The Beneficial Effect of Sleep in an Extended Jenkins and Dallenbach Paradigm

Retention of a paired-associate list of common nouns was tested under two conditions: original learning at night prior to 8 hrs of sleep (Sleep condition), and original learning in the morning prior to a day of normal waking activity (Waking condition). Both conditions were subdivided so that retention was tested at intervals of 8, 16, and 24 hrs after original learning. For both paced and free recall measures of retention, the Sleep condition proved superior to the Waking condition at the 8 hr interval. At 24 hrs, when the amounts of sleep and waking were equated across both conditions thus normalizing for potential interference, the superiority of the Sleep condition over the Waking condition was also observed. There were no differences in retention between the Sleep and Waking conditions at 16 hrs after original learning. This finding was largely influenced by improved recall on the part of subjects in the Waking condition in the interval between 8 and 16 hrs. It was concluded that the consolidation during sleep of verbal materials learned shortly before sleep onset has a beneficial effect on their recall and temporal stability in the 8 to 24 hr period following original learning.     

The Detection of Sleep Onset: Behavioral and Physiological Convergence

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.     

Sleep patterns in the parakeet Melopsittacus undulatus

Electrophysiological and behavioral studies of vigilance states were performed on adult specimens of the parakeet Melopsittacus undulatus. Four states of vigilance were identified: Wakefulness, drownsiness, slow wave sleep and paradoxical sleep. During wakefulness, a low voltage fast EEG pattern was observed. This pattern was progressively increasing in amplitude and decreasing in frequency when passing from drowsiness to slow wave sleep. Sleep spindles were not present. Slow wave sleep was frequently interrupted by paradoxical sleep episodes of short duration (6.4 +/- 3.2 sec), characterized by an EEG pattern similar to that of waking state. During wakefulness there were body and eye movements. This motor activity decreased when animals went into drowsiness and slow wave sleep. Paradoxical sleep was characterized by slight motor automatisms, including sometimes ocular movements.     

Timing of spontaneous sleep-paralysis episodes

The objective of this prospective naturalistic field study was to determine the distribution of naturally occurring sleep-paralysis (SP) episodes over the course of nocturnal sleep and their relation to bedtimes. Regular SP experiencers (N = 348) who had previously filled out a screening assessment for SP as well as a general sleep survey were recruited. Participants reported, online over the World Wide Web, using a standard reporting form, bedtimes and subsequent latencies of spontaneous episodes of SP occurring in their homes shortly after their occurrence. The distribution of SP episodes over nights was skewed to the first 2 h following bedtime. Just over one quarter of SP episodes occurred within 1 h of bedtime, although episodes were reported throughout the night with a minor mode around the time of normal waking. SP latencies following bedtimes were moderately consistent across episodes and independent of bedtimes. Additionally, profiles of SP latencies validated self-reported hypnagogic, hypnomesic, and hypnopompic SP categories, as occurring near the beginning, middle, and end of the night/sleep period respectively. Results are consistent with the hypothesis that SP timing is controlled by mechanisms initiated at or following sleep onset. These results also suggest that SP, rather than uniquely reflecting anomalous sleep-onset rapid eye movement (REM) periods, may result from failure to maintain sleep during REM periods at any point during the sleep period. On this view, SP may sometimes reflect the maintenance of REM consciousness when waking and SP hallucinations the continuation of dream experiences into waking life.     

The characteristics of recovery sleep when recovery opportunity is restricted

STUDY OBJECTIVES: The aim of this study was to investigate the recovery of sleep and waking functions following one night of total sleep deprivation, when recovery opportunity was either augmented or restricted. DESIGN: The 9-day laboratory study involved a baseline night, a night of sleep loss (approximately 40 h) followed by 5 nighttime recovery sleep periods. Recovery consisted of either five 9-h sleep opportunities or five 6-h sleep opportunities. SETTING: All data collection took place in a controlled laboratory environment at the Centre for Sleep Research. PARTICIPANTS: A total of n = 20 healthy adults (18-35 yrs) participated in the study. RESULTS: Each sleep period was recorded using a standard polysomnographic EEG montage. Waking functions were assessed every 2 hours during all wake periods, using a 10 minute psychomotor vigilance task (PVT) and a subjective alertness visual analogue scale (VAS). Sleep analyses indicated that across the week TST, SOL, REM, and sleep efficiency varied significantly between the 2 conditions, but amounts of SWS did not. Waking functions in the 9-h condition recovered after one sleep period. In the 6-h condition however, mean response time on the PVT was 10% below baseline and subjective alertness 20% below baseline for the entire recovery period. CONCLUSIONS: The results suggest that TST is a key factor in determining recovery. When recovery opportunity is restricted, both sleep variables and measures of waking functions do not recover.     

Relationship of Rapid Eye Movement Density to the Prior Accumulation of Sleep and Wakefulness

Ocular activity during the REM stage of sleep was studied for the purpose of determining what effect previous sleep and waking would have on the intensity of that activity. Eleven Ss slept to satiation during a 54-hr session and then, after a day of waking, slept for another night. REM density (i.e., number of eye mvts per min of REM period) rose progressively during the first night and morning, and then remained at a high level for the remainder of the 54 hrs; the mean REM density for Night 2 and also for Night 3 was about double the REM density of Night 1. Multiple regression analysis indicated that the amount of prior sleep was positively correlated with REM density whereas the amount of waking was negatively correlated. Peak REM density occurred after a mean of 9.88 hrs of sleep. Thereafter, periods of waking alternated with periods of sleep while the REM density oscillated at its peak level. It was concluded that REM density reflects the output of a sleep-waking negative feedback circuit.     

Sleep homeostasis in Drosophila melanogaster

STUDY OBJECTIVES: The fruit fly Drosophila melanogaster is emerging as a promising model system for the genetic dissection of sleep. As in mammals, sleep in the fruit fly is a reversible state of reduced responsiveness to the external world and has been defined using an array of behavioral, pharmacologic, molecular, and electrophysiologic criteria. A central feature of mammalian sleep is its homeostatic regulation by the amount of previous wakefulness. Dissecting the mechanisms of homeostatic regulation is likely to provide key insights into the functions of sleep. Thus, it is important to establish to what extent sleep homeostasis is similar between mammals and flies. This study was designed to determine whether in flies, as in mammals, (1) sleep rebound is dependent on prior time awake; (2) sleep deprivation affects the intensity, in addition to the duration, of sleep rebound; (3) sleep loss impairs vigilance and performance; (4) the sleep homeostatic response is conserved among different wild-type lines, and between female and male flies of the same line. DESIGN: Motor activity of individual flies was recorded at 1-minute intervals using the infrared Drosophila Activity Monitoring System during 2 baseline days; during 6, 12, and 24 hours of sleep deprivation; and during 2 days of recovery. Sleep was defined as any period of uninterrupted behavioral immobility lasting > 5 minutes. Sleep continuity was measured by calculating the number of brief awakenings, the number and duration of sleep episodes, and a sleep continuity score. Vigilance before and after sleep deprivation was assessed by measuring the escape response triggered by 2 different aversive stimuli. SETTING: Fly sleep research laboratory at UW-Madison. PARTICIPANTS AND INTERVENTIONS: Adult flies of the Canton-S (CS) strain and 116 other wild-type lines (> or = 16 female and > or = 16 male flies per line). MEASUREMENTS AND RESULTS: In wild-type CS flies, as in mammals, the amount of sleep recovered after sleep deprivation was dependent on prior time awake. Relative to baseline sleep, recovery sleep in CS flies was less fragmented, with longer sleep episodes, and was associated with a higher arousal threshold. Sleep deprivation in CS flies also reduced performance. Sleep duration and continuity increased after 24 hour of sleep deprivation in all the other wild-type lines tested. CONCLUSION: The sleep homeostatic response in fruit flies is a stable phenotype and shares most of, if not all, the major features of mammalian sleep homeostasis, thus supporting the use of Drosophila as a model system for the genetic dissection of sleep mechanisms and functions.     

Electrographic correlates of sleep behavior in a primitive mammal, the armadillo Dasypus novemcinctus

Sleep behavior in 5 armadillos was studied over a continuous 24-hr period in order to evaluate certain hypotheses concerning the relation of life style and phylogenetic rank to sleep. The physical security of a sleeping armadillo, according to a life style hypothesis, should allow it to sleep extensively and to have a high proportion of paradoxical sleep (PS). In this study armadillos slept an average of over 77% of the day. Armadillos apparently are phylogenetically advanced enough to display PS and, depending on criteria and data interpretation, were observed to spend approximately 8.9%–21.5% of their sleep time in PS. During the short and scattered wakefulness periods armadillos were vigorously active, with no periods of awake quiescence lasting more than 2 min. Sleep onset was unusually sudden, occurring in 11–19 episodes per day. Rectal temperatures varied erratically over a wide range and did not correlate with behavioral state. The typical slow wave EEG pattern occurred about 50% of the total sleep time, with durations of a given period ranging from 0.75–375 min. Activated EEGs during sleep were associated with 4 different categories of rapid eye movement and neck muscle activity. Activated EEG episodes ranged from 0.8–1.6 min and were interspersed with abrupt transitions among the slow wave periods. Analysis of PS was confounded by the short periods of activated EEGs and by the absence of nuchal atonia. At least some of the categories of activated EEG could have reflected shivering or transient arousal from slow wave sleep, rather than PS.     

Behavioural sleep in the giraffe (Giraffa camelopardalis) in a zoological garden

Behavioural sleep was assessed for 152 nights in 5 adult, 2 immature and 1 juvenile giraffes at a zoological garden, using continuous time-lapse video recording. Sleep occurred while the giraffes were standing (SS) and in recumbency (RS). Paradoxical sleep (PS) was recognized by the peculiar positioning of the head on the croup and by phasic events. The 24-h sleep profile had a main bimodal nocturnal sleep period between 20.00 and 07.00 hours, with a trough between 02.00 and 04.00 hours, and several short naps between 12.00 and 16.00 hours. Total sleep time (TST), excluding the juvenile, was 4.6 h, whereby PS comprised only 4.7%. TST was not age dependent, but the lowest amount of RS and the highest amount of SS occurred in the oldest and the two oldest animals, respectively. Sleep was fragmented, as indicated by the predominance of RS episodes lasting less than 11 min. Sleep cycle duration was very variable with most values between 1 and 35 min (when no waking or RS was allowed within PS episodes), or 6–35 min (when the criteria for ending a PS episode allowed 1–2 min interruptions by RS). There were several indications for sleep regulation: (i) RS and SS complemented each other to yield a relatively stable daily value of TST; (ii) sleep was redistributed on nights following a day when the giraffes spent a few hours in an outside enclosure. The first peak of the bimodal sleep profile was absent and RS was more prominent in the second half of the night compared with nights following days spent in the barn; and (iii) napping was followed by a minor reduction of RS and an increase in SS in the subsequent night compared with nights following days without naps.     

Sleep cyclicity in infants during the earliest postnatal weeks

Cyclicity within sleep was investigated in 20 fullterm infants who were monitored in the home for 24-hour periods when they were 2-5 weeks old. Using a pressure sensitive mattress in the crib, analog signals from the baby's respiration and body movements were computer scored for: Quiet Sleep, Active Sleep, Active-Quiet Transitional Sleep, Sleep-Wake Transition, and Wakefulness. Sleep episodes with at least four recurrences of Quiet Sleep were analyzed for cyclicity. Significant cyclicity of Quiet Sleep was found in 49 of the 55 sleep episodes analyzed. The mean Quiet Sleep recurrence period was 63.2 minutes. Eighteen of the 20 infants exhibited cyclicity on one or more weeks. Thus, sleep during the neonatal period is generally characterized by the presence of cyclicity. Cyclicity was not related to other parameters of the sleep cycle, but was correlated with stability of state patterning over weeks. The results provide new evidence for neurobehavioral competence of the neonate in terms of sleep organization.     

Recovery of Performance During Sleep Following Sleep Deprivation

Very few studies have systematically examined recovery of performance after sleep deprivation. In the present study, 12 young adult males were sleep deprived for periods of 40 and 64 hrs. Each period was preceded by baseline nights of sleep and followed by two recovery nights of sleep. Immediate recall and reaction time were tested at 2300, 0145, 0400, 0615, and 0830 during baseline, deprivation, and recovery nights. Performance efficiency showed a progressive decline after 2 hrs of recovery sleep following both periods of deprivation. Return to baseline was apparent after 4 hrs of steep following 40 hrs awake and after 8 hrs of sleep following 64 hrs awake. These results suggested that, in terms of behavioral efficiency, an equal amount of sleep is not required to compensate for sleep lost.     

The effects of repeated audiogenic convulsions on the organization of sleep in rats

The organization of sleep in Krushinskii—Molodkina rats, with an inherited predisposition to audiogenic convulsions, was studied during and after repeated audiogenic convulsions consisting of two, three, or five relatively rare (separated by intervals of 90 min) or three, five, or nine relatively frequent (separated by intervals of 45 min) generalized clonic-tonic convulsions. In rats subjected to repeated seizures with rare convulsions, behavior in the periods between individual convulsions was dominated by passive waking (75.2 ± 4.6% of the time), with a low level (24.8 ± 4.3%) of slow-wave and a complete absence of fast-wave sleep, i.e., there was selective removal of the fast-wave sleep phase from the sleep-waking cycle of the rats. In rats subjected to frequent seizures with frequent convulsions, the period between convulsions showed only passive waking, with complete loss of slow-wave and fast-wave sleep, i.e., total sleep deprivation took place. The minimal latent period before the appearance of the first episodes of slow-wave sleep after repeated convulsions was 59.9 ± 10.8 min; that for fast-wave sleep was 158.2 ± 13.4 min. However, the first episodes of slow-wave and fast-wave sleep had an essentially normal structure, though episodes shorter than those in controls were seen, albeit more rarely. Despite the prolonged (up to 7 h) absence of slow-wave sleep during seizures and the prolonged (8.5 h) decrease in fast-wave sleep, there was no compensatory increase in the levels of these states in the sleep-waking cycle during the 12 h of recovery after seizures. Overall, the recovery period after repeated seizures was characterized by an increase (compared with controls) in the total proportion of waking in the behavior of the rats, with a decrease in the total duration of slow-wave and fast-wave sleep. It is concluded that the paroxysmal status significantly disorganizes the operation of the sleep-generating structures of the brain. The functioning of the systems responsible for slow-wave sleep is less affected, while impairments of the activity of the systems responsible for the formation of fast-wave sleep are more significant, affecting primarily the mechanisms triggering this sleep phase. __________ Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 91, No. 7, pp. 740–751, July, 2005.     

Temporal pattern of hippocampal high-frequency oscillations during sleep after stimulant-evoked waking

Hippocampal ripple oscillations (140-200 Hz) are believed to be critically involved in the consolidation of memory traces during slow-wave sleep (SWS). We investigated the temporal pattern of ripple occurrence in relation to sleep phases following different types of waking. Amphetamine, the atypical wakening drug modafinil or non-pharmacological sleep deprivation lead to an increased ripple occurrence ("rebound") during the subsequent SWS episode. Waking of the same duration evoked by amphetamine or sleep deprivation led to a ripple rebound of similar extent (approximately 200%). The mean intraripple frequency was also elevated by up to 20 Hz during SWS following all treatments. Ripple amplitude was significantly increased only in experiments with amphetamine. Ripple occurrence but not intraripple frequency clearly correlated with the antecedent waking duration independent of treatment. Recovery of ripple occurrence and frequency to the pretreatment level during SWS depended on SWS duration. At the end of the recovery period paradoxical sleep (PS) acted like waking, elevating ripple occurrence during subsequent SWS episodes. On the other hand, PS decreased ripple occurrence if recovery from the rebound was not yet complete. Thus occurrence and structure of ripple oscillations are regulated by the timing and duration of previous SWS, PS and waking episodes.     

Acute deprivation of the terminal 3.5 hours of sleep does not increase delta (0-3-Hz) electroencephalograms in recovery sleep

Sleep electroencephalograms (EEG) and electrooculograms were recorded in nine young adult males on a baseline night, a night in which they were deprived of an average of 3 hr 27 min of sleep by early awakening, and on a recovery night. Records were analyzed by visual sleep stage scoring and period-amplitude analysis; the results of both were tabulated by successive nonrapid eye movement periods (NREMPs) and rapid eye movement (REM) periods. Neither visually scored delta nor REM measures were affected by this substitution of waking for sleep. Although there was a significant increase in the 0-3-Hz time/epoch on the recovery night, this finding was not confirmed in the accompanying report. These results, taken in association with data from previous studies, are consistent with the hypothesis that, in an acute experiment, visually scored delta and computer-measured 0-3-Hz EEGs increase above the baseline levels only if there has been loss of stage 3/4 EEG (or of sleep) from the first two NREMPs. The findings here are inconsistent with older reports and indicate that further parametric data are required to construct a quantitative model of the relation of sleep EEG waveforms to the duration of prior waking.     

Sleep characteristics in the turkey Meleagris gallopavo

Electrophysiological and behavioral characteristics of the states of vigilance were analyzed in chronically implanted specimens of the turkey Meleagris gallopavo (M. gallopavo). Five different states of vigilance were observed throughout the nyctohemeral period: active wakefulness (AW), quiet wakefulness (QW), drowsiness (D), slow wave sleep (SWS) and rapid eye movement (REM) sleep.These states exhibit characteristics similar to those described in other bird species. Sleep periods displayed a polyphasic distribution; however, they showed the tendency to concentrate between 2100 and 0900 h in spite of the fact that the recordings were carried out under constant illumination. Sleep period occupied 45.71% of the nyctohemeral cycle, 43.33% corresponded to SWS, while 2.38% to REM sleep. The average duration of the REM sleep phase was very short, lasting 7.7+/-0.55 s (mean+/-S.D.). In contrast, its frequency was very high with an average recurrence of 268+/-63 phases throughout the nyctohemeral cycle. The short duration of REM sleep phase presented by the turkey as by other bird species studied up to now may be dependent upon genetic factors shared by this group of vertebrates.     

Baseline sleep-wake patterns in the pointer dog.

The 24-hr electrographic patterns (EEG, EOG, EMG) of six normal pointer dogs were recorded in a laboratory setting. Two states of sleep (slow-wave and rapid eye movement) and wakefulness (alert and drowsy) were identified. The total recording period comprised 44% of alert wakefulness, 21% of the drowsy state, while slow-wave sleep occupied 23% and REM sleep 12% of the time. The mean length of a REM sleep episode averaged 6 min and the mean REM sleep cycle was 20 min. The mean polycyclic sleep-wake cycle was 83 min. Sleep episodes averaged 45 min and the mean waking episode was 38 min. There was an average of two REM sleep episodes per sleep-wake cycle. The dog has a propensity to sleep over a 16-hr interval from 1300 to 0500 but the most sleep occurred between 2100 and 0400 hr during darkness.     

American time use survey: sleep time and its relationship to waking activities

STUDY OBJECTIVES: To gain some insight into how various behavioral (lifestyle) factors influence sleep duration, by investigation of the relationship of sleep time to waking activities using the American Time Use Survey (ATUS). DESIGN: Cross-sectional data from ATUS, an annual telephone survey of a population sample of US citizens who are interviewed regarding how they spent their time during a 24-hour period between 04:00 on the previous day and 04:00 on the interview day. PARTICIPANTS: Data were pooled from the 2003, 2004, and 2005 ATUS databases involving N=47,731 respondents older than 14 years of age. INTERVENTIONS: N/A. RESULTS: Adjusted multiple linear regression models showed that the largest reciprocal relationship to sleep was found for work time, followed by travel time, which included commute time. Only shorter than average sleepers (<7.5 h) spent more time socializing, relaxing, and engaging in leisure activities, while both short (<5.5 h) and long sleepers (> or =8.5 h) watched more TV than the average sleeper. The extent to which sleep time was exchanged for waking activities was also shown to depend on age and gender. Sleep time was minimal while work time was maximal in the age group 45-54 yr, and sleep time increased both with lower and higher age. CONCLUSIONS: Work time, travel time, and time for socializing, relaxing, and leisure are the primary activities reciprocally related to sleep time among Americans. These activities may be confounding the frequently observed association between short and long sleep on one hand and morbidity and mortality on the other hand and should be controlled for in future studies.     

Age differences in the spontaneous termination of sleep

The stage from which the spontaneous ending of sleep occurred was investigated in 138 sleep episodes obtained from 14 younger (19-28 years) and 11 older (60-82 years) individuals. The possible influences of circadian phase and quality of the preceding sleep period, as well as the impact of aging on characteristics of sleep termination were examined. Under experimental conditions in which subjects were isolated from time cues, and behavioral options to sleep were limited, no age-associated differences in the duration of sleep periods, or in the number or duration of REM episodes were observed. Despite similar percentages of NREM (stages 2-4) and REM sleep across age groups, younger subjects awakened preferentially from REM while older subjects did not. Of the sleep episodes obtained from older subjects, those with sleep efficiencies higher than the median were more likely to terminate from REM than those with lower sleep efficiencies. For all subjects, the REM episodes from which sleep termination occurred were truncated relative to those that did not end the sleep period. In addition, nonterminating REM episodes that were interrupted by a stage shift were most often interrupted by brief arousals to stage 0. Such arousals within nonterminating REM episodes occurred, on average, after a similar duration as the terminating point of sleep-ending REM episodes. The results from this study demonstrate that there are age-related differences in the sleep stage from which spontaneous awakenings occur, and that these differences may be due in part to the quality of the sleep period preceding termination. Findings regarding the characteristics of both terminating and nonterminating REM episodes are consistent with the notion that the neural and biochemical context of REM sleep may facilitate a smooth transition to wakefulness. It is speculated that age-associated changes in sleep continuity may render unnecessary the putative role of REM sleep in providing a 'gate' to wakefulness.     

Effects of Sleep Deprivation on Measures of the Febrile Reaction and the Recovery of Somatovisceral Functions and Sleep in Endotoxemia

Electroencephalographic methods were used to study the effects of total sleep deprivation on thermoregulatory measures of the fever response in pigeons (Columba livia): brain temperature, peripheral vasomotor reactions, thoracic muscle contractile activity, and the recovery of somatic functions and the time characteristics of waking and sleep in lipopolysaccharide (LPS)-induced endotoxemia. Sleep deprivation during the period in which the quantity of slow-wave sleep increased on administration of LPS induced decreases in the latent period of fever onset and in the duration of fever, along with more significant increases in brain temperature and the level of muscle contractile activity as compared with the effects of LPS alone. The period after sleep deprivation was characterized by more prolonged recovery of muscle contractile activity and the time characteristics of sleep and waking states, along with more prolonged compensatory “rebound” of slow-wave sleep as compared with the effects of sleep deprivation alone. Thus, sleep deprivation in endotoxemia led to decreases in the latent period of fever onset, exacerbation of fever, and increases in the latent period of recovery of physiological functions.     

Sleep deprivation increases susceptibility to kindled and penicillin seizure events during all waking and sleep states in cats

The timing of amygdala kindled and penicillin seizures was studied throughout the sleep-wake cycle in eight cats following near total sleep deprivation and a control procedure that did not affect sleep time. Sleep loss was induced by 24-h exposure to a modified "flower pot" procedure employing a small pedestal. The control procedure consisted of 24-h exposure to a larger pedestal. Sleep loss increased susceptibility to generalized kindled and penicillin seizures during all waking and sleep states but did not alter temporal patterns of seizure susceptibility. Both before and after sleep loss, kindled cats showed maximal seizure susceptibility, indexed by lowest seizure thresholds, during slow wave sleep (SWS) and transitions from SWS to REM sleep (REMS). The spike-wave discharges and motor seizures of systemic penicillin epilepsy were always most frequent during SWS and during drowsiness after awakening. Both models were invariably most resistant to seizures during stable REMS. To explain sleep- and sleep loss-activated seizures, we summarized previous work suggesting that sleep abnormalities dictate the timing of seizures and are exacerbated by sleep loss. Abnormal behavioral arousals and pathological somatomotor system excitability occur in both models and are particularly pronounced during seizure-prone intervals. Sleep loss may magnify somatomotor system hyperexcitability patterns in all states, thus allowing abnormal motor arousals and seizures to intrude during seizure-prone and seizure-resistant sleep and waking states.