False recalls, but not false recognitions, at the DRM paradigm are increased in subjects reporting insomnia symptoms: An online study.

BACKGROUND: In insomnia, poor sleep is accompanied by several cognitive impairments affecting prefrontal functioning that could affect source-monitoring processes and contribute to false memories production. By using a modified version of the Deese-Roediger-McDermott paradigm (DRM), we previously found that individuals suffering from insomnia produced more false memories than good sleepers adopting a free-recall task, especially for sleep-related stimuli. However, whether poor sleep affects false memory production in a task-dependent manner (i.e., free recall or recognition) remains unclear. METHODS: Through an online research method, we adopted the classical DRM paradigm to investigate the production of false recalls and false recognitions in 32 subjects referring insomnia symptoms (IN group) and 37 good sleepers (GS group), addressing also executive functioning and source monitoring ability in both groups. RESULTS: Compared to the GS group, the IN group produced more false memories (p = .002) and intrusions (p = .004) at the free recall task and showed a lower working memory index (p = .008). No between-groups differences emerged at the recognition task. Correlational analysis revealed significant associations between DRM performance, executive functioning and source monitoring (SM) variables. Moreover, false recalls were predicted by being in the presence of insomnia symptoms (p = .012) and intrusions by the number of correct responses to the Stroop task (p = .051) and SM task (p = .015), as well as by the presence of insomnia symptoms (p = .003). CONCLUSIONS: Our data show that the presence of insomnia symptoms can influence false memories production. Furthermore, the evidence that free recall is more affected than recognition suggests that poor sleep mainly affects performance at more cognitively demanding tasks. Finally, correlational and regression analyses support the hypothesis of a link between false memories production and both the presence of insomnia symptoms and executive functioning impairments.

Sleep and psychological characteristics in habitual self-awakeners and forced awakeners.

Previous studies described the modifications of physiological and behavioural variables associated with self-awakening, while only few studies assessed subjective sleep quality and psychological characteristics in habitual self-awakeners. Here we investigated self-reported sleep habits and features, as well as psychological variables of habitual self-awakeners and forced-awakeners, with special regard to subjective sleep quality, personality characteristics, anxiety and depression symptoms. In our sample, the prevalence of habitual self-awakeners was 15.1%. Compared to forced-awakeners, habitual self-awakeners showed more regular sleep/wake schedules and were more frequently morning types. Moreover, habitual self-awakeners referred to be more satisfied about their sleep, to wake up more easily in the morning, to need less time to get out of bed and to feel more refreshed upon awakening than forced-awakeners. We also observed an association between the habit of self-awakening and the "ability" to set the awakening to an unusual time. Concerning psychological features, habitual self-awakeners showed higher scores in Conscientiousness and Openness and lower scores in Extraversion compared to forced-awakeners, whereas no differences between groups emerged for anxiety and depression levels. In conclusion, our findings point to an association between the habit of self-awakening and good subjective sleep quality. In this perspective, future research should objectively test in detail the effects of the self-awakening habit on sleep structure and organization, taking into account also microstructural sleep features.

The effects of pre-sleep learning on sleep continuity, stability, and organization in elderly individuals.

Several studies have consistently shown that pre-sleep learning is associated to changes of sleep structure. Whereas previous research has mainly focused on sleep states, namely REM and NREM amount, very little attention has been paid to the hypothesis that pre-sleep learning might improve sleep continuity, stability, and cyclic organization, which are often impaired in aging. Thus, aim of this research was to assess, in a sample of 18 healthy elderly subjects, whether a memory task administered at bedtime would determine changes in any sleep parameter, with special regard to sleep continuity, stability, and organization. To this purpose, a baseline sleep (BL), i.e., a normal sleep with 9-h time in bed (TIB), was compared to a post-training sleep (TR), with the same TIB but preceded by an intensive training session. For the latter, a verbal declarative task was used, consisting in learning paired-word lists, rehearsed, and recalled for three times in a row. To control for individual learning abilities, subjects were administered several sets of lists with increasing difficulty, until they reached an error rate ≥20% at third recall. Relative to BL, TR shows a significant reduction in the frequency of brief awakenings, arousals, state transitions, "functional uncertainty" (FU) periods, and in the percentage of time in FU over total sleep time (TST). A significant increase in the number of complete cycles, total cycle time (TCT), and TCT/TST proportion was also found. All these changes are evenly distributed over the sleep episode. No sleep stage measure display significant changes, apart from a slight reduction in the percentage of Stage 1. Scores at retest are negatively correlated with both the frequency of arousals and of state transitions. Our data suggest that pre-sleep learning can yield a beneficial re-organizing effect on elderlies' sleep quality. The inverse correlation between recall scores and the measures of sleep continuity and stability provides further support to the role of these features in memory processes.

[Prevalence of community-acquired methicillin-résistant Staphylococcus aureus]. / Etude de la prévalence de la résistance à la méthicilline chez Staphylococcus aureus communautaire.

OBJECTIVE: The authors had for aim to assess the prevalence of community-acquired methicillin-resistant Staphylococcus aureus in France. METHOD: Two hundred fifty-four strains identified in 1,079 nasal samples from voluntary individuals were analyzed in 2002. An antibiogram (especially measuring the inhibition diameter of cefoxitine) and screening by oxacillin (6 mug/ml) allowed the identification of strains resistant to betalactams. The resistant phenotype was confirmed by amplification of the mecA gene by PCR. The distribution of strains was compared to the resistance to various antibiotics and especially to cotrimoxazole, macrolides, aminosides, and the mechanisms of resistance were determined. RESULTS: Eleven methicillin-resistant strains were detected in 254 carriers (4.33%), or 1% of the total population studied. CONCLUSION: Complementary tests (detection of the Panton-Valentine toxin, pulsed field electrophoresis) will be necessary to finish strain characterization. It can already be stated that compared to previous studies, community-acquired MRSA carriage is weak in France.

Rapid eye movement activity before spontaneous awakening in elderly subjects.

Previous research in young subjects found that rapid eye movement (REM) density is higher in those REM phases which are followed by an awakening (REM-W) than in those preceding NREM (REM-N), suggesting a 'gating role' of REM sleep toward the awakening. It is not yet known whether this evidence is maintained in elderly subjects, who display, relative to young subjects, more awakenings, different sleep states from which the awakenings come (NREM in a high proportion of cases) and a general impairment of rapid eye movement activity (REMA). To investigate this issue, we have compared in three different age groups (young, old and 'old old' subjects) the features of REMA, including REM density and the amount and duration of REM bursts, between REM-W and REM-N. Whereas in the young REM density is higher in REM-W than in REM-N, this difference is already reduced in the old group and fully cancelled in the old old subjects. The evidence that old individuals spontaneously wake up despite the absence of an increase of REMA could imply that in the aged awakening is not preceded by an increase of the arousal level (expressed in REM sleep by the REMA). The similar duration of REM bursts for REM-W and REM-N in both groups of old subjects suggests that with age a marked impairment occurs in the organizational aspects of REMs, independently from the following state.

Preterm infants prefer to be awake at night.

Wakefulness distribution during a 24-h period was studied in ten low-risk preterm and near term infants through video-recording. The highest amount of wakefulness was found in the night-time period between 02:00 and 05:00 h. This result is different from what was observed in infants during the first year of life, and similar to what was found in the foetus.

Polygraphic investigation of 24-h waking distribution in infants.

An evening forbidden zone for sleep has been shown for adults. This research was aimed to ascertain the prevalence of waking in the evening in early development. Twelve infants, aged between 2 weeks and 11 months 3 weeks, were each recorded once over a 24-h period. Recordings included EEG, EOG, EMG, respiration, ECG, and behavioural observation. Four states were defined by combining behavioural and electrophysiological data. Wakefulness was defined by the presence of eyes open, eye movements and additionally body movements, and irregular respiration. In infants younger than 12 months and a half, a greater amount of wakefulness was observed in the time interval between 17 and 20. Older infants show uniform high amount of wakefulness during daytime. Our data corroborate the hypothesis that evening hours are those most frequently characterised by the behavioural waking state, suggesting that a forbidden zone for sleep exists in development and that its time placement corresponds to the one observed in the adult.

The organization of rapid eye movement activity during rapid eye movement sleep is further impaired in very old human subjects.

Rapid eye movement activity (REMA) during rapid eye movement (REM) sleep was studied in seven very old ('old-old') subjects. Beyond global quantitative features (REMA density), we evaluated the organizational aspects of REMA, that is its occurrence in burst mode, which were compared to a group of younger elderly subjects ('young-old'). REMA density in 'old-old' subjects is not significantly different from that of 'young-old' subjects. The same lack of difference in the two groups is found for the number of REMA bursts. By contrast, the duration of REMA bursts is reduced in the 'old-old' subjects, as well as the 'burst state-to-burst-state' probability, i.e. the probability for successive inter-REMA time intervals to be part of the same REMA burst. Our results clearly show that the trend towards an impairment of REMA organizational aspects continues with aging. This is consistent with the hypothesis that sleep disorganization keeps worsening with age. However, it is of interest to observe that the capability of producing REMA bursts is preserved despite aging.

Morning recall of verbal material depends on prior sleep organization.

Despite the evidence that sleep may facilitate memory, controversial findings concern the role of sleep states (NREM, REM). We put forward the hypothesis that sleep organization, i.e. the regular occurrence of NREM-REM cycles, more than sleep states per se, may be crucial for the retention of verbal material presented before sleep. An experiment was performed in which recall of verbal material was requested of young subjects after three different kinds of night sleep: undisturbed sleep, fragmented sleep without sleep cycles disorganization, and fragmented sleep interrupted with sleep disorganization. Morning recall of verbal material was impaired after the night with disturbed sleep cycles, whereas it was not after the night with preserved sleep cycles; the amount of REM was similar in both cases. We conclude that the recall of verbal material is greatly affected by sleep cycle disorganization.

Sleep organization in the first year of life: developmental trends in the quiet sleep-paradoxical sleep cycle.

The night sleep of 48 healthy drug-free infants, aged 1-54 weeks, was recorded and analysed in order to show how cycles contribute to sleep episode organization and how the balance among different sleep states (i.e. quiet sleep, paradoxical sleep and ambiguous sleep) within cycles changes as a function of age. A greater proportion of time spent in cycles (TCT) on total sleep time (TST), as a result of the lengthening of sleep cycles, was found in older infants, whereas sleep out of cycles decreases with age. The internal structure of the sleep cycles also changes with age, because of the increase in the proportion of quiet sleep (QS), the appearance of slow wave sleep (SWS) from the 21st week onwards, and the decrease in ambiguous sleep. The proportion of paradoxical sleep (PS), however, remains stable throughout the first year of age. The improvement of sleep organization across the first year of life is paralleled by an internal restructuring of the cycle, involving mainly changes in QS. We may speculate that both changes, one involving the lengthening of cycle and the other involving the increase in QS component, contribute to the improvement of biological and psychological sleep functions during development.

Diurnal variation in spontaneous eye-blink rate.

The daily pattern of spontaneous eye-blink rate (BR), a non-invasive peripheral measure of central dopamine activity, was investigated in 24 healthy subjects. The spontaneous eye-blink rate showed a stable pattern in morning, midday and afternoon hours. A significant increase was found at the evening time point (20.30 h). The finding is suggestive of a late evening increase of central dopamine activity. An increased level of subjective sleepiness was also found at the same evening point, at a time corresponding to the 'evening wake maintenance zone' or the 'forbidden zone for sleep'. A possible hypothesis is that the 'forbidden zone for sleep' may reflect a dopamine-mediated activation that counteracts a rising sleep drive. The role of diurnal variation of dopamine function should be considered both in the choice of the drug treatment regimen, and in the evaluation of biological and neuropsychological parameters.

The organization of rapid eye movement activity during rapid eye movement sleep is impaired in the elderly.

Rapid eye movement activity (REMA) during rapid eye movement activity (REM) sleep was studied in eight elderly subjects and six young adults as a control group. Beyond global quantitative features (REMA density), we evaluated the organizational aspects of REMA, that is its occurrence in burst mode, still largely unknown in the aged. REMA density in the elderly is not significantly different than that of young adults. By contrast, the duration of REMA bursts is reduced in the elderly, as well as the 'burst state-to-burst-state' probability, i.e. the probability for successive inter-REMA time intervals to be part of the same REMA burst. These results show that global aspects of the quantitative features of REMA are preserved in the elderly, whereas their organizational aspects are impaired. These data are consistent with the hypothesis that aging is associated with a difficulty in maintaining physiological processes over time.

Spontaneous awakenings from sleep in the first year of life.

Spontaneous awakenings from nocturnal sleep were studied in a sample of 48 healthy infants (M = 26, F = 22), in four age groups (1 to 7 weeks, 8 to 15 weeks, 17 to 22 weeks, 25 to 54 weeks). Consistent with previous data, the number of awakenings is reported less frequently at later ages, owing to a lower frequency of awakenings out of REM sleep. Like young adults, infants in all age groups awake more often from REM than from quiet sleep (QS); this is particularly evident in the first 6 months of life, less so in the second. The duration of the bouts of wakefulness following awakenings remains stable with age. Awakenings out of QS are followed by longer periods of wakefulness than those out of REM sleep, although in older infants the duration is considerably reduced. Night sleep first shows a decrease in the number of awakenings out of REM sleep and then continues after the sixth month of life with the shortening of the wakefulness after awakenings out of QS. In the two younger groups, the distribution of the awakenings shows two main peaks and one main peak differently located during the night; a polymodal pattern appears in group 3, and is even more evident in group 4. It should be stressed that several changes as a function of age occur in the second 6 months of life, indicating this as a period of intense developmental change in sleep-wake rhythms.

A 50-Hz electromagnetic field impairs sleep.

In view of reports of health problems induced by low frequency (50-60 Hz) electromagnetic fields (EMF), we carried out a study in 18 healthy subjects, comparing sleep with and without exposure to a 50 Hz/1 mu Tesla electrical field. We found that the EMF condition was associated with reduced: total sleep time (TST), sleep efficiency, stages 3 + 4 slow wave sleep (SWS), and slow wave activity (SWA). Circulating melatonin, growth hormone, prolactin, testosterone or cortisol were not affected. The results suggest that commonly occurring low frequency electromagnetic fields may interfere with sleep.

Alertness-enhancing drugs as a countermeasure to fatigue in irregular work hours.

Irregular work/rest patterns frequently cause disturbed sleep and excessive sleepiness and accidents. This review is focused on four pharmacological countermeasures-the "new" drugs modafinil and pemoline, the traditional caffeine, and, as a reference, amphetamine. It is concluded that there is still too little data available to decide whether systematic use of alertness-enhancing drugs is feasible in occupational settings. D-Amphetamine is ruled out because of its abuse potential and mood effects. Modafinil and pemoline have not been tested in field situations, whereas caffeine certainly is used to improve alertness during work, but the use is spontaneous/ad hoc, and there is still a lack of data on its systematic application. Particularly, the optimal amount and pattern of administration need elucidation.

Seasonality of mood in Italy: role of latitude and sociocultural factors.

A mail survey of degree of seasonal suffering was conducted in Italy using the SPAQ (Seasonal Pattern Assessment Questionnaire). Experiencing seasonal changes as a problem was reported by more than half of the 543 responders. Both mean GSS (Global Seasonality Score) and circannual profile of 'feeling worst' yielded results similar to those reported in the USA at comparable latitudes. Global prevalences of SAD, Reverse-SAD and Sub-SAD were 4.4, 2.1 and 4.8%, respectively. Female sex and young age were associated with a higher degree of seasonal sensitivity. No clear evidence was found of higher sensitivity at higher latitudes or of a significant influence of sociocultural factors.