The Detection of Sleep Onset: Behavioral and Physiological Convergence

Abstract

Reaction time (RT), a behavioral measure of arousal, was used to examine standard criteria (Rechtschaffen & Kales, 1968) for assessing sleep onset (SO) and the sensitivity of changes in respiratory patterns at SO. Following 24 hrs without sleep, RT, respiratory, and EEG measures were used to study SO in 12 subjects. Sleep deprivation (SD) permitted multiple examinations of SO in 2 daytime testing periods. Strong relationships between RT and EEG‐based measures of SO serve to confirm the distinction between wakefulness and stage 1 sleep, and moderate to weak correlations between RT and respiratory indices describe the usefulness of the latter. Behavioral, respiratory and EEG assessments of the shift from wakefulness to sleep were observed to be orderly and rapid in these SD volunteers, suggesting that the detection of SO could be sharpened by adding behavioral and respiratory measures to the usual EEG criteria. The close temporal correspondence among these changes has interesting implications for sleep/waking mechanisms.

Vigilance, alertness, or sustained attention: physiological basis and measurement

“…On the OsleR test, sleep onset is considered to occur when a subject fails to press a switch in response to 7 light emitting diode flashes that occur once every 3 s. Since many control subjects have no loss of responsiveness on the time-limited OSleR (Mazza et al, 2005), the lack of behavioral response in a clinical population is considered a marker for sleep onset, rather than simply inattention. Of note, however, there is a significant intersubject difference in terms of relationship of behavioral responsiveness and EEG sleep criteria such that some subjects remain fairly responsive during stage 1 sleep and others do not (Ogilvie et al, 1989).…”

“…During the sleep onset period there is gradually decreased responsiveness to environmental stimuli as assessed by either reaction time or the stimulus intensity needed to elicit a response (Bonnet and Moore, 1982;Ogilvie and Wilkinson, 1984). More recently a standardized measure of behavioral responsiveness to light flashes, the Oxford sleep resistance (OSleR) test, has been used (Bennett et al, 1997) and does correlate strongly with the EEG-based maintenance of wakefulness test (see below) (Krieger et al, 2004).…”

“…Subjects are often still able to respond and may, in fact, not report being asleep when awakened from stage 1 or even stage 2 sleep (Ogilvie and Wilkinson, 1984). In one study, 25% of subjects awakened from clear stage 2 sleep reported they had been awake (Hori, 1994) while another study reported the threshold of subjective sleep (50% reporting being asleep) was 2-4 min after stage 2 onset (Bonnet and Moore, 1982).…”

What subjective experiences determine the perception of falling asleep during sleep onset period?

“…It has been observed that this period is associated with marked changes in a host of physiological and behavioral phenomena, as well as in subjective experience (Ogilvie & Wilkinson, 1984). Physiological phenomena associated with sleep onset include: decrease in high frequency electroencephalographic (EEG) activities (e.g., Azekawa, Sei, & Morita, 1990;Davis, Davis, Loomis, Harvey, & Hobart, 1937, 1938Hori, 1985;Merica, Fortune, & Gaillard, 1991;Rechtschaffen & Kales, 1968;Tsuno et al, 2002); the absence and presence of different event-related potential (ERP) components (for review, see Campbell, Bell, & Bastien, 1992;Harsh, Voss, Hull, Schrepfer, & Badia, 1994); the appearance of slow eye movements (e.g., De Gennaro, Ferrara, Ferlazzo, & Bertini, 2000;Porte, 2004); the absence of elicited skin conductance responses (e.g., Johnson, 1970); a drop in the core body temperature and an increase in the distal skin temperature (e.g., Barrett, Lack, & Morris, 1993;Krauchi, Cajochen, Werth, & Wirz-Justice, 2000;Wehr, 1990); and, substantial, rapid reduction in respiration (e.g., Colrain, Trinder, Fraser, & Wilson, 1987;Naifeh & Kamiya, 1981).…”

“…Physiological phenomena associated with sleep onset include: decrease in high frequency electroencephalographic (EEG) activities (e.g., Azekawa, Sei, & Morita, 1990;Davis, Davis, Loomis, Harvey, & Hobart, 1937, 1938Hori, 1985;Merica, Fortune, & Gaillard, 1991;Rechtschaffen & Kales, 1968;Tsuno et al, 2002); the absence and presence of different event-related potential (ERP) components (for review, see Campbell, Bell, & Bastien, 1992;Harsh, Voss, Hull, Schrepfer, & Badia, 1994); the appearance of slow eye movements (e.g., De Gennaro, Ferrara, Ferlazzo, & Bertini, 2000;Porte, 2004); the absence of elicited skin conductance responses (e.g., Johnson, 1970); a drop in the core body temperature and an increase in the distal skin temperature (e.g., Barrett, Lack, & Morris, 1993;Krauchi, Cajochen, Werth, & Wirz-Justice, 2000;Wehr, 1990); and, substantial, rapid reduction in respiration (e.g., Colrain, Trinder, Fraser, & Wilson, 1987;Naifeh & Kamiya, 1981). Behavioral indicators of sleep onset include: a decrease in sensory threshold, a cessation of responses to external stimuli (e.g., Anliker, 1966;Ogilvie & Simons, 1992;Ogilvie, Simons, Kuderian, MacDonald, & Rustenburg, 1991;Ogilvie & Wilkinson, 1984, 1988Ogilvie, Wilkinson, & Allison, 1989;Simon & Emmons, 1956), and a decrease in muscle strength (e.g., Jacobson, Kales, Lehmann, & Hoedemaker, 1964;Litchman, 1974) were also observed in the course of the sleep onset process. And, as regards the subjective experience of sleep onset, loss of awareness of environmen-tal stimuli and the loss of control over thought processes have both been reported (e.g., Foulkes & Vogel, 1965;Gibson, Perry, Redington, & Kamiya, 1982).…”