The impact of sleep deprivation on product quality and procedure effectiveness in a laparoscopic physical simulator: a randomized controlled trial

BACKGROUND

To compare the impact of sleep deprivation after 24-hour duty (post-call) with that of 8-hour work (post-work) on product quality (PQ) and procedure effectiveness (PE) in a laparoscopic physical simulator.

METHODS

Voluntary surgeons and nurses were pretested with the Epworth Sleepiness Scale (ESS) and Minimally Invasive Surgical Trainer-Virtual Reality (MIST-VR). Surgical task was suturing perforated ulcer on a foam stomach in a physical simulator. PQ and PE were measured by accuracy error (AE), tissue damage (TD) leak rate (LR), goal- (GDA) non-goal-directed actions (NGDA), and operating time (OT), respectively. Construct validity was assessed comparing measures when surgeons and nurses performed the surgical task. Inter-rater reliability (IRR) was assessed by Kendall's tau b coefficient. An 80% power parallel block randomization design at alpha = .05 required 60 subjects.

RESULTS

Thirty-two post-call surgeons and 32 post-work surgeons were well matched for age, gender, practice duration, and ESS and MIST-VR scores. The amount of time slept in the previous 24 hours was 1.5 versus 6.5 hours (P < .05). AE (1.0 mm vs. .5 mm), TD (2.18 mm vs. 2.18 mm), LR (56.2% vs. 65.6%), GDA (33.5 vs. 32.5), NGDA (.56 vs. .31), and OT (381.0 seconds vs. 364.5 seconds) were not significantly different when 32 surgeons in the post-call arm were compared with their 32 counterparts in the post-work arm, respectively. Construct validity was shown by significant improvement in 4 outcome measures (AE 1.0 mm vs. 2.0 mm, P = .00001; GDA 32.5 vs. 39.0, P = .07, NGDA .43 vs. .96, P = .045; and OT 377.5 vs. 557.0, P = .0005) when 64 surgeons performed the task as compared to 64 nurses. Tau b for IRR was 1.0 (P < .0001) for AE, TD, LR, and OT, .75 (P = .325) for GDA, and .77 (P = .305) for NGDA.

CONCLUSIONS

Sleep deprivation had no impact on the studied outcome measures of a surgical task performed in a laparoscopic simulator.

Neuroimaging and sleep medicine

In sleep medicine, patients with sleep disorders are evaluated and treated. The primary assessment tool of the field has traditionally been polysomnography. While polysomnography has been helpful in the evaluation of some sleep disorders, such as sleep apnea syndrome and periodic limb movement disorder, it has been less helpful in others, such as the insomnias, or sleep disorders secondary to mental disorders. These disorders are presumed to stem from some alteration in brain function that disrupts sleep. The development of functional neuroimaging methods provides a means to understand brain function in patients with sleep disorders in a manner not accessible to polysomnography. This paper summarizes functional neuroimaging findings during healthy sleep, then, reviews available studies in sleep disorders patients, and studies addressing the pharmacology of sleep and sleep disorders. Areas in which functional neuroimaging methods may be helpful in sleep medicine, and in which future development is advised, include: (1) clarification of pathophysiology; (2) aid in differential diagnosis; (3) assessment of treatment response; (4) guiding new drug development; and (5) monitoring treatment response.

An electroencephalographic fingerprint of human sleep

Homeostatic and circadian processes are basic mechanisms of human sleep which challenge the common knowledge of large individual variations in sleep need or differences in circadian types. However, since sleep research has mostly focused on group measures, an approach which emphasizes the similarities between subjects, the biological foundations of the individual differences in normal sleep are still poorly understood. In the present work, we assessed individual differences in a range of EEG frequencies including sigma activity during non-REM sleep (8.0-15.5 Hz range) in a group of 10 subjects who had participated in a slow-wave sleep (SWS) deprivation study. We showed that, like a "fingerprint", a particular topographic distribution of the electroencephalogram (EEG) power along the antero-posterior cortical axis distinguishes each individual during non-REM sleep. This individual EEG-trait is substantially invariant across six consecutive nights characterized by large experimentally induced changes of sleep architecture. One possible hypothesis is that these EEG invariances can be related to individual differences in genetically determined functional brain anatomy, rather than to sleep-dependent mechanisms.

It's Practice, with Sleep, that Makes Perfect: Implications of Sleep-Dependent Learning and Plasticity for Skill Performance

Although there is no consensus regarding the functions of sleep, one exciting hypothesis is that sleep contributes importantly to learning and memory. Over the last decade, several studies have provided substantive evidence supporting the role of sleep in memory processing. This article focuses on sleep-dependent learning and brain plasticity in humans, specifically in the development of skill performance that is the foundation of many sports actions. The different forms and stages of human memory are discussed, then evidence of sleep-dependent skill learning and associated sleep-dependent brain plasticity is described. In conclusion, a consideration of the fundamental importance of sleep in real-life skill learning is provided.

Validation of Impact of Events Scale in nurses under threat of contagion by severe acute respiratory syndrome

The purpose of the present study was to validate the Impact of Events Scale (IES) in a sample of nurses working under threat of severe acute respiratory syndrome (SARS). The internal consistency, construct validity and convergent validity of the instrument were examined in a sample of 128 nurses during the SARS outbreak in Taiwan. Principal component analysis followed by a quartimax rotation were used to derive a two-factor solution, labeled intrusion (factor 1) and avoidance (factor 2), with both factors accounting for 50.7% of the explained variance. The total Cronbach's alpha of 0.90 reflected the good internal consistency of the instrument. Correlation with the Symptoms Checklist 90-R demonstrated the convergent validity of the IES. In conclusion, the IES can be used as a convenient, reliable and valid instrument for evaluation of the psychological distress of nurses working with the highly contagious disease.

Callosal agenesis affects consistency of laterality in a paw preference task in BALB/cCF mice

We tested the hypothesis that the ontogenetic development of the corpus callosum (CC) affects the consistency of laterality in a paw preference task. Adult male mice (55 normal and 29 acallosal) of the BALB/cCF strain were initially tested (twice; inter-test interval: 72 h) in an unbiased setup in which both forepaws could easily perform a reaching movement. In a subsequent test, animals were placed in a biased setup that favored the use of the non-preferred paw. Acallosal and normal mice were strongly lateralized in the unbiased setup. Additionally, while normal mice did not present a populational bias favoring one of the paws, acallosal mice presented a significant bias favoring the left paw. In the biased setup, left- and right-pawed normal mice were equally consistent (approximately 65% of the animals, in both groups, used the preferred paw of the initial two tests, in spite of the bias). Conversely, while left-pawed acallosal mice were as consistent (65%) as normal mice, only 20% of right-pawed mice were consistent. These results suggest that the development of the CC affects consistency of laterality in a side-dependent manner. These results are discussed considering the role of the CC in the establishment of behavioral lateralization.

The influence of white noise on sleep in subjects exposed to ICU noise

BACKGROUND AND PURPOSE

There is disagreement in the literature about the importance of sleep disruption from intensive care unit (ICU) environmental noise. Previous reports have assumed that sleep disruption is produced by high-peak noise. This study aimed to determine whether peak noise or the change in noise level from baseline is more important in inducing sleep disruption. We hypothesized that white noise added to the environment would reduce arousals by reducing the magnitude of changing noise levels.

PATIENTS AND METHODS

Four subjects underwent polysomnography under three conditions: (1) baseline, (2) exposure to recorded ICU noise and (3) exposure to ICU noise and mixed-frequency white noise, while one additional subject completed the first two conditions. Baseline and peak noise levels were recorded for each arousal from sleep.

RESULTS

A total of 1178 arousals were recorded during these studies. Compared to the baseline night (13.3+/-1.8 arousals/h) the arousal index increased during the noise (48.4+/-7.6) but not the white noise/ICU noise night (15.7+/-4.5) (P<0.004). The change in sound from baseline to peak, rather than the peak sound level, determined whether an arousal occurred and was the same for the ICU noise and white noise/ICU noise condition (17.7+/-0.4 versus 17.5+/-0.3 DB, P=0.65).

CONCLUSIONS

Peak noise was not the main determinant of sleep disruption from ICU noise. Mixed frequency white noise increases arousal thresholds in normal individuals exposed to recorded ICU noise by reducing the difference between background noise and peak noise.

Quantitative assessment of five behavioural laterality measures: distributions of scores and intercorrelations among right-handers

Five behavioural laterality measures (degree of right-handedness, ear dominance, ocular dominance, line bisection performance, and lateral preference as assessed by preferred direction of conjugate lateral eye movements) were analysed in 1171 right-handers by merging data from 15 different samples. All laterality aspects were assessed quantitatively by using well controlled performance measures instead of questionnaires. The distributions and intercorrelations of the measures as well as their test-retest reliabilities were examined. Results show moderately high reliabilities for all measures, and clearly demonstrate considerable variability among dextrals in the direction and magnitude of the obtained behavioural laterality measures. Most importantly, independence of the different measures questions some common assumptions in laterality research. It seems unlikely, for instance, that handedness and other aspects of laterality may be a product of one single underlying mechanism of brain lateralisation.

Electroencephalographic Changes during Respiratory Cycles Predict Sleepiness in Sleep Apnea

Common polysomnographic measures of sleep-disordered breathing have shown a disappointing ability to predict important consequences such as excessive daytime sleepiness. Using novel analytic techniques, this study tested the hypothesis that numerous, brief disruptions in cortical activity could occur on a breath-to-breath basis during nonapneic sleep. Spectral analysis proved the existence of respiratory cycle-related electroencephalographic changes in each of 38 adult patients evaluated by polysomnography for sleep-disordered breathing. Furthermore, the tendency for sigma (13-15 Hz) electroencephalographic power to vary with the respiratory cycle predicted next-day sleepiness as measured by the multiple sleep latency test. The predictive value was enhanced when the analysis was limited to those 27 patients who had sleep-disordered breathing (more than 5 apneas or hypopneas per hour of sleep). In contrast, nocturnal rates of apneas and hypopneas, as well as minimal oxygen saturation, did not predict sleepiness as well. On average, sigma power increased notably during inspiration, whereas delta (1-4 Hz) power showed a simultaneous decrease. We conclude that electroencephalographic activity shows detectable changes during nonapneic respiratory cycles in adults evaluated for sleep-disordered breathing. Quantification of these changes, which may reflect numerous inspiratory microarousals, could prove useful in prediction of excessive daytime sleepiness.

Total sleep deprivation and novelty processing: implications for frontal lobe functioning

OBJECTIVE

Mounting evidence suggests that the frontal lobes are particularly vulnerable to total sleep deprivation (TSD). Detection of novelty involves the frontal lobes. The presentation of rare, novel stimuli elicits an event-related potential (novel P3), which maximizes over anterior regions of the scalp. We hypothesized that TSD would impair novelty detection, resulting in a smaller novel P3 over the frontal region, with a topographic shift toward posterior areas.

METHODS

An auditory novelty oddball task was administered to a TSD group after 36 h of waking and again following recovery sleep, and to a control group after 12 h of waking. EEG was recorded from Fz, Cz and Pz.

RESULTS

A large anterior P3 was elicited in the control group. In the TSD group, this novel P3 was smaller at Fz. A later novel positivity appeared in parietal areas. The novel P3 returned to baseline levels and the late novel P3 was difficult to observe following recovery sleep.

CONCLUSIONS

TSD appears to compromise the usual automatic detection of novelty probably due to frontal deactivation. Participants may compensate by relying on posterior brain mechanisms involving active memory comparison. The late novel P3 component may also reflect a secondary effortful attempt to encode and to categorize novel stimuli.

SIGNIFICANCE

This study suggests that TSD may compromise cognitive functioning in different regions of the brain. The detection of novelty, probably mediated by the frontal lobes, is particularly at risk.

Toward an integrative theory of sleep and dreaming

Non-rapid-eye-movement sleep (NREMS) is triggered by the accumulation of adenosine, as a result of the perceptual overload of the brain cortex. NREMS starts in the most burdened regions of the cortex first and then eventually, after the released adenosine has reached the ventrolateral pre-optic nucleus area of the hypothalamus, triggers the "general NREMS pattern". This is accompanied by the usual familiar changes in the thalamocortical system. When NREMS reaches the slow-wave sleep (SWS) phase, with its predominant delta activity, brain metabolism drops significantly with the brain temperature, and this is recognized by the alarm system in the pre-optic anterior hypothalamus and/or the other thermostat circuit in the brainstem as a life-threatening situation. This alarm system triggers a reaction similar to abortive or partial awakening called rapid-eye-movement sleep (REMS), which is aimed at restoring the optimal body-core temperature. As soon as this restoration is accomplished by the activation of the brainstem-to-cortex ascending pathways, NREMS may continue, as may the interchange of the two sleep phases during the entire sleep period. During both NREMS and REMS, the same essential pattern occurs in the cortex: the loops "used" during the previous waking period, now deprived of external input, replay their waking activity at a lower frequency, one which enables them to restore the membrane's potential (possibly by means of LTD). During REMS, however, the cholinergic flood originating in the LTD/PPT nuclei of the pons tegmentum, increases in the basal forebrain and, provoking theta activity in the medial septum is extended to the hippocampus, causing the circuits that are active at that particular moment in the cortex, to store the information they carry as memory. This is the explanation of both the memory improvement known to be related to REMS and of dreams. Both phenomena are clearly side effects of REMS.

Human parahippocampal activity: non-REM and REM elements in wake–sleep transition

The covert-rapid-eye-movement (REM) sleep hypothesis of dreaming suggests that elements of REM sleep emerge during sleep onset, leading to vivid hypnagogic imagery. Based on parahippocampal electrocorticography of epileptic patients we found an increase in REM-like 1.5-3.0 Hz parahippocampal activity during wake-sleep transition, which peaks after on average 30s of sleep onset, and reaches 82% of REM sleep value. The increase in 1.5-3.0 Hz parahippocampal activity followed alpha dropout, but did not relate to short-term fluctuations in alpha waves or sleep spindles. Non-REM sleep-specific slow (<1.25 Hz) activity showed a continuous increase during wake-sleep transition in both temporal scalp and parahippocampal recordings. It is suggested that REM-like parahippocampal rhythmic slow activity is an after-effect of hypothalamic wake-promoting centers' switch-off at sleep onset, leading to an inhibited hippocampal functioning and hypnagogic hallucinations.

Nurses are overtired and not getting enough sleep

Nursing has always been a tiring and demanding occupation. More recently, there have been complaints by nurses that the situation is getting worse. For example, one ward sister of 30 years' experience told me that ‘no-one seems to care about how we feel anymore; all senior management are interested in is bed vacancies and when patients will be ready for discharge’. She went on to describe a typical day on her ward, pointing out how tired the nurses were and how impossible it was to give the holistic nursing care that patients required.

Are difficulties perceiving and expressing emotions associated with low-back pain? The relationship between lack of emotional awareness (alexithymia) and 12-month prevalence of low-back pain in 1180 urban public transit operators

OBJECTIVE

To assess the association of alexithymia (deficit in emotional awareness) with 12-month prevalence of low back pain (LBP) cross-sectionally in a cohort study of 1180 San Francisco transit operators.

METHODS

Alexithymia was measured by the Toronto Alexithymia Scale (TAS-20). LBP was assessed in medical histories during drivers relicensing exams. Multivariate logistic regression analyses controlled for demographic, behavioral (smoking, alcohol, coping style), and physical and psychosocial job factors measured by questionnaire and interview.

RESULTS

Of all the drivers, 31.4% suffered from LBP. Scoring in the upper quartile of alexithymia summary scores was associated with twofold higher odds of LBP (adjusted odds ratio=2.00, 95% confidence interval: 1.31-3.00). The association was stronger in women (adj. OR=4.35) than in men (adj. OR=1.83). The factor "difficulty identifying feelings" showed the strongest association with LBP (adj. OR=2.23).

CONCLUSION

The results support an association between alexithymia and LBP.

Sleep deprivation, cognitive performance, and hormone therapy in postmenopausal women

OBJECTIVE

To study the effects of sleep deprivation on cognitive performance in postmenopausal women and to evaluate whether hormone therapy (HT) has a modifying effect on coping.

DESIGN

Twenty-six postmenopausal women, aged 58 to 72 years (mean 64 years), volunteered for the study (HT users, n = 16; nonusers, n = 10). They spent four consecutive nights in the sleep laboratory. The cognitive tests were performed three times: after the baseline night, after one night of sleep deprivation, and after the rebound night. The cognitive measures included visual episodic memory, visuomotor performance, verbal attention, and shared attention.

RESULTS

The practice effect typically occurring in cognitive tests was blunted during sleep deprivation, which indicated deterioration of performance. At rebound, performance improved in visual episodic memory (immediate recall P < 0.01; delayed recall P < 0.05), visuomotor performance (P < 0.001), verbal attention (P < 0.0001), and shared attention (P < 0.05). HT users performed better than nonusers in the visual episodic memory test (P < 0.05) and in one of three subtests of shared attention (cancellation P = 0.040). Otherwise hormone therapy did not influence the results.

CONCLUSIONS

In postmenopausal women, sleep deprivation impaired visual functions and attention. However, this effect was not prolonged because after one rebound night the performance was improved, compared with baseline. Hormone therapy did not modify the cognitive performance during sleep deprivation.

Neurobehavioural effects of electromagnetic fields

Very few laboratory studies in children have explored the effects of exposure to low level electromagnetic fields (EMFs) on neurobehavioural function. Studies investigating effect on neurotransmitters, cognitive function and brain activity in adults and animals indicate that acute exposure to EMFs does not appear to engender any consistent physiological or behavioural impairment although a few subtle effects may occur. This suggests that exposure of children to low level EMFs may not cause significant detrimental effects on brain function. However the available evidence is not sufficient to draw any definite conclusions, and further laboratory studies are required. In particular, experiments investigating the effects of radiofrequency (RF) fields on the performance of well-characterised cognitive and behavioural tasks by immature and developing animals are recommended, if studies with children cannot be performed for ethical and practical reasons.

Personality, coping and sperm count

Previous research has suggested an association between personality traits and coping, as well as between coping and sperm concentration. In the present study, both domains of research were combined, leading to the formulation of specific hypotheses. A total of 54 healthy volunteers were given questionnaires twice to assess personality traits and coping behaviour. Participants also produced up to three semen specimens. As hypothesized, active coping was correlated negatively with neuroticism (r = -0.59) and positively with conscientiousness (r = 0.56), whereas sperm concentration was correlated negatively with both active coping (r = -0.28) and conscientiousness (r = -0.37). The relationship between conscientiousness and sperm concentration did not appear to be mediated by active coping. Although the correlations were small, evidence is mounting that psychological aspects and male sperm parameters are not independent. The present findings, however, should not lead to the conclusion that conscientiousness and active forms of coping are characteristics of infertile patients.

Decrease of functional coupling between left and right auditory cortices during dichotic listening: An electroencephalography study

The present study focused on functional coupling between human bilateral auditory cortices and on possible influence of right over left auditory cortex during dichotic listening of complex non-verbal tones having near (competing) compared with distant non-competing fundamental frequencies. It was hypothesized that dichotic stimulation with competing tones would induce a decline of functional coupling between the two auditory cortices, as revealed by a decrease of electroencephalography coherence and an increase of directed transfer function from right (specialized for the present stimulus material) to left auditory cortex. Electroencephalograph was recorded from T3 and T4 scalp sites, overlying respectively left and right auditory cortices, and from Cz scalp site (vertex) for control purposes. Event-related coherence between T3 and T4 scalp sites was significantly lower for all electroencephalography bands of interest during dichotic listening of competing than non-competing tone pairs. This was a specific effect, since event-related coherence did not differ in a monotic control condition. Furthermore, event-related coherence between T3 and Cz and between T4 and Cz scalp sites showed no significant effects. Conversely, the directed transfer function results showed negligible influence at group level of right over left auditory cortex during dichotic listening. These results suggest a decrease of functional coupling between bilateral auditory cortices during competing dichotic stimuli as a possible neural substrate for the lateralization of auditory stimuli during dichotic listening.

Genes for normal sleep and sleep disorders

Sleep and wakefulness are complex behaviors that are influenced by many genetic and environmental factors, which are beginning to be discovered. The contribution of genetic components to sleep disorders is also increasingly recognized as important. Point mutations in the prion protein, period 2, and the prepro-hypocretin/orexin gene have been found as the cause of a few sleep disorders but the possibility that other gene defects may contribute to the pathophysiology of major sleep disorders is worth in-depth investigations. However, single gene disorders are rare and most common disorders are complex in terms of their genetic susceptibility, environmental effects, gene-gene, and gene-environment interactions. We review here the current progress in the genetics of normal and pathological sleep.

Sleep deprivation in junior doctors--house officers in Singapore

House officers are known to endure marked levels of sleep deprivation in administration of their duties. We aim to establish sleep patterns of local house officers while on the job and the impact it might have on their mood and sleepiness state. We also studied their sleep during their final year of medical school and pre-university for identification of any prior sleep deprivation. Questionnaires were used to assess sleep and mood change. Sleepiness levels on the day after call were assessed using the Stamford Sleepiness Scale. Subjects were found to sleep a median of only 1.0 (+/- 2.0) h per night on call and 6.0 h (+/- 1.0) per non-call night. They suffered median of 5 interruptions (+/- 5) during sleep on one night call. Night call was found to adversely affect mood in 89.5% of the subjects while daytime sleepiness levels following call were found to increase the more the time spent at work after call. Subjects were found to have had 6.5 h (+/- 1.0) of sleep per night during final year of medical school and 8.0 h (+/- 1.0) in final year of pre-university. House officers enter the profession chronically sleep-deprived. The call schedule and general work regime further add to the existent sleep deprivation and may have adverse consequences on patient care and doctor's health. This calls for measures to be instituted for provision of proper sleep and work hours for them.

Right hemisphere specialization for intensity discrimination of musical and speech sounds

Sound intensity is the primary and most elementary feature of auditory signals. Its discrimination plays a fundamental role in different behaviours related to auditory perception such as sound source localization, motion detection, and recognition of speech sounds. This study was aimed at investigating hemispheric asymmetries for processing intensity of complex tones and consonant-vowel syllables. Forty-four right-handed non-musicians were presented with two dichotic matching-to-sample tests with focused attention: one with complex tones of different intensities (musical test) and the other with consonant-vowel syllables of different intensities (speech test). Intensity differences (60, 70, and 80 dBA) were obtained by altering the gain of a synthesized harmonic tone (260 Hz fundamental frequency) and of a consonant-vowel syllable (/ba/) recorded from a natural voice. Dependent variables were accuracy and reaction time. Results showed a significant clear-cut left ear advantage in both tests for both dependent variables. A monaural control experiment ruled out possible attentional biases. This study provides behavioural evidence of a right hemisphere specialization for the perception of the intensity of musical and speech sounds in healthy subjects.

Lateralization of pupillary light reflex parameters

OBJECTIVE

The aim of this study was to determine differing reactions of the left and right eyes with regard to pupillary light reflex (PLR) parameters.

METHODS

All together 90 healthy subjects were included. In the first test series, 34 subjects were investigated on both eyes (left eye was tested first, three tests per day and one reliability test). In the second test series, 32 subjects were studied while changing the beginning side. In the last test series, 29 subjects were investigated 12 times each within 1h (beginning side changed, without spoken advice). Infrared pupillometry was used to study pupil diameter, latency time, relative amplitude, contraction/dilation velocity, and pupil redilation time.

RESULTS

The study demonstrated significant differences of PLR parameters between both eyes. In contrast to the pupil diameter of the left eye the parasympathetically-dominated right eye was not influenced by vocal instructions or by changing the beginning side.

CONCLUSIONS

PLR parameters might indicate functional lateralization of autonomic function in the central nervous system. High sensitivity of the procedure (arousal due to spoken advice, time of day) is advantageous for various psychophysiological investigations.

SIGNIFICANCE

Differences between both eyes might point towards cortical lateralization of central autonomic function.

State transitions between wake and sleep, and within the ultradian cycle, with focus on the link to neuronal activity

The structure of sleep across the night as expressed by the hypnogram, is characterised by repeated transitions between the different states of vigilance: wake, light and deep non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep. This review is concerned with current knowledge on these state transitions, focusing primarily on those findings that allow the integration of data at cellular level with spectral time-course data at the encephalographic (EEG) level. At the cellular level it has been proposed that, under the influence of circadian and homeostatic factors, transitions between wake and sleep may be determined by mutually inhibitory interaction between sleep-active neurons in the hypothalamic preoptic area and wake-active neurons in multiple arousal centres. These two fundamentally different behavioural states are separated by the sleep onset and the sleep inertia periods each characterised by gradual changes in which neither true wake nor true sleep patterns are present. The results of sequential spectral analysis of EEG data on moves towards and away from deep sleep are related to findings at the cellular level on the generating mechanisms giving rise to the various NREM oscillatory modes under the neuromodulatory control of brainstem-thalamic activating systems. And there is substantial evidence at cellular level that transition to and from REM sleep is governed by the reciprocal interaction between cholinergic REM-on neurons and aminergic REM-off neurons located in the brainstem. Similarity between the time-course of the REM-on neuronal activity and that of EEG power in the high beta range (approximately 18-30 Hz) allows a tentative parallelism to be drawn between the two. This review emphasises the importance of the thalamically projecting brainstem activating systems in the orchestration of the transitions that give rise to state progression across the sleep-wake cycle.

Beta2-containing nicotinic receptors contribute to the organization of sleep and regulate putative micro-arousals in mice

The cholinergic system is involved in arousal and in rapid eye movement sleep (REMS). To evaluate the contribution of nicotinic acetylcholine receptors (nAChRs) to these functions, we studied with polygraphic recordings the regulation of sleep in mice lacking the beta2 subunit gene of the nAChRs, a major component of high-affinity nicotine binding sites in the brain. Nicotine (1-2 mg/kg, i.p.) increased wakefulness in wild-type but not knock-out animals, indicating that beta2-containing nAChRs mediate the arousing properties of nicotine. Under normal conditions, the beta2-/- mice displayed the same amounts of waking, non-REM sleep (NREMS) and REMS as their wild-type counterparts. However, they exhibited longer REMS episodes and a reduced fragmentation of NREMS by events characterized notably by a transient drop in EEG power and frequently associated with EMG activation, tentatively referred to as micro-arousals. Respiration monitoring showed that these events were accompanied with, but not caused by, breathing irregularities. Sleep deprivation of beta2-/- mice resulted in a normal increase in REMS episode duration and NREMS delta power but yielded a reduction of the number of micro-arousals in NREMS. In contrast, in beta2-/- mice, a 1 hr immobilization stress failed to produce the normal rebound in REMS in the following 12 hr and, instead, was associated with increased NREMS fragmentation and sustained corticosterone levels. Our results show that the beta2-containing nAChRs contribute to the organization of sleep by regulating the transient phasic activity in NREMS, the REMS onset and duration, and the REMS-promoting effect of stress.

Inter-rater reliability of sleep cyclic alternating pattern (CAP) scoring and validation of a new computer-assisted CAP scoring method

OBJECTIVE

To assess inter-rater reliability between different scorers, from different qualified sleep research groups, in scoring visually the Cyclic Alternating Pattern (CAP), to evaluate the performances of a new tool for the computer-assisted detection of CAP, and to compare its output with the data from the different scorers.

METHODS

CAP was scored in 11 normal sleep recordings by four different raters, coming from three sleep laboratories. CAP was also scored in the same recordings by means of a new computer-assisted method, implemented in the Hypnolab 1.2 (SWS Soft, Italy) software. Data analysis was performed according to the following steps: (a) the inter-rater reliability of CAP parameters between the four different scorers was carried out by means of the Kendall W coefficient of concordance; (b) the analysis of the agreement between the results of the visual and computer-assisted analysis of CAP parameters was also carried out by means of the Kendall W coefficient; (c) a 'consensus' scoring was obtained, for each recording, from the four scorings provided by the different raters, based on the score of the majority of scorers; (d) the degree of agreement between each scorer and the consensus score and between the computer-assisted analysis and the consensus score was quantified by means of the Cohen's k coefficient; (e) the differences between the number of false positive and false negative detections obtained in the visual and in the computer-assisted analysis were also evaluated by means of the non-parametric Wilcoxon test.

RESULTS

The inter-rater reliability of CAP parameters quantified by the Kendall W coefficient of concordance between the four different scorers was high for all the parameters considered and showed values above 0.9 for total CAP time, CAP time in sleep stage 2 and percentage of A phases in sequence; also CAP rate showed a high value (0.829). The most important global parameters of CAP, including total CAP rate and CAP time, scored by the computer-assisted analysis showed a significant concordance with those obtained by the raters. The agreement between the computer-assisted analysis and the consensus scoring for the assignment of the CAP A phase subtype was not distinguishable from that expected from a human scorer. However, the computer-assisted analysis provided a number of false positives and false negatives significantly higher than that of the visual scoring of CAP.

CONCLUSIONS

CAP scoring shows good inter-rater reliability and might be compared in different laboratories the results of which might also be pooled together; however, caution should always be taken because of the variability which can be expected in the classical sleep staging. The computer-assisted detection of CAP can be used with some supervision and correction in large studies when only general parameters such as CAP rate are considered; more editing is necessary for the correct use of the other results.

SIGNIFICANCE

This article describes the first attempt in the literature to evaluate in a detailed way the inter-rater reliability in scoring CAP parameters of normal sleep and the performances of a human-supervised computerized automatic detection system.

Interoceptive sensitivity and self-reports of emotional experience

People differ in the extent to which they emphasize feelings of activation or deactivation in their verbal reports of experienced emotion, termed arousal focus (AF). Two multimethod studies indicate that AF is linked to heightened interoceptive sensitivity (as measured by performance on a heartbeat detection task). People who were more sensitive to their heartbeats emphasized feelings of activation and deactivation when reporting their experiences of emotion over time more than did those who were less sensitive. This relationship was not accounted for by several other variables, including simple language effects. Implications for the role of interoception in experienced emotion and the validity of self-reported emotion are discussed.

Mechanisms of arousal from sleep and their consequences

PURPOSE OF REVIEW

In recent years, understanding of the mechanisms by which sleep is maintained and the consequences of abnormal arousal from sleep has improved rapidly. This review describes the recent insights into the nature of sleep and arousal and the particular insights gained in common disease states such as sleep-disordered breathing.

RECENT FINDINGS

Expansion of the definitions of the classic stages of non-REM and REM sleep to include consideration of the role of cyclic alternating pattern sleep as a gating mechanism for arousal and maintenance of stable sleep has led to a significant advancement in understanding the nature of normal and pathologic arousals from sleep. In addition, the effect of arousals from sleep on cerebral cortical electrophysiology and autonomic activation has been further defined, with a potential effect on clinical practice.

SUMMARY

Arousal from sleep is dependent on wake-promoting influences overwhelming forces promoting sleep. Autonomic activation and cortical arousal can significantly affect and destabilize sleep homeostasis. The understanding of sleep-respiration interactions continues to evolve. The definition of the minimal arousal event is an important research goal. It will be important in clinical practice and research to consider sleep stability domains as a complement to sleep depth staging to allow better understanding of the relative stability and instability of the system and to consider all components of the consequences of arousal.

Natural rhythm: evidence for occult 40Hz gamma oscillation in resting motor cortex

Fast gamma oscillations, often at 40 Hz, have been demonstrated throughout the brain including the thalamus, auditory, visual and motor cortices. The function of gamma rhythms is elusive, but several authors have hypothesized that they contribute to the "binding" of diverse information into a single coherent percept, and to the synchronization of movement. In skeletal muscle a "Piper rhythm" around 40 Hz is commonly observed during maximal voluntary contraction, and has been shown to correlate with activity of similar frequency in a limited area of contralateral motor cortex. Gamma rhythms are detected primarily during complex cortical activity, and are seldom recorded at rest or coherently over wide areas. Here we use bihemispheric transcranial magnetic stimulation (TMS) to study time-dependent correlations between evoked motor potentials from non-homologous muscles in opposite limbs of normal volunteers. The results suggest the presence of an occult, synchronous 40 Hz rhythm across broad areas of resting motor cortex in both hemispheres.

Enhanced Motor Cortex Excitability During Ipsilateral Voluntary Hand Activation in Healthy Subjects and Stroke Patients

BACKGROUND AND PURPOSE

It is still a matter of debate whether the ipsilateral voluntary hand activation has a facilitatory or inhibitory effect on the nondominant or affected hemisphere. To give an answer to this question is of great importance for the rehabilitation of stroke patients, because they often use the unaffected hand for compensation.

METHODS

Ten healthy volunteers and 11 stroke patients were investigated using transcranial magnetic stimulation (TMS). TMS was applied to the dominant/unaffected hemisphere during performance of different tasks (simple index finger abduction, pinch grip, and power grip) at various force levels (5%, 10%, 50%, and 100% maximal voluntary contraction) with the ipsilateral hand. Peak-to-peak amplitudes of motor-evoked potentials were used as measure for motor cortex excitability.

RESULTS

Both simple and complex tasks led to a facilitation of the contralateral corticospinal system at all levels of applied force. Not only the facilitatory effect in general but also the slope of the relationship between force level and MEP amplitude were significantly lower in stroke patients indicating that both the general activation level of the impaired motor system and the bandwidth of possible activation levels are diminished.

CONCLUSIONS

Voluntary activation of the hand does not exert an inhibitory effect on the excitability of the ipsilateral hemisphere in healthy volunteers or in stroke patients.

The relationship between alexithymia, depression, and sleep complaints

The study assessed in normal subjects the hypothesis of a specific association between alexithymia and poor sleep quality, taking into consideration the contribution of depression. Five hundred fifty-four university students (480 F and 74 M) filled out the Italian version of the 20-item Toronto Alexithymia Scale (TAS-20), the Center for Epidemiologic Studies Depression Scale (CES-D), and the Pittsburgh Sleep Quality Index (PSQI). TAS-20 scores were significantly correlated with many measures of self-rated poor sleep quality and also strongly correlated with depression scores. Any association between alexithymia and sleep complaints disappears when the contribution of depression is partialled out by multiple regressions, and only the well-known relationship between depression and impairment of sleep quality is confirmed.

Likelihood ratios: A simple and flexible statistic for empirical psychologists

Empirical studies in psychology typically employ null hypothesis significance testing to draw statistical inferences. We propose that likelihood ratios are a more straightforward alternative to this approach. Likelihood ratios provide a measure of the fit of two competing models; the statistic represents a direct comparison of the relative likelihood of the data, given the best fit of the two models. Likelihood ratios offer an intuitive, easily interpretable statistic that allows the researcher great flexibility in framing empirical arguments. In support of this position, we report the results of a survey of empirical articles in psychology, in which the common uses of statistics by empirical psychologists is examined. From the results of this survey, we show that likelihood ratios are able to serve all the important statistical needs of researchers in empirical psychology in a format that is more straightforward and easier to interpret than traditional inferential statistics.

Interhemispheric interaction between human dorsal premotor and contralateral primary motor cortex

We used transcranial magnetic stimulation (TMS) in a paired pulse protocol to investigate interhemispheric interactions between the right dorsal premotor (dPM) and left primary motor cortex (M1) using interstimulus intervals of 4, 6, 8, 10, 12, 16 and 20 ms in ten healthy subjects. A conditioning stimulus over right dPM at an intensity of either 90 or 110% resting motor threshold (RMT) suppressed motor-evoked potentials (MEPs) evoked in the first dorsal interosseous (FDI) muscle by stimulation of left M1. Maximum effects occurred for interstimulus intervals (ISIs) of 8-10 ms. There was no effect if the conditioning stimulus was applied 2.5 cm lateral, anterior or medial to dPM. The effect differed from previously described M1 interhemispheric inhibition in that the threshold for the latter was greater than 90% RMT, whereas stimulation of the dPM at the same intensity led to significant inhibition. In addition, voluntary contraction of the left FDI (i.e. contralateral to the conditioning TMS) enhanced interhemispheric inhibition from right M1 but had no effect on the inhibition from right dPM. Finally, conditioning to right dPM at 90% RMT reduced short-interval intracortical inhibition (SICI; at ISI = 2 ms) in left M1 whilst there was no effect if the conditioning stimulus was applied to right M1. We conclude that conditioning TMS over dPM has effects that differ from the previous pattern of interhemispheric inhibition described between bilateral M1s. This may reflect the existence of commissural fibres between dPM and contralateral M1 that may play a role in bimanual coordination.

Spectral Power Time-courses of Human Sleep EEG Reveal a Striking Discontinuity at ∼18 Hz Marking the Division between NREM-specific and Wake/REM-specific Fast Frequency Activity

Spectral power time-courses over the ultradian cycle of the sleep electroencephalogram (EEG) provide a useful window for exploring the temporal correlation between cortical EEG and sub-cortical neuronal activities. Precision in the measurement of these time-courses is thus important, but it is hampered by lacunae in the definition of the frequency band limits that are in the main based on wake EEG conventions. A frequently seen discordance between the shape of the beta power time-course across the ultradian cycle and that reported for the sequential mean firing rate of brainstem-thalamic activating neurons invites a closer examination of these band limits, especially since the sleep EEG literature indicates in several studies an intriguing non-uniformity of time-course comportment across the traditional beta band frequencies. We ascribe this tentatively to the sharp reversal of slope we have seen at approximately 18 Hz in our data and that of others. Here, therefore, using data for the first four ultradian cycles from 18 healthy subjects, we apply several criteria based on changes in time-course comportment in order to examine this non-uniformity as we move in 1 Hz bins through the frequency range 14-30 Hz. The results confirm and describe in detail the striking discontinuity of shape at around 18 Hz, with only the upper range (18-30 Hz) displaying a time-course similar to that of the firing-rate changes measured in brainstem activating neurons and acknowledged to engender states of brain activation. Fast frequencies in the lower range (15-18 Hz), on the other hand, are shown to be specific to non-rapid-eye-movement sleep. Splitting the beta band at approximately 18 Hz therefore permits a significant improvement in EEG measurement and a more precise correlation with cellular activity.

Increased periodic arousal fluctuations during non-REM sleep are associated to superior memory

Sleep has been implicated in the plastic cerebral changes that underlie learning and memory. The scientific investigation of people with exceptional memory has been relatively neglected. We report the results of a polysomnographic investigation of an individual with superior memory performance. The sleep structure, in terms of sleep induction and maintenance, as well as non-REM and REM sleep percentages, were normal. The main finding was an increased number of periodic arousal fluctuations during non-REM sleep (measured as cyclic alternating pattern, CAP) during two consecutive nights (7-8 S.D. units above that observed in age-matched controls). Since CAP rate reflects the structural organization of non-REM sleep, this observation supports the hypothesis of a link between non-REM sleep and declarative memory performance.

Learning increases human electroencephalographic coherence during subsequent slow sleep oscillations

Learning is assumed to induce specific changes in neuronal activity during sleep that serve the consolidation of newly acquired memories. To specify such changes, we measured electroencephalographic (EEG) coherence during performance on a declarative learning task (word pair associations) and subsequent sleep. Compared with a nonlearning control condition, learning performance was accompanied with a strong increase in coherence in several EEG frequency bands. During subsequent non-rapid eye movement sleep, coherence only marginally increased in a global analysis of EEG recordings. However, a striking and robust increase in learning-dependent coherence was found when analyses were performed time-locked to the occurrence of slow oscillations (<1 Hz). Specifically, the surface-positive half-waves of the slow oscillation resulting from widespread cortical depolarization were associated with distinctly enhanced coherence after learning in the slow-oscillatory, delta, slow-spindle, and gamma bands. The findings identify the depolarizing phase of the slow oscillations in humans as a time period particularly relevant for a reprocessing of memories in sleep.

Sleep in young adults with Asperger syndrome

Asperger syndrome (AS) is a neurodevelopmental disorder belonging to autism spectrum disorders. Both children and adults with AS have subjective impairment in the initiation and continuity of sleep, and studies using objective assessment are sparse. Twenty young AS adults with frequent complaints of low sleep quality were compared to 10 age-, gender- and education-matched controls without sleep complaints using polysomnography and spectral power analysis of slow-wave sleep. AS subjects displayed a similar polysomnographic profile as compared with controls. In spectral power analysis, a statistically nonsignificant trend towards decreased relative delta power and increased theta power in slow-wave sleep was found in the AS group. It seems that nonorganic insomnia, due to anxiety inherent in AS, is responsible for the low sleep quality in these subjects.

Gender differences in sleep and sleep-disordered breathing

Sleep and sleep disorders are different in several important ways between men and women. Because of pregnancy and menopause, women experience changes in sleep that may present as clinical problems. In clinical populations, women are more likely to present with insomnia than are men, although their sleep may be better preserved. The presentation of sleep apnea in women is distinct from that of men and is less likely to include a "classic" history of witnessed ap-nea or heavy snoring. More likely it presents with nonspecific symptoms, such as fatigue or mood disturbance. There are little data on the effects of different treatments for OSA between men and women. OHS is a syndrome that may be as common in women as in men. The role of hormones in its pathophysiology is not well-defined.

Spatially uniform and nonuniform analyses of electroencephalographic dynamics,with application to the topography of the alpha rhythm

Corticothalamic dynamics are investigated using a model in which spatial nonuniformities are incorporated via the coupling of spatial eigenmodes. Comparison of spectra generated using the nonuniform analysis with those generated using a uniform one demonstrates that, for most frequencies, local activity is only weakly dependent on activity elsewhere in the cortex; however, dispersion of low-wave-number activity ensures that distant dynamics influence local dynamics at low frequencies (below approximately 2 Hz ), and at the alpha frequency (approximately 10 Hz ), where propagating signals are inherently weakly damped, and wavelengths are large. When certain model parameters have similar spatial profiles, as is expected from physiology, the low-frequency discrepancies tend to cancel, and the uniform analysis with local parameter values is an adequate approximation to the full nonuniform one across the whole spectrum, at least for large-scale nonuniformities. After comparing the uniform and nonuniform analyses, we consider one possible application of the nonuniform analysis: studying the phenomenon of occipital alpha dominance, whereby the alpha frequency and power are greater at the back of the head (occipitally) than at the front. In order to infer realistic nonuniformities in the model parameters, the uniform version of the model is first fitted to data recorded from 98 normal subjects in a waking, eyes-closed state. This yields a set of parameters at each of five electrode sites along the midline. The inferred parameter nonuniformities are consistent with anatomical and physiological constraints. Introducing these spatial profiles into the full nonuniform model then quantitatively reproduces observed site-dependent variations in the alpha power and frequency. The results confirm that the frequency shift is mainly due to a decrease in the corticothalamic propagation delay, but indicate that the delay nonuniformity cannot account for the observed occipital increase in alpha power; the occipital alpha dominance is due to decreased cortical gains and increased thalamic gains in occipital regions compared to frontal ones.

Handedness is mainly associated with an asymmetry of corticospinal excitability and not of transcallosal inhibition

OBJECTIVE

The study aims to compare transcallosal inhibition (TI), as assessed by the paired-pulse transcranial magnetic stimulation (TMS) technique, in a sample of right-handed subjects (RH) and left-handed subjects (LH). Motor thresholds (MTs) and motor evoked potential (MEP) amplitudes were also measured in the two groups, as an index of corticospinal activity.

METHODS

Thirty-two normal subjects (16 RH and 16 LH) were recorded with a paired-pulse TMS paradigm (intensity of both pulses=120% of MT). The inter-stimulus intervals (ISIs) were 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 ms for both motor cortices, and MEP responses were recorded from the abductor digiti minimi muscles.

RESULTS

Both groups showed a clear TI centred around the 12 ms ISI, but no difference was found as a function of handedness or of hemisphere. On the other hand, the two groups differed in terms of corticospinal activity, since the hand motor dominant hemisphere had lower MTs than the non-dominant one in LH, and larger MEP amplitudes for the right hand were found in RH.

CONCLUSIONS

Results point to a functional asymmetry of the motor cortex on the hand-dominant versus the non-dominant hemisphere, while handedness does not seem associated with functional differences in callosal inhibition, as measured by the inter-hemispheric paired-pulse TMS technique.

The nature of arousal in sleep

The role of arousals in sleep is gaining interest among both basic researchers and clinicians. In the last 20 years increasing evidence shows that arousals are deeply involved in the pathophysiology of sleep disorders. The nature of arousals in sleep is still a matter of debate. According to the conceptual framework of the American Sleep Disorders Association criteria, arousals are a marker of sleep disruption representing a detrimental and harmful feature for sleep. In contrast, our view indicates arousals as elements weaved into the texture of sleep taking part in the regulation of the sleep process. In addition, the concept of micro-arousal (MA) has been extended, incorporating, besides the classical low-voltage fast-rhythm electroencephalographic (EEG) arousals, high-amplitude EEG bursts, be they like delta-like or K-complexes, which reflects a special kind of arousal process, mobilizing parallely antiarousal swings. In physiologic conditions, the slow and fast MA are not randomly scattered but appear structurally distributed within sleep representing state-specific arousal responses. MA preceded by slow waves occurs more frequently across the descending part of sleep cycles and in the first cycles, while the traditional fast type of arousals across the ascending slope of cycles prevails during the last third of sleep. The uniform arousal characteristics of these two types of MAs is supported by the finding that different MAs are associated with an increasing magnitude of vegetative activation ranging hierarchically from the weaker slow EEG types (coupled with mild autonomic activation) to the stronger rapid EEG types (coupled with a vigorous autonomic activation). Finally, it has been ascertained that MA are not isolated events but are basically endowed with a periodic nature expressed in non-rapid eye movement (NREM) sleep by the cyclic alternating pattern (CAP). Understanding the role of arousals and CAP and the relationship between physiologic and pathologic MA can shed light on the adaptive properties of the sleeping brain and provide insight into the pathomechanisms of sleep disturbances. Functional significance of arousal in sleep, and particularly in NREM sleep, is to ensure the reversibility of sleep, without which it would be identical to coma. Arousals may connect the sleeper with the surrounding world maintaining the selection of relevant incoming information and adapting the organism to the dangers and demands of the outer world. In this dynamic perspective, ongoing phasic events carry on the one hand arousal influences and on the other elements of information processing. The other function of arousals is tailoring the more or less stereotyped endogenously determined sleep process driven by chemical influences according to internal and external demands. In this perspective, arousals shape the individual course of night sleep as a variation of the sleep program.

Eyelid movements measured by Nightcap predict slow eye movements during quiet wakefulness in humans

A precipitous decline in eyelid movements (ELMs) has been shown to be a highly reliable indicator of sleep onset. While ELMs correlate well with eye movements during waking and rapid eye movement (REM) sleep, the eye sensor remains silent during the period of slow eye movements (SEMs) typical of sleep onset. If the ELM density (e.g. ELMs per minute) dropped simultaneously with the appearance of SEMs prior to sleep onset, it could be a promising tool for identifying decreases in alertness prior to overt sleep onset. The present study was designed to determine whether the presence of SEMs in the transitional period preceding stage 1 sleep is reflected in decreases in ELM density. ELM densities were computed for 2.5-s epochs with and without SEMs, as well as for 15-s epochs. Decreases in ELM density not only were an excellent correlate of the appearance of SEMs during wakefulness with closed eyes, but also a good predictor of their occurrence (c. 82% accuracy) at a time resolution of 2.5 s. Based on these results, we conclude that ELM density reliably predicts moderate changes in the level of alertness during quiet wakefulness.

Paradoxes of the first-night effect: a quantitative analysis of antero-posterior EEG topography

OBJECTIVE

The first-night effect (FNE) is a common issue in sleep research. Being considered fragmented and poorly efficient, the adaptation night is discarded for data analysis. The present study aims to provide a quantitative and topographical EEG analysis of this phenomenon.

METHODS

Eight healthy subjects slept for two consecutive nights (adaptation (AD) and baseline (BSL)), and their polysomnography was visually scored and then submitted to spectral power analysis.

RESULTS

The results showed a decreased quality and quantity of first-night sleep as indicated by more stage 1 and intrasleep wake, paralleled by a reduced sleep efficiency and a longer sleep onset latency. On the other hand, EEG quantitative data showed a more complex and apparently paradoxical picture. An increase in delta power was observed, particularly over the central areas during the first night, paralleled by an increased power in beta bin frequencies solely at posterior scalp locations.

CONCLUSIONS

These results have been interpreted as caused by, respectively, a reduced total sleep time during the adaptation night and a cortical hyperactivity, typical of psychophysiological insomnia. The present results confirm the need to exclude the laboratory sleep adaptation night from data analysis since it is not a reliable index of sleep on subsequent nights as regards both visual scoring and quantitative EEG analysis. Finally, regional differences between REM and NREM sleep have been confirmed.

SIGNIFICANCE

This is the first attempt to evaluate the FNE with a quantitative approach to the antero-posterior EEG topography, providing both a Hz-by-Hz and a classical EEG band-based analysis.

Intracortical inhibition and facilitation upon awakening from different sleep stages: a transcranial magnetic stimulation study

Intracortical facilitation and inhibition, as assessed by the paired-pulse transcranial magnetic stimulation technique with a subthreshold conditioning pulse followed by a suprathreshold test pulse, was studied upon awakening from REM and slow-wave sleep (SWS). Ten normal subjects were studied for four consecutive nights. Intracortical facilitation and inhibition were assessed upon awakening from SWS and REM sleep, and during a presleep baseline. Independently of sleep stage at awakening, intracortical inhibition was found at 1-3-ms interstimulus intervals and facilitation at 7-15-ms interstimulus intervals. Motor thresholds were higher in SWS awakenings, with no differences between REM awakenings and wakefulness, while motor evoked potential amplitude to unconditioned stimuli decreased upon REM awakening as compared to the other conditions. REM sleep awakenings showed a significant increase of intracortical facilitation at 10 and 15 ms, while intracortical inhibition was not affected by sleep stage at awakening. While the dissociation between motor thresholds and motor evoked potential amplitudes could be explained by the different excitability of the corticospinal system during SWS and REM sleep, the heightened cortical facilitation upon awakening from REM sleep points to a cortical motor activation during this stage.

Event-related potentials and EMDR treatment of post-traumatic stress disorder

Ten patients suffering from post-traumatic stress disorder (PTSD) following a severe traumatic event, were assessed with event-related brain potentials (ERPs) in a modified oddball paradigm containing auditory standard, target, and novel tones. ERPs were assessed before and after a treatment session using the eye movement desensitization and reprocessing method. Compared to a control group that underwent sham treatment, ERPs of the patients showed a reduction of the P3a component in the post-treatment recording, suggesting a reduced orienting to novel stimuli and reduced arousal level after the treatment. Moreover, psychometric assessment revealed a marked improvement of the PTSD symptoms after treatment.

Rapid eye movement density shows trends across REM periods but is uncorrelated with NREM delta in young and elderly human subjects

Saccade-like eye movements are the most prominent phasic component of rapid eye movement (REM) sleep. Eye movement density (EMD) appears to be negatively related to sleep depth. Thus, EMD is depressed by sleep deprivation. We sought to determine in 19 young normal (YN) and 19 elderly normal (EN) subjects: (a) whether EMD is correlated with delta EEG in baseline sleep; (b) whether EMD is increased by daytime naps; and (c) whether EMD patterns across sleep cycles differ in the two age groups. Subjects participated in four separate 2-day recording sessions, each consisting of a baseline night, a daytime nap, and post nap night. EMD was measured as 0.3-2 Hz integrated amplitude (IA)/20 s stage REM. EMD was not correlated with rate of non rapid eye movement (NREM) delta production (power/min) in the baseline sleep of either group. Changes in EMD and delta power/min on post nap nights also were uncorrelated. These data indicate that very strong changes in sleep depth (state) are required to overcome the individual stability (traits) of NREM delta and eye movement density. ANOVA for EMD across REM periods 1-4 showed a significant cycle effect and a significant age x cycle interaction. These effects were mainly due to YNs having depressed EMD in the first REM period, likely due to the low arousal level early in sleep in these subjects. Compared with waking saccades the saccade eye movements of REM sleep have received little investigation. Further study of these movements could shed new light on neurophysiology of REM sleep. Such studies might also be clinically useful because the density of these movements appears to be related to depression and (independently) to cognitive function in individuals with brain impairment.