Spinal motoneuronal excitability during wakefulness and non-REM sleep in hyperkinesis.

Variations in spinal motoneuronal excitability were assessed during wakefulness and non-REM sleep in hyperkinetic and normal children by determining the recovery cycle of the H-reflex following a conditioning stimulus. Reflex facilitation which generally occurs 100-300 msec after a conditioning stimulus was markedly reduced during sleep in both groups and during wakefulness as well in hyperkinetic subjects. Among possible mechanisms which might underlie the observed reductions in facilitation, emphasis is placed on decreased central excitability resulting from depressed fusimotor activity.