[Thalamo non-specific system at different stages of sleep and wakefulness]

Cortical respones to low-frequency (6 to 8 per sec) rhythmic stimulation of the Centrum medianum thalami have been studied in chronic experiments on cats. Three types of recruiting reactions have been readily obtained: 1) with periodic spindling of response amplitudes, the sustained oscillatory type; 2) with spindling only at the beginning of stimulation, the decaying oscillatory type, and 3) with equal amplitudes throughout the stimulation, the aperiodic type. Distinct changes in the type of reactions have been shown--from the aperiodic to the sustained oscillatory type during transition of active awake state to slow-wave sleep, and from the sustained oscillatory type to the aperiodic type during transition of slow-wave sleep to the paradoxical sleep, which is due to changes in the weights of feedbacks in the thalamo-cortical nonspecific system.