Selective slow-wave sleep deprivation and time-of-night effects on cognitive performance upon awakening

We evaluated the effects of selective slow-wave sleep (SWS) deprivation and time-of-night factors on cognitive performance upon awakening. Ten normal men slept for 6 consecutive nights in the laboratory: 1 adaptation, 2 basel ine, 2 selective SWS deprivation. and 1 recovery night. Cognitive performan ce was assessed by means of a Descending Subtraction Task after 2, 5. and 7 .5 h of sleep. There was an almost complete selective SWS suppression durin g both deprivation nights, and a significant SWS rebound during the recover y sleep. Regarding cognitive performance, a progressive linear decrease of sleep inertia upon successive awakenings was found during all experimental nights except for the recovery: night. in addition, a significant decrease of sleep inertia was observed upon the morning awakening of the second depr ivation night for the measure of performance speed, and a significant incre ase of sleep inertia upon the morning awakening of the recovery night for t he measure of performance accuracy. The results show that cognitive perform ance upon awakening is adversely affected by sleep depth and that, during t he sleep-wake transition. cognitive performance accuracy is more impaired t han performance speed.