Sleep Medicine Reviews, Vol. 00, No. 0, pp 1±19, 2002 doi:10.1053/smrv.2001.0202, available online at http://www.idealibrary.com on

Awakening from T. AÊ kerstedt1, M. Billiard2, M. Bonnet3, G. Ficca4, L. Garma5, M. Mariotti6, P. Salzarulo7 and H. Schulz8

1 Karolinska Institute, Stockholm, Sweden, 2 Gui de Chauliac Hospital, Montpellier, France,3 Dayton Department of Veterans Affairs, Medical Center, USA, 4 University of Naples, Italy, 5 Hopital^ de la SalpeÃtrieÁre Paris France, 6 University of Milano, Italy, 7 University of Florence, Italy, 8 Helios Klinikum, Erfurt, Germany

KEYWORDS Summary Awakening is a crucial event for the organism. The transition from sleep awakening, thalamus, to waking implies physiological processes which lead to a new behavioural state. sleep architecture, Spontaneous awakenings have varying features which may change as a function of time of day, several factors. The latter include intrasleep architecture, circadian phase, time awake, biological rhythms, age, or disordered sleep. Despite its clear theoretical and clinical importance, the aging, development, topic of awakening (in humans) has received little so far. This contribution focuses on major issues which relate to awakening from both basic (experimental) , , and clinical research. Recentknowledge on neurophysiological mechanisms is reported. The experimental data which provide in the human suggestions on the regulation of awakening are discussed, mainly those concerning sleep architecture and homeostatic/circadian factors also in a life-span perspective, since age is a powerful factor which may in¯uence awakening. Clinical contributions will examine two main sleep disorders: insomnia and hypersomnia. Daytime functioning is shown in insomniac patients and compared to other pathologies like . A ®nal section evokes links between some types of night waking and psychological factors. & 2002, Elsevier Science Ltd. All rights reserved.

INTRODUCTION of minutes, and (iii) longlasting and consistent awake- nings, often representing the termination of a full sleep Awakening is a crucial eventfor theorganism, sepa- episode. rating sleep and wakefulness. The transition from sleep In fact both terms, awakening and arousal, are used to waking implies physiological processes which lead to in the literature often with similar, even identical a new behavioural state. Transitions between sleep and meaning. An epistemological discussion about the wakefulness in humans encompass a wide spectrum of right to use one of these terms is beyond the scope state changes, different in duration and characteristics: of this review. However it could be remarked that (i) ultrashort arousals in the range of seconds, (ii) short ``arousal'' is mainly used in neurophysiology to indicate spontaneous awakenings from sleep in the range cortical events and in clinical domain for physiological events linked to respiratory pathology; awakening includes a behavioural component. Correspondence should be addressed to: Prof. Piero Salzarulo, Dept. of Psychology, University of Florence, Via S. NiccoloÁ 93, Non-provoked awakenings, either ®nal or intra- 50125 Florence, Italy. E-mail: [email protected]®.it night, have varying features: their number, temporal

1087±0792/02/000000 ‡ 00 $35.00/0 & 2002, Elsevier Science Ltd. All rights reserved. 2 T. AÊ KERSTEDT ET AL. placement, cognitive characteristics and the duration (i.e. Centralis Lateralis), an increase of unitary activity, of the following wakefulness may change as a func- and a remarkable change of the discharge pattern, tion of several factors. The latter include intrasleep anticipate the EEG changes by tenths of seconds during architecture, circadian phase, time awake, age, or transitions from slow-waves-sleep (SWS) to wakeful- disordered sleep. Despite its clear theoretical and ness (W) [2]. Transition to wakefulness is also marked, clinical importance, the topic of awakening (in humans) in many brain regions, by a widespread activation of has received little attention so far. c-fos and others immediate-early genes, which could The present cooperative effort is an attempt to raise be the molecular correlates of electrophysiological the interest in this area of sleep research. It was activation [3]. inspired by a symposium at the 14th Congress In the Ventralis Postero Lateralis (VPL), a speci®c (Madrid) of the European Sleep Research Society. sensory nucleus of the thalamus, the response to We decided to focus this contribution on major issues peripheral physiological stimulation during sleep shows which relate to awakening from both basic (experi- three main components: a very brief and scanty mental) and clinical research. excitatory response, followed by a long period of Firstly, an insight in the up-to-date neurophysio- discharge suppression and by an excitatory rebound. logical mechanisms. Then the experimental data which The landmark of arousal is a strong increase of the provide in the human suggestions on the regulation of excitatory response and a marked reduction of awakening, mainly those concerning sleep architecture the inhibitory phase, eventually with disappearance and homeostatic/circadian factors. These aspects will of the rebound [4]. be discussed also in a life span perspective. Age in fact is In all the thalamic nuclei sleep is signalled by a powerful factor which may in¯uence awakening. oscillatory rhythmical activity, synchronizing dien- Clinical contributions will examine two main sleep cephalon and cerebral cortex [1]. disorders: insomnia and hypersomnia. Daytime func- In acute experiments, in thalamic neurones intra- tioning in insomniac patients will be discussed too and cellularly recorded, a disruption of the oscillatory compared to other pathologies like sleep apnea. neuronal activity was observed during EEG desynchro- Dif®culty in waking up will be illustrated and discussed nization [5]. Spontaneous oscillatory activities in the linking pathologies to models of sleep regulation. thalamic neurones are controlled by the level of Finally, a contribution from the mind, i.e. psychological polarisation of the membrane potential. As has been factors in night awakening. This section will evoke links shown in in vitro preparations, all the thalamic neurones between some types of night waking and psychoana- behave like synchronized oscillators when they are lytic theory. hyperpolarized. In contrast, a reduction of the mem- brane polarisation induces an abrupt blockade of rhythmical activity and increase of responsiveness to peripheral input[6]. This is themechanism by which THALAMIC AND EXTRA- the ascending cholinergic pathways, originating from THALAMIC MECHANISMS IN the mesencephalon, are able to induce desynchroni- CORTICAL AROUSAL zation and arousal. However, experimental evidence shows that choli- Awakenings essentially constitute cortical arousal, but nergic cells are also located in the preoptic-anterior with a strong behavioral component. Here we shall hypothalamic and basal forebrain regions (BF-POAH) focus on the former. Cortical arousal, also called and project to the cerebral cortex. GABAergic activation, is revealed by electroencephalographic neurones have been recently discovered within the desynchronization and a general increase of electrical BF in the same regions where cortically projecting activity and excitability both in sensory and motor cholinergic neurones were described [7]. Neurons systems. located in these areas may in¯uence cortical activities Cortical arousal has been studied in animal models, through direct projections as well as indirectly through using chronic preparations, and it has been shown that sub cortical connections involving the medial and the they are controlled by various subcortical structures. dorsal thalamus. Dampening of the GABAergic inhibi- The ``activating system'' is constituted by neurons tory in¯uences ascending from these regions to the located in the midbrain reticular formation (MRF) thalamus and the frontal cortex could be one of the projecting to the thalamus and to the cerebral cortex mechanisms of cortical arousal. The cholinergic and [1]. In the thalamus, in many intralaminar nuclei non-cholinergic preoptic-anterior hypothalamic and AWAKENING FROM SLEEP 3 basal forebrain neurones are also under the control of combined information from the electroencephalogram endogenous , as was clearly shown in vivo and (EEG), electrooculogram (EOG) and electromyogram in vitro preparations [8]. (EMG) is used to separate behavioral states by Recently, in the thalamic nuclei, in chronic animal quanti®able criteria. While these criteria allow to preparations, has been described a very slow rhyth- distinguish sleep and wakefulness objectively, they mical activity, highly correlated with two major oscil- also show gradual steps of state transitions. There latory components detectable in the peripheral activity are atleast four different electrophysiological criteria of the sympathetic system, both in man and in animals. to de®ne transitions from sleep to wakefulness: In the EKG these very slow rhythms can be observed (a) intrusion of alpha activity, or an increase of higher as variability of R±R intervals and have been classi®ed frequencies in the sleep EEG, (b) EEG de®ned arousals as low (LF; 0.04±0.15 Hz) and high (HF; 0.15±0.5) [12], (c) epochs of wakefulness [13], and (d) full frequency in humans. The HF oscillation has been awakening. related to respiration, and is considered a marker of For young adults the percentage of time awake vagal modulation. The LF rhythm, related to vaso- during night sleep, according to electrophysiological motor activity, was proposed as a marker of sympa- criteria, is generally less than 5%. Williams et al. [3] thetic modulation. The origins of these oscillations can observed a mean value of 1.3% + 1.1% for 10 males, be attributed to the medullary neurones, where they and 0.5% + 0.5% for 11 females. In spite of their rare have been recorded in the areas involved in the occurrence, awakenings are events of major strategic regulation of cardiovascular system. In thalamic importance since they allow the sleeper to scan the neurons these very slow rhythms are in¯uenced by environment and to decide either to go back to sleep transitions of sleep±waking cycles. In most of somato- or to terminate sleep. Merica and Gaillard [14, 15], sensory thalamocortical neurones, studied by means of who analyzed the distribution of all stages in uninter- the spectral analysis of the spontaneous ®ring, arousal rupted and interrupted cycles of healthy adults des- is accompanied by a power shiftfrom HF toLF as cribed a peak of wakefulness early in normalized, the main component in very slow rhythms domain, uninterrupted NREM-REM sleep cycles, while the whereas coherence with the cardiac HF rhythms is lost distribution of wake episodes was irregular in a [9]. In man a very slow oscillation of EEG spectral subset of interrupted cycles. This ®nding was repli- power has been recently described, in the minutes cated and extended in a study by Schulz and Bes [16] domain, and attributed to a brain stem generator who analyzed a sample of 799 nights with a total of triggered by the arousal systems [10]. 3366 normalized NREM-REM cycles from 29 young, What recalled above shows that many subcortical healthy subjects, whose sleep was recorded for mul- components are acting during cortical arousal. tiple nights. Time awake peaked in the early part of the Thalamic activity is dependent not only by ascend- normalized cycles, i.e. immediately after the end of ing in¯uences from mesencephalon, butalso from REM sleep. The heightof thepeak increased mono- anterior hypothalamic and basal forebrain regions, tonically from cycle 1 to cycle 5. The peak value of time which could also act directly on the cortex. Possibly, awake was less than 3% in the ®rst cycle, 8% in more caudal brainstem regions, usually considered the second cycle, about 10% in the third, about 12% to be involved only in peripheral regulations, could in the fourth cycle, and 13±14% in the ®fth cycle. contribute to the overall changes of neocortical Additionally, the area under the curve of the wake activity during arousal. epochs increased in the ®rst 20%-proportion of the normalized NREM-REM cycle from the ®rst to the ®fth cycle, while it remained on a steady low level for the remainder of the normalized cycle time. Thus, awake- nings during sleep show a characteristic distribution THE TEMPORAL DISTRIBUTION with a local maximum immediately following REM OF AWAKENINGS sleep. Preferred transitions from REM sleep to wake- fulness have also been reported by Muzet et al. as early Sleep and wakefulness are conceived as two distinct as 1972 [17]. This in mind, it will be interesting to behavioral states which differ in body position, analyze the wake distribution in sleep cycles of patients muscular and neural activity, and consciousness. The with sleep disturbances to see whether their distribu- common research criteria to separate sleep and tion pattern of wake episodes represents an exagger- wakefulness are electrophysiologically de®ned. The ation of the normal pattern, or whether their wake 4 T. AÊ KERSTEDT ET AL.

Figure 1 times follow a different pattern which is more irregular preferred time to wake up from night sleep is phase with a random distribution across NREM-REM cycles. related to circadian rhythms and to the ultradian In this case, one may speculate that the low rate and REM-NREM . In a later study, which was typical distribution pattern of wake episodes in sub- conducted under forced desynchrony conditions, Dijk jects without sleep complaints has an adaptive value, and Czeisler [21] tried to assess separately the relative which is compatible with the ongoing sleep process, contribution of the circadian pacemaker and the sleep while longer and irregularly distributed awakenings homeostat to the consolidation of sleep. While high deteriorate sleep quality and possible also interfere sleep ef®ciency was maintained in the ®rst half of sleep with cognitive processes during sleep [18]. at all circadian phases, sleep consistency in the latter While the distribution of sleep interruptions by half of sleep depended on the phase relationship with wakefulness can be analyzed from sleep which was the circadian core body temperature cycle. Sleep was recorded under normal conditions, sleep termination severely disturbed when it coincided with the rising was preferably studied in polygraphic sleep recordings phase of the body temperature cycle, while wakeful- under experimental conditions without external zeit- ness within sleep remained at very low levels when the gebers. Under these conditions, where subjects deter- second half of scheduled sleep coincided with the mined the end of sleep by themselves, it was found that minimum of the circadian body temperature rhythm. the ®nal awakening preferentially coincided (a) with This suggests that the homeostatic component of sleep the rising slope of the circadian rhythm of deep body regulation dominates in the ®rst half of sleep, while the temperature and (b) with the REM sleep phase of consistency of sleep in the second half of sleep mainly the NREM-REM cycle [19, 20]. This indicates that the depends on circadian components, with a high rate AWAKENING FROM SLEEP 5 of intrusion of wakefulness into sleep or termination of awakenings within the ultradian NREM-REM sleep sleep coinciding with the rising limb of the circadian cycle was also reported by Merica and Gaillard body temperature cycle. [14, 15] for a subset of interrupted cycles under Another approach to study sleep termination in normal environmental sleep conditions. relation to preceding REM or NREM sleep was chosen The transition from the sleep into the wake state by Campbell [22] who analyzed spontaneous sleep can be measured by behavioral responses or by termination in subjects who were continuously recor- changes in the EEG power spectrum with a decrease ded for 60 h under restconditions.The analysis of delta and theta power on the one hand and an was con®ned to sleep episodes which were character- increase of alpha power on the other (Ogilvie and ized by the presence of both REM and NREM sleep. Simons [27]). The authors assume that ``the loss of Sleep termination data were compared to expectancy hypersynchronization, which begins rapidly at the point data which were either based on the overall REM and of waking and continues beyond it, is the most likely NREM percentages, or more conservatively on the explanation for the decreases in low frequency power'' proportions of REM and NREM sleep in the last third (p. 85) which is a hallmark of sleep termination. The of each sleep episode. Both comparisons showed speed of this transition has been studied in the context that the termination of sleep occurred signi®cantly of the sleep inertia concept [28]. The clear cut changes more often from REM sleep than would be expected in EEG frequency composition, which are related with by chance. Campbell found also that the mean duration the state transitions wake-sleep-wake, have also been of those REM episodes which were terminated used for the implementation of computerized methods by awakening was only half of those which were to detect episodes of wakefulness during sleep or sleep uninterrupted, suggesting that sleep termination did termination [29]. notfollow a completedREM sleep episode but A ®nal aspect of sleep termination is the expectancy rather interrupted REM sleep. This author suggested to wake up at a given time. Some people claim to be that REM sleep as a state with high neural activity very accurate in timing self-awakening [30]. In an provides ``optimal physiological conditions for the experimental study with actometric measures transition from sleep to waking'' (p. 241). The pre- Moorecroft et al. [31] found some indication for the ferred tendency to wake up out of REM sleep was also ability to self-awaken at a given time. An endocrino- shown for babies (Schulz et al. [23]) and young adults logical study by Born et al. [32] shed some lighton (Langford et al. [24]) while itwas notpresentin elderly additional factors which seem to be associated with the subjects with a mean age of 69 years (Salzarulo et al. expectancy to wake up at an anticipated time towards [25]). One may imagine different explanations for this the end of nocturnal sleep. The authors studied the age-dependent difference in the sleep stage association regulation of adrenocorticotropin (ACTH) release in of sleep termination. Either sleep is shallow and fragile association with sleep termination under three experi- in elderly patients, thus diminishing differences in mental conditions, an early planned awakening, a late arousability between sleep stages, or sleep in elderly planned awakening, and a surprise condition in which patients is less shielded against the intrusion of exter- sleep was terminated earlier than expected by the nal disturbances which may lead to arousals and subjects. The interesting ®nding was that the early awakening independentof theongoing sequence of awakening was preceded by a distinct increase of sleep stages. A more recent study by Murphy et al. [26] ACTH within the last hour before waking, while could help to clarify these different views. The authors, ACTH had a secretion surge only after sleep termi- who studied subjects in isolation from external time nation in the surprise condition, where subjects did cues found again that younger subjects (mean age: 22 not expect to be awakened at this time. Thus, the years) awakened preferentially from REM sleep while increase of ACTH some time before sleep termination older subjects (mean age: 68 years) did not. However, may be one of the adaptive mechanisms, which prepare those older subjects who had sleep ef®ciencies above the organism to transit from sleep into wakefulness the median were more likely to wake up from REM at the end of the subjective night. sleep than those with lower sleep ef®ciencies. The In summary, sleep-wake transitions are dependent results con®rm age-related differences in sleep ter- (a) on the circadian phase of the sleep episode with mination and suggest that sleep quality is a mediator more intrusion of wakefulness and a greater chance variable which interferes with the relationship for sleep termination in the rising phase of the between age and sleep termination, even under con- body temperature cycle, and (b) on the phase of trolled external conditions. An irregular distribution of the ultradian NREM-REM sleep cycle with a high 6 T. AÊ KERSTEDT ET AL. probability to wake up out of REM sleep. This latter conditions of spontaneous circadian resynchronisation factor seems to become effective at least early in during isolation experiments. There, the terminating development or in situations where the sleeper is force seems to be circadian±most sleeps tend to shielded againstexternalin¯uences, and zeitgebers, terminate on the rising slope of the temperature while its role may be negligible if sleep is fragmented rhythm, whereas the circadian trough is a zone of or unprotected against randomly occurring external ``forbidden'' awakening [38]. in¯uences. The transition from sleep into the wake In a study in which sleep was displaced to different state is heralded by adaptive mechanisms such as an times of the 24 h span (23:00 h, 03:00 h, 07:00 h, increase of ACTH, and itis accompanied by typical 11:00 h, 15:00 h, 19:00 h, and 23:00 h) with gradually EEG changes with a decrease of slow wave (delta and increasing time awake, it was demonstrated that the theta) activity and an increase of activity in the alpha circadian rise of rectal temperature was very closely frequency band. related to sleep termination. However, when sleep was started close after the circadian acrophase (i.e. at19:00 h) sleep durationexceeded 10 h and did not end until shortly after the circadian trough [39]. DISPLACED SLEEP AND Recently, Dijk and Duffy [40] have demonstrated the IRREGULAR HOURS sensitivity of sleep termination to the ®rst tendency to circadian upswing, immediately after the circadian If sleep architecture is one major regulator of awaken- trough. ings, the second major regulator probably is the timing In a series of experiments in which circadian phase, of sleep in relation to circadian phase and prior sleep. time awake or previous duration of sleep have been The effect is particularly visible in connection with varied, it was found that the time of day or circadian irregular sleep/wake patterns and when comparing phase had very strong effects, terminating sleep around such patterns with the reactions to day work. the circadian maximum [41]. These effects are, how- Most individuals with daytime work tend to use ever strongly modi®ed by prior time awake before the external means to wake up and terminate with some start of the sleep, as well as by the amount of prior subjective dif®culty and with considerable inertia in sleep. Thus, sleep loss will cause a resistance to the terms of performance [33]. Awakenings after staying circadian rise, delaying termination. This means that up very late, as after, for example, night work, tend to sleep will terminate as a compromise between the be spontaneous and ``easy'', but premature, as com- circadian and the homeostatic in¯uence. This observa- pared to night sleep [34]. Sleep is often reduced to tion is often more dramatic when sleep is started on 5±6 h. However, even if sleep is prematurely termi- the circadian rise. Then 8, 4, 2, and 0 h of prior night nated, it appears that it is not disturbed in the sense of sleep will cause sleep length to vary between 2 and 4, an increased number of awakenings. At the opposite 5 h [42]. In this study sleep was not terminated until the extreme, awakenings from sleep before an early start amount of spectral power density in the delta band of work are mostly forced through external means, as (0.5±2.5 Hz) had reached the low levels normally seen well as perceived as dif®cultand unpleasant[35]. around the termination of night sleep. Thus, it appears However, sleep length is often the same as after that the circadian rise is permitted to terminate sleep going to bed after night work. Awakenings after sleep only after the normal need for delta (stages 3 and 4) subsequent to an afternoon shift tend to be mixed but sleep had been obtained. During night sleep this level is to contain much spontaneous sleep termination. reached a few hours before ®nal sleep termination Similarly, aircrew travelling westward across several [43]. This may cause one to speculate that from a time zones will experience premature awakenings [36] homeostatic point of view night sleep termination is i.e. easy awakenings [37], whereas aircrew travel- unnecessarily late, very likely due to the sleep main- ling eastward will experience dif®cult and forced tenance effects of the circadian trough. awakenings [37]. Interestingly, the tendency to terminate sleep shows The reason for the different patterns of sleep the same circadian pattern as does the tendency to termination is the relative in¯uence of circadian and initiate sleep. That is, during daytime sleep will be homeostatic factors. However, the amount of data is prematurely terminated, while attempts to start a sleep rather scarce since few laboratory studies have per- episode will involve a long latency. At night, sleep mitted sleep to terminate spontaneously. Some infor- latency will be short, whereas sleep termination will be mation may be gained from awakenings under delayed [41]. AWAKENING FROM SLEEP 7

Considering the dif®culties of early rising and the resist the sleep terminating in¯uences of the morning circadian-homeostatic regulation of sleep termination, circadian upswing. it is not surprising to see that also performance on In summary, spontaneous sleep termination is awakening is considerably worse after awakenings at mainly dependenton thecombined effectof circadian the circadian trough [44] and after extended wakeful- and homeostatic in¯uences. The subjective dif®culty of ness [45]. In particular, late night during continu- awakening re¯ects the same factors ± the circadian ous wakefulness involve pronounced inertia in terms trough and sleep loss makes awakenings dif®cult and of performance and subjective feelings of sluggishness. non-spontaneous. The homeostatic and circadian regulation of the subjective ease awakening has an interesting bearing on other aspects of sleep quality. Thus, while it has been demonstrated that sleep termination is easier the AGE CHANGES closer to the circadian acrophase of body temperature [46], the feeling of being well rested is higher for Across the life span, night sleep undergoes several awakenings close to the acrophase. Intraindividual age-related modi®cations, extensively reviewed in correlation's showed that being well rested was largely a recentmeta-analysis[51]. These changes concern related to the ease of awakening. That is, unless the the vast majority of sleep parameters, e.g. sleep awakening was easy, one awoke with the impression of duration and the amount of REM and NREM sleep, not being well rested. The ease of awakening, further- and are particularly prominent during early develop- more, was closely related to the amount of stage Wake ment[52] and in elderly people [53, 54]. In healthy and lack of SWS, suggesting that poor sleep would individuals age is also an important determinant of often result in a feeling of being well rested, mainly sleep continuity, which has a major effect on sleep because the awakening was easy. quality and subjective performance during daytime The other leg of subjective sleep ratings, sleep [46, 55, 56]. quality, maintained a high correlation with sleep However, the age-related characteristics of spon- ef®ciency and SWS, which were the main predictors. taneous awakenings during night sleep as an event Thus, we quite frequently found weak negative corre- per se have only recently become a topic of discussion. lations between subjective sleep quality and being well It is well known that the night sleep of the healthy adult, rested. The two are clearly not the same thing. In fact, unless it is perturbed by pathologies (either medical or a good night's sleep seems to be dominated by SWS, neuropsychiatric) or by life and environmental circum- but ended by a certain amount of poor sleep to stances (time displacement of sleep), is characterised facilitate the awakening. The relation between the ease by very few interruptions [57]. This is not the case in of awakening and feeling of well-restedness is likely to the extreme ages, that is, infancy and old age. break down in insomnia patients, where is a All psychophysiological studies, regardless of differ- pronounced trait [47]. ences in instruments (direct observation, actigraphy, There is also a pronounced age effectin theease of polygraphy) or methodology (time criteria to de®ne awakening and in feeling well rested after sleep [48]. behavioral awakenings, ranging from 1 to 5 min), are Somewhat unexpectedly well-restedness improved consistent in ®nding that the frequency of awakenings with age, at least up to 65 years, which was the in infants is higher than in young adults [58±60]. upper limit in this study of gainfully employed indivi- There have been attempts to look deeper into the duals. Again, this feeling was correlated with an ease developmental course of spontaneous nocturnal awa- awakening, and with disturbed sleep. As with insomnia kenings atearly ages. Giganti et al. [61], in a preliminary patients the relation probably breaks down in the study on pre-term infants, showed few changes in the elderly, but this has not been the subject of investiga- number and duration of awakenings between 34 weeks tion yet. In the study cited it was suggested that the and the term. After term a pronounced reduction in bene®cial effects were due to the greater degree of the number of night awakenings goes along with the diurnal ``morningness'' that increases with age [49]. increase in the duration of night sleep episodes [62]. This effect, in turn, may be due to an increased This trend is particularly evident across the ®rst year of sensitivity to the circadian upswing during the day life [58], with a particular evidence in the second [40]. Interestingly, the dif®culties maintaining day sleep semester [60]. By contrast, the duration of the after night work increase with age [50], probably also awakenings, that is, the time spent awake before re¯ecting a decreased ability of the sleep mechanism to sleep re-onset, remains constant all along the ®rst 8 T. AÊ KERSTEDT ET AL. year of life [60]. By the end of the ®rst year of life, night were notevaluatedin Hume et al. study, but Webb's sleep is already much less interrupted than at birth: data [73] indicate that they might have turned out to be thereafter, the decrease in the frequency of awaken- in¯uenced by such an interaction. ings continues at a slower rate [63] until it reaches Another interesting example of the different values notfar from adulthood. psychophysiological features of infants' and elderlies' Williams et al. [13] suggested that the number of awakenings regards the state of sleep, which precedes awakenings starts to increase again already at mid-age: them. In infancy, most of the awakenings emerge from they showed that both women and men in their forties REM sleep [23], although the difference in the likeli- woke up during night sleep more often than women hood of awakening from the two states is reduced and men in their thirties. This evidence was con®rmed after the sixth month [60]. It has been proposed that in a study on 400 adults aged from 20 to 70 based on also in the young adult REM sleep would have a ``gating'' sleep logs and actimetry [64]. Also, a slight trend to an role for both ®nal awakening [19] and awakenings increase in the frequency of awakenings was found in during sleep [75]. In the elderly, instead, no prefer- a sample of Japanese workers in the age range between ential association was observed between REM sleep 19 and 64 years [65]. and awakenings, whereas awakenings from Stage 2 Several investigations have reported that in elderly were more common [25]. For this reason, both in individuals the number of awakenings increases again infants and in the aged, there is a coincidence between [66±68]. Awakening atnightis one of themost the sleep state following and the one common complaints in subjective sleep diaries of preceding awakening: however, this is REM for the general population elderly people [69, 70], and is the former and NREM for the latter. Also, the time widely reported also by healthy old subjects. distribution of the awakenings have a peculiar feature Thus, if we only take into account the number of in infants, with the gradual build up of a periodicity awakenings, as an index of the sleep consolidation which is around 100 min by the end of the ®rst year of process, we may describe a curvilinear trend with life [60]. a steep descending slope in the ®rst year of life, a low It is plausible that the changes in the pattern of plateau level across childhood/young adulthood and an awakenings, from infancy to adulthood, up to the ascending slope thereafter, slowly rising in late adult- elderly, may re¯ectdifferentpsychophysiological pro- hood and progressively becoming steeper with age. cesses. During early development, the high number As a result, infants and elderly subjects tend to wake and the short duration of awakenings are due to an up with similar frequency during the night: however, it inability to sustain prolonged and stable states [76] would be hazardous to interpret the two ages as i.e., infants wake up several times per night as a re¯ec- similar to each other. tion of their polyphasic sleep-wake rhythm, but rapidly First of all, a longer duration of the wakefulness fall asleep again since they are unable to sustain following awakenings has been found in old subjects wakefulness. [71, 72]. In an assessmenton 25 individuals aged Together with the evidence that successive between 60 and 75, whose mean number of night sleep bouts have a similar internal architecture [77], awakenings was 3.9, our group detected a particularly the rather stable features of night sleep interruptions impressive latency to sleep re-onset, much longer than in infants suggest that they may represent ``®nal in infants and young adults, also resulting in a signi®- awakenings'' of each sleep bout. The consolidation cantly higher amount of intra-night wakefulness [25]. with time of both night sleep and day wakefulness Secondly, a peculiarity of the frequency of awaken- [62, 78] could be interpreted as due to the interaction ings in older persons concerns the appearance of of the emerging homeostatic factors and of the circa- wider gender differences. In a study by Webb [73] on dian drive. healthy individuals between the ages of 50 and 60 Elderlies' awakenings, instead, seem to be the years, women reported more frequent awakenings, expression of a disorganisation of sleep. First, the inconsistent with the evidence of the objective record- occurrence of frequentawakenings neitherpreferen- ings showing twice the level of sleep interruptions tially associated to REM sleep nor to NREM sleep, is in men. likely to imply a marked dif®culty in sleep maintenance. It is worthwhile noticing that in a study over the In addition, the impressingly long time spent awake adultlife-span (20±70 years), Hume et al. [74] found no after each awakening speak also for an impairment of ``age-gender'' interaction for any sleep measure but the sleep re-onset process. Age-related changes in sleep onset and wake-up time. Awakenings features circadian rhythms have been often invoked to explain AWAKENING FROM SLEEP 9 the marked increase in the drive to wakefulness during INSOMNIA nightsleep. These circadian modi®cations,possibly connected to the changes of many biological rhythms Insomnia has been historically de®ned by patterns of (core body temperature, GH, testosterone, prolac- inappropriate wakefulness which occur during the tine, progesterone and cortisol secretion), as well as to sleep period. Patterns of arousals, awakenings, morphological and functional changes shown in the and wakefulness may also help de®ne patients with suprachiasmatic nuclei and in the pineal gland [79], insomnia versus excessive sleepiness clinically [86]. include the decrease in amplitude, the phase advance Insomnia may be primary or secondary to many and the shortening of the period. The latter has been medical conditions [87]. Primary (or psychophysio- widely documented for body temperature [80, 81], but logical) insomnia is de®ned as dif®culty falling asleep or is not univocally reported with regard to the free- maintaining sleep not secondary to any other medical running rest-activity rhythm. If animals and early problem or . As such, the de®ning factor humans studies have indicated a shortening with age, is increased wakefulness. Insomnia is commonly Dijk and coworkers, studying circadian sleep regu- de®ned as either a sleep onset problem or a sleep lation in the elderly by means of a number of experi- maintenance problem. However, little work has sys- ments based on the ``forced desynchronization'' tematically looked at patterns of wakefulness and protocol [40, 82], did not ®nd any shortening of the arousal in insomnia patients. In the discussion which circadian period for the sleep-wake rhythm. Instead, follows, awakenings, arousals and wakefulness during a reduced strength of the circadian signal favouring sleep are all de®ned based upon EEG criteria. Unless sleep in the early morning hours was identi®ed. The noted otherwise, awakenings were based upon 30 s Authors hypothesize that a factor mediating this epoch scoring using Rechtschaffen and Kales criteria, reduction is the empoverishment of wakefulness consists of all wake time after the ®rst activity, which is supposed to act with a sleep-maintain- sleep onset, and arousals were scored based upon the ing role [83]. Furthermore, the propensity to awaken ASDA criteria [88]. from sleep advances relative to the body temperature Early studies which looked at awakenings in patients nadir in older people, a change that is opposite to the reporting insomnia found that the number of awaken- phase delay of awakening relative to internal circadian ings (1-min criterion) was increased [89]. However, rhythms associated with morningness in young people. such studies predated standard polysomnographic As a consequence, older people appear to have great screening of insomnia patients for periodic limb move- dif®culty in sustaining sleep after the temperature ments and sleep apnea. The inclusion of even a few nadir. patients with sleep apnea or periodic limb movements Also homeostatic changes seem to contribute to the in a group of psychophysiological insomnia patients age-related changes in awakening features. The modi- would resultin theappearance of many more arousals ®ed sleep behaviours over the 24 h, with frequent and awakenings [86]. As a result, it is still common for napping and reduced physical and mental activity, could reviewers to conclude that patients with primary sleep cause, according to the homeostatic component of the maintenance insomnia show both an increased number two-process model of sleep regulation [84], a reduc- of awakenings and longer duration of awakenings [90]. tion of the sleep pressure in elderly compared to However, more recentdatado notsupportincreased young subjects. This might partly explain the longer total awakenings in patients with psychophysiological sleep latency, the decreased SWS, the higher degree of insomnia [91±93]. sleep fragmentation, and above all the dif®culties falling In three studies done with groups of age, sex, and asleep again after each awakening. weight matched primarily sleep maintenance psycho- Although both the circadian and the homeostatic physiological insomnia patients and normal sleepers regulation seem to be affected by elderliness, we can [91±93], consistent signi®cant increases were found agree with Wauquier and Van Sweden [85] that it is for sleep latency and wake time during sleep in the not yet possible to indicate which one between insomnia patients as compared to normals as expected. process C and process S is primary or secondary. Of interest was the fact that the number of awakenings Furthermore, irrespective of changes in sleep regula- was not signi®cantly greater in the insomnia groups tion, the higher propensity to awakenings of elderly compared to their matched normals. Similarly, a study people may as well be the result of anatomical and of geriatric insomnia patients and matched geriatric functional de®cits impairing their capability to generate normal sleepers reported the same result [94]. The and coordinate stable sleep patterns. arousal index was actually nonsigni®cantly greater in 10 T. AÊ KERSTEDT ET AL. the normal groups than in the matched insomnia Of particular interest is that the sleep apnea patients groups in two of the studies, although no signi®cant did not differ signi®cantly from the insomnia patients in differences in arousal index were found in any of the sleep latency or in wake time after sleep onset experiments. This implies that insomnia patients have although apnea patients report signi®cant sleepiness longer awakenings. When the data were examined, it during the day while the insomnia patients have great was found that the insomnia patients did have longer dif®culty falling asleep during the day. One of the awakenings (about3 min on average) as compared to largest differences between the groups was in the normal sleepers (about 1.4 min). This indicates that arousal index. Sleep apnea patients also had greatly sleep maintenance is not the problem in psychophysio- increased awakenings, butthisdifference was not logical insomnia. Rather, these insomnia patients signi®cant due to very large variability. Patients with always have dif®culty falling asleep whether it be at sleep apnea have many shorter awakenings and bed time, during a daytime , or after an awakening frequent arousals, compared to insomnia patients during the night. (awakenings averaged about1.5 min in sleep apnea In addition to number of awakenings, the distribu- patients and arousals averaged about 1 per min tion of wakefulness across the night in matched groups throughout the night). of insomnia patients and matched normal sleepers was The high rate of arousals and awakenings produces examined in one data set [92]. Obviously, the insomnia sleep fragmentation and decreases the restorative patients had more wake time than the normal sleepers. function of sleep [96]. Because patients with psycho- The increased wake time was relatively evenly distri- physiological insomnia have an arousal index that does buted throughout the night in the normal sleepers but not differ from that seen in normal young adults, they was relatively increased in the insomnia patients in the are less prone to suffer from nonrestorative sleep. ®rst two-thirds of the night. The patients with insom- In fact, in one study, the pattern of awakenings and nia had 48% of their total wake in the ®rst third of arousals seen in actual psychophysiological insomnia the night (normals had 40%); 34% of their total wake in patients was produced in normal young adults for the second third of the night (normals had 28%); and 1 week (by using tones to awaken or arouse the 18% of their total wake in the ®nal third of the night normals at the same times that the insomnia patients (normals had 33%). had awakenings or arousals) with relatively little Total sleep time is reduced in patients with psycho- impact upon the normal sleepers [92]. As such, the physiological insomnia (itaveraged about6.4 h in the pattern of longer awakenings with infrequent arousals studies cited above compared with 7.3 h in matched found in insomnia patients appears to preserve normal sleepers). Patients with other sleep disorders sleep restoration in comparison with the more who have similar reductions in total sleep time typically frequent arousal pattern seen in patients with are sleepy during the day. One difference is that sleep apnea. patients with either obstructive or central sleep apnea One other summary paper reported awakenings or periodic limb movements during sleep have a very and stage shifts in normal sleepers, insomnia patients, different pattern of arousals and awakenings during the and patients with sleep apnea [97]. Comparisons to the night. For example, a group of patients with periodic other studies are dif®cult because sleep stage data limb movements had a total sleep time of 6.7 h but had were notpresented,1 min scoring epochs were used, 28 awakenings and an arousal index of 30 (compared and subjects in the insomnia and apnea groups were to an arousal index of 16 in the insomnia studies cited older than the normal group. The results differed above) and excessive sleepiness [95]. primarily in that Declerck et al. [97] found very few A random group of 10 patients with sleep apnea awakenings in their normal sleepers. Their very low were selected from our clinic population (with the number of awakenings probably resulted from the fact constraint that age would be about the same as the that they used a 1-min scoring epoch (and normal insomnia patients) so that patterns of arousal and sleepers typically have short awakenings while insom- awakening in obstructive apnea patients could be nia patients have long awakenings) and the fact that compared with those patterns in patients with psycho- their normal sleepers appeared to be younger than the physiological insomnia. Sleep and arousal data averaged insomnia patients. Declerck et al. [97] found a similar from the three insomnia studies discussed above and number of awakenings in their insomnia patients and in from the patients with sleep apnea are presented in their sleep apnea patients. They do not present data on the table. It can be seen that there are a number of the severity of apnea in the apnea patients, but since signi®cant differences in sleep in these two groups. awakenings were also shorter in apnea patients than in AWAKENING FROM SLEEP 11 insomnia patients, the length of the scoring interval awaken to the ringing of an alarm clock and if the could also accountfor this®nding. ringing is prolonged they turn it off and return to sleep In summary, insomnia is de®ned by increased wake- so that they have to be awakened by family members fulness during the night. Patients with insomnia have or friends. Awakening procedure has to be vigorous more dif®culty falling asleep as a characteristic trait. As and repeated. Once out of bed subjects are still such, psychophysiological insomnia patients take confused, very slow, unable to react adequately to longer to fall asleep after awakenings during the night external stimuli and it may take up to several hours and therefore accumulated more wake time during the before they can function adequately. Investigation of night. However, recent data suggest that these patients these subjects has somewhat turned short in the past. may nothave increased awakenings and arousals The multiple sleep latency test (MSLT) seems irrele- during the night as do patients with sleep apnea or vantor atleastinsuf®cientfor several reasons. periodic limb movements [91, 93]. Awakening the subject early in the morning for the MSLT precludes documentation of the prolonged night time sleep, and the MSLT procedure precludes the IMPAIRED AWAKENING IN observation and recording of prolonged, unrefreshing SLEEP DISORDERS MEDICINE daytime sleep episodes. Moreover the mean sleep latency is not strikingly reduced as it is in or (INSOMNIA EXCLUDED) severe sleep apnea syndrome. Hence the need for more adequate investigations. Most healthy subjects can move, think and react Continuous has the advantage appropriately within seconds or at most minutes of documenting the total duration of spontaneous after the cessation of sleep, regardless of whether sleep and thus of giving a more realistic picture of sleep awakening is spontaneous or provoked. However, behaviour in these subjects. Along this line 19 subjects there are different instances of pathological dif®culties with the polysymptomatic form of idiopathic hyper- achieving normal awakening: either after provoked somnia, 11 females and 8 males, aged 18±57 (median awakening ata timewhich is generally considered as 27) underwentpolysomnography. Night1 was a con- normal, for instance at the end of the night, between ventional night with lights off at 22:30 and lights on at 6:00 and 9:00 a.m.; or after provoked awakening during 7:30, followed by a MSLT; night2 and day 2 (18:30± naps supposed to be refreshing; or after spontaneous 18:30 the next day) served for continuous polysom- arousal in the ®rst third of the night. This chapter will nography with the subject free to lie in bed, sit at a summarize clinical features and results of laboratory table or make a few steps in the room at his own tests in each of these situations. convenience. Results are disclosed on Table 2. From these results Dif®culty achieving normal awakening it is clear that subjects did not show a severe propen- after provoked awakening at the sity to fall asleep (mean sleep latency ˆ 10.4 + 3.8). On the other hand total sleep time on night 2 and on end of night sleep night 2 and day 2 was extremely prolonged thus showing an enormous propensity of these subjects to Idiopathic hypersomnia has been ®rst described by sleep or an inability to terminate sleep. Yet this pro- Roth et al. [98] and Roth [99, 100]. It can be either cedure investigated sleep rather than awakening hence polysymptomatic or monosymptomatic. The poly- the need to resort to other strategies. symptomatic form is the best identi®ed one with According to the two-process model of sleep a prolonged major sleep episode, greatdif®culty regulation the dif®culty to achieve normal awakening waking up in the morning or at the end of a nap, could be the result of any combination of prolonged constant or recurrent sleepiness and unrefreshing decline of process S, delayed or insuf®cientrising of naps. In comparison the monosymptomatic form is process C or abnormality of process W. not as well characterised with a major sleep episode of To date the homeostatic process in hypersomnia normal duration, no dif®culty waking up, constant or patients has not yet been investigated. Results of recurrentsleepiness, refreshing or non refreshing a recent study of both melatonine and cortisol secre- naps. The great dif®culty waking up in the morning or tion in idiopathic hypersomnia are indicative of a phase after a nap, also referred to as sleep drunkenness, is delay of melatonine and cortisol rhythms in this typical of the polysymptomatic form. Subjects do not condition [101]. Finally Sangal and Sangal [102] used 12 T. AÊ KERSTEDT ET AL. cognitive evoked potentials (P300) measures and the exception of the ®rst short nap which was not showed that subjects with idiopathic hypersomnia followed by sleep inertia. Sleep inertia was maximum had longer auditory P300 latency than normals and after arousals from stages 3 and 4 NREM sleep. smaller auditory P300 amplitude than narcoleptic Conversely sleep inertia was completely absent fol- patients, e.g. cognitive evoked potential evidence of lowing the single long nap. cognitive dysfunction. Delayed sleep phase syndrome Dif®culty achieving normal awakening Delayed sleep phase syndrome is a disorder in which after spontaneous arousal in the major sleep episode is delayed in relation to the the ®rst third of the night desired clock time [103]. It is characterized by Arousal disorders: confusional arousals, sleep walking sleep-onset and wake times that are much later than and sleep terrors are three different desired, little or no dif®culty in maintaining sleep once grouped together because impaired arousal from sleep has begun, extreme dif®culty awaking at the stages 3 and 4 has been postulated as a common desired time in the morning, and a relatively severe to cause [106]. Confusional arousals occur during and fol- absolute inability to advance the sleep phase to earlier lowing arousals from stages 3 and 4 NREM sleep, most hours by enforcing conventional sleep and wake times. commonly in the ®rst third of the night. Sleep walking When patients are recorded at a conventional time consistsof aseriesof complexbehaviorsinitiatedduring (23:00±7:00) the sleep latency is prolonged and the stages 3 and 4 and sleep terrors manifest as a sudden patients experience dif®culty in awakening. A multiple arousal from stages 3 and 4 accompanied by autonomic sleep latency test performed after such a sleep period and behavioral manifestations of intense fear. Patho- can show shorter sleep latencies in the morning naps physiologically these entities represent incomplete compared to the afternoon naps [11]. awakenings from sleep, mostcommonly deep NREM sleep, leading to intensi®cation of the normal period of sleep inertia before full wakefulness is evident. Dif®culty achieving normal awakening In conclusion, dif®culty achieving normal awakening after provoked awakening during is a feature of different sleep disorders. However not naps supposed to be refreshing: a single mechanism seems to be involved. In idiopathic the example of narcolepsy hypersomnia the great dif®culty waking up comes after a very long period of sleep, and may be explained in Narcolepsyischaracterisedbyasetofclinicalsymptoms terms of either abnormal homeostatic or circadian including abnormal sleep features, excessive daytime process of sleep. In the sleep delayed phase syndrome sleepiness, overwhelming episodes of sleep, hypnagogic the dif®culty waking up is clearly related to an abnor- hallucinations, disturbed nocturnal sleep and manifesta- mality of the circadian rhythm of sleep which is phase tions of paroxysmal muscle weakness, and delayed and the time of provoked awakening does not . Characteristically patients wake up correspond to the normal time of awakening for these refreshed attheend of overwhelming episodes of subjects. In narcolepsy the dif®culty waking up is sleep and there is a refractory period of one to several a typical manifestation of sleep inertia, maximum hours before the next episode occurs. Because of this after arousals from stages 3 and 4 NREM sleep, but feature short daytime naps evenly distributed through- also present after arousals from stage 2 NREM sleep. In outthedayarerecommendedasatherapeuticmeasure. NREM sleep parasomnias, the so-called disorders of However one study [104] found evidence for sleep arousal, the dif®culty coming to complete awakening is inertia following brief episodes of drowsiness and light obviously linked with a spontaneous and incomplete sleep. A later study of scheduled naps and performance awakening from stages 3 or 4 and sets the stage to [105] was designed both to investigate the ef®ciency of abnormal autonomic nervous system changes and napping strategies in narcolepsy and to investigate skeletal muscle activity. sleep inertia effects associated with daytime naps. This study included ®ve short naps spaced equidistantly Oneiric activities versus dreams in throughout the waking period or a single long after- nocturnal awakenings noon nap scheduled 180 degrees out of phase with the nocturnal midsleep time. Most interestingly short naps The sleep disorders clinic can in a sense, be viewed as were accompanied by sleep inertia in narcoleptics with a clinic of nocturnal awakenings. Within the framework AWAKENING FROM SLEEP 13 of sleep disorders, nocturnal awakenings (or sleep- representation ...). Freud calls `` work'' the stallings) vary greatly. To examine sleep disorders from psychic mechanisms of transformations through the angle of nocturnal awakenings one needs to con- which is performed the passage of the latent content, sider the physiological components of sleep as well as the thoughts of the dream, to the manifest content,the the mental processes which accompany them. We will recall (or the report) of the dream after the night concentrate on the adult patient's mental sleeping [120]. Freud distinguishes between three mental content. We will choose for our case two opposed systems: Conscious, Preconscious and Unconscious, groups of awakenings: due to anxiety or with shields ± protective ®elds ± separating them. His post-traumatic dreams, and night terrors and sleep- topographic-economic model is a logical outcome of walking. Here we refer to a review of the literature the application of the method of free-association to the and to our clinical personal experience since 1971 with analysis of dream experiences [120, 121]. This method patients treated at our sleep disorders center. followed a fundamental rule: the patient had to say In this chapter we intend to show that dealing with whatwas passing throughhis mind, however absurd, patientswiththesesleepdisordersisdealingwithvarious immoral or painful itseemed. types of psychic activities: some are dreams (a speci®c We would picture the situation which leads to the form of thinking), some are not dreams, which we will formation of dreams as follows: Dreams accomplish call ``oneiric'' for lack of a better word. Oneiric experi- a function of guarding sleep. Dreams allows the sleeper ences, as we will see, are psychic activities which do to continue sleeping while playing with a pair of notfollow theclassical Freudian dream model. opposites: the wish to sleep versus unconscious A simultaneous examination of the way in which wishes (latent thoughts). The dream ®nds its energy, psychoanalysts take interest in sleep and in the sleeping its source, from the strength of unconscious wish. The mind, and of the clinical approach of con¯ict is between the wish to sleep and the wishes or could be useful. Clearly, a study of the psychoanalytical affects which threaten to waken the sleeper. Dream is point of view of the sleeping mind must also take into the guardian of sleep, but to be this guardian it must accountcurrentknowledge on sleep neurophysiology also guard itself: protect the global sleep. If the dream is [107, 108] as well as on mental processes during sleep disturbed, the dream disrupts sleep. Thus, the hallu- and upon awakening from differentstages[109, 110]. cinatory reinterpretation, distorting and deforming As our subjecthere is sleep pathology,we will only elaboration, builds up a facËade to the dream. recall in a few words that experimental and cognitive Through the work of the dream, the psychical activity psychology investigations, on dream-sleep-memory of the sleeper changes and transforms itself, but does relationships, have shown that mental activity not stop. The censorship holds the dream, which the continues throughout all sleep stages, all night long quietude of sleep and prevent the irruption of anxiety. [111, 112]. Psychophysiological research ®ndings indi- Out of this model, we will use only the description cate that dreaming occurs in all sleep phases and not of the mechanisms of dream formation, in other words only in REM episodes [113±118]. The mental activities the explanation of the dreaming production and we of sleep varies within sleep stages and with the time of will stay away from dream interpretation. night. With different rates of recall, and under diverse As we saw above, the mind never rests during sleep. guises, dream reports can be obtained througout all However, this does not mean that mental events sleep stages after awakening the subject. during sleep are always organized to form a dream. The classical Freudian dream work mechanisms. Freud's The dream is not the sole psychic activity of the works have been reconsidered in the light of present- sleeper. Thus, within the ®eld of clinic of awakenings, day neurobiology [119, 108]. They have come under dreams (here illustrated by nightmares), and oneiric hard criticism. Yet for example, the creation of activities (night terrors and serving as exam- Neuro-Psychoanalysis, ``An interdisciplinary Journal for ples) need to be carefully identi®ed [122]. The use Psychoanalysis and the Neurosciences'', shows how made of the word oneiric refers to mental activities interesting and lively is the discussion. experienced during sleepwalking or nightterrors, We will intentionally simplify the summary of the which are well-known nosological entities in the ®eld psychoanalytical arguments. The freudian theory, a cog- of sleep medicine. nitive description of the psychic processes, taught us In dream-anxiety attacks and post-traumatic night- that dream is the product of a work of transform- mares, true dreams are experienced. The , ational processes of thoughts, which use different a frightening dream with a feeling of a lived-in situation mechanisms (displacement, condensation, pictorial that awakens the sleeper, generally arises from REM 14 T. AÊ KERSTEDT ET AL. sleeporfromstage2oftheendofthenigh.Awakenedby The main point is that the intrapsychic state of a nightmare, the patient is fully awake and completely the sleeper suffering from one of such arousal dis- conscious with immediate dream recall. ``Exiting'' from orders does notallow thesame work of psychic sleep does notpose any problem [123, 124]. elaboration as with classical dreams [122, 133]. The Traumatic nightmares and sleep disturbances are structural organization of mental experiences, clinical effects of major stressing events [125]. The although assessed on an intuitive basis of clinical dream replays the traumatic event over and over again, observations, seems to indicate that the cognitive with a heavy emotional load and a corporal partici- features of mental production (less effective informa- pation, causing awakeness in terror, with conscious- tion processing) vary with respect to the situation of ness, and without amnesia. Post-traumatic nightmares, a nightmare production. occur mainly outside of REM sleep, sooner (1:00±3:00 Seen from the angle of psychoanalytical processes, a.m.) than typical anxiety dreams [126±128]. the hallucinatory mechanism is short-circuited; sleep Dreaming is one of the most complex forms of terrors and sleepwalking episodes are the result of an life and should notendanger sleep, butpreserve it extensive rupture of the protective barrier mechanisms [120, 121]. However, a nightmare, a proper dream, (psychological formations seen as a number of ®lters) fails to contain the emotional surge and to maintain, into and out of the Unconscious [134 ±136]. There is at the same time, the continuity of sleep and the absolutely no dream-work involved in these disorders. sleeping psychical life [122]. From Freud's structural They are not dreams, but oneiric activities. Such model of sleeping mind, nightmares are a failure of the oneiric activities are not experienced as a dream. normal pattern of dream, located at the border It seems that, in the case of a nightmare, dream- between Unconscious and Preconscious systems. anxiety attacks or post-traumatic nightmares, the The dreamed psychic situation becomes incompatible dreamer cannot continue his hallucination and with sleep. The dreamer cannot ``keep'' his halluci- cannotescape from awakening, when in sleep terror nation and is no longer capable of continuing to use or in sleepwalking the sleeper cannot escape from dream mechanisms. Awakening ends dreaming and sleep; the work of psychic elaboration here follows the sleep episode. other standards than classical dreams. Both cases end Sleep terrors and sleepwalking are much less frequent in awakening, but the dynamics of each are completely (but similar) in adults than in children. These disorders different: their mechanisms are diametrically opposed. are related to a disorder of arousal [106, 129]. They Most likely, these two types of disturbances are even occur at precise times, out from the deepest NREM incompatible: they are both very rarely found together sleep (a shift from stage 4 to arousal), early at night, in the same patient. with increased motor tone or motor activity. Sleeep is pertubed but not to the extent of full awakening. There is a severe cognitive dysfunction and no conscious Practice Points awakening. In other words, sleep will not give way to 1. Human subjects awake preferentially at the end wakefulness (the ability of the sleepwalker to fall asleep of REM sleep and the preparedness to awake soon after an episode, without reaching alertness at increases with the rank number of the sleep any point, is striking). cycle and with higher position of the circadian Adultsleepwalkers usually have some vague mem- morning upswing of the body temperature ories, the contents of which usually concerns a theme rhythm. Elderly awake from REM as well as of imminent catastrophe with a need to escape, or a from NREM sleep and earlier since the nadir of suggestion to move [130]. In sleep terror, mental the temperature. content report, hard to verbalize, is made of a single 2. Awakenings after day sleep ®nished in the early unelaborated scene which lacks human beings; gener- morning is usually the most dif®cult and those ally there is a lone terrifying vision accompanied by during the day time the easiest. intense anxiety [131]. 3. Insomnia patients differ from normals in the As Jouvetwrote[132]: `` ...sleepwalking is a good amount of total wake ± not the number of example of lack of psychoneural correlation which awakenings. could call the neurobiologist to more humility'', adding 4. Sleep inertia is abnormally strong in subjects further: ``Neurobiology (and specially clinical neuro- with the polysymptomatic form of idiopathic physiology) must admit that the relations between hypersomnia. sleep and conscience are ambiguous''. AWAKENING FROM SLEEP 15

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