Sleep inertia

Incongruities such as the dream character who has the physical attributes of one person that we know and the face of another illustrate an indiscriminate but perhaps functionally significant over-inclusiveness in the categories of unconscious memory systems. We can get at this process by using semantic memory tests of subjects awakened from REM and tested both immediately and later when the sleep inertia is over. Compared to waking and to NREM sleep, we find the expected REM enhancement of weak primes (i.e., loose associations) but, to our surprise, not of strong primes (strong associations). 

It is recognized that various MWT trial durations and rules for termination of trials have been used depending on the setting. Choices among these variations allow the MWT to be adapted to a variety of settings and needs. For example, if there are concerns about sleep accumulation during trials or about sleep inertia after... 

Van Dongen HPA, Price NJ, Mullington JM, Szuba MP, Kapoor SC, Dinges DF. Caffeine eliminates psychomotor vigilance deficits from sleep inertia. Sleep 2001 24 813-819. 

Existing mathematical models predicting cognitive readiness/performance from sleep/wake history are based on the interaction of three factors. These factors are sleep homeostasis, circadian rhythm, and sleep inertia (12). Three-factor models successfully predict performance effects of acute, total sleep deprivation and... 

Acherman P, Werth E, Dijk D, Borbely AA. Time course of sleep inertia after nighttime and daytime sleep episodes. Arch Ital Biol 1995 134 109-119. 

Brack D, Pisani DL. The effects of sleep inertia on decision-making performance. J Sleep Res 1999 8 95-103. 

Muzet A, Nicolas A, Tassi P, DeWasmes G, Bonneau A. Implementation of napping in industry and the problem of sleep inertia. J Sleep Res 1995 4(suppl 2) 67-69. 

Ferrara M, DeGennaro F, Bertini M. Time-course of sleep inertia upon awakening from sleep with different sleep homeostasis conditions. Aviat Space Environ Med 2000 71(3) 225-229. 

The extent to which naps will be beneficial, in terms of improved self-perceived alertness, performance, and objective alertness, is likely to depend on a number of factors. The factors of particular significance that will be addressed in this chapter include (a) sleep inertia, (b) nap duration, (c) nap sleep infrastructure, (d) circadian timing, (e) prior wake time, (f) napping strategies for periods of extended wakefulness, (g) individual differences, and (h) the setting (laboratory vs. applied settings). The discussion will now turn to the first of these factors, sleep inertia. 

Sleep inertia, the experience of inferior task performance and/or disorientation occurring immediately after awakening from sleep (10, p. 226), is a well-documented consequence of napping (11). Although sleep inertia is said to dissipate... 

To summarize, sleep inertia is a factor to consider when implementing a napping strategy. As sleep inertia appears to be affected by the duration of slow-wave sleep within the sleep period and slow-wave sleep occurring at arousal, sleep inertia tends to accompany naps in excess of 20-30 min. For this reason, as well as the fact that naps greater than 20 min appear to produce characteristically different postnap effects compared to naps of shorter duration, naps in excess of 20 min duration will henceforth be referred to as long naps and those 20 min and shorter will be termed brief naps. 

Notwithstanding the initial effects of sleep inertia that may accompany long naps, they have been shown to produce beneficial effects after normal nocturnal sleep (26-29), sleep restriction (30), total sleep deprivation (31), as well as during experimental night shifts (32,33) and periods of sustained wakefulness (1). Reported benefits include increased post-nap sleep latency (30,31,33), improved... 

On balance, while long naps appear to be more beneficial following total sleep deprivation, any benefit must be weighed against their limitations of sleep inertia and possible disruptions to the subsequent nocturnal sleep period. After normal nocturnal sleep or mildly restricted nocturnal sleep, brief naps would be... 

To summarize the findings presented thus far, one would conclude that naps are differentially beneficial over time according to the duration of the nap. The available evidence suggests that brief naps (of approximately 10 min) produce immediate improvements in alertness and performance lasting for at least 3 hr. On the other hand, longer naps typically produce an initial period of sleep inertia upon awakening, the duration of which may vary according to the amount of... 

Long naps may produce an immediate period of impaired alertness and performance (i.e., sleep inertia). 

JewettME, Wyatt JK, Ritz-De Cecco A, Khalsa SB, Dijk D-J, Czeisler CA. Time course of sleep inertia dissipation in human performance and alertness. J Sleep Res 1999 8 1-8. 

Naitoh P, Kelly T, Babkoff H. Sleep inertia best time not to wake up Chronobiol Int 1993 10 109-118. 

Guido P, Rosenthal L, Nykamp K, et al. Sleep inertia following one and twenty minute nap opportunities. Sleep 1998 21 165. 

Ferrara M, De Gennaro L. The sleep inertia phenomenon during the sleep-wake transition theoretical and operational issues. Aviat Space Environ Med 2000 71 843-848. 

The sleep-dependent component shows highest alertness immediately after sleep resembling the recovery efieci, and then alertness decreases with time. Therefore, this component is sometimes called time-since-sleep effect. Sleep inertia and the time-since-sleep component are influenced by quantity and quality of previous sleep. However, the quantitative elfect of sleep quality and quantity on these components is less well documented. 

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