousal.