Nicola Cellini

Direct comparison of two actigraphy devices with polysomnographically recorded naps in healthy young adults.

The last 20 yrs have seen a marked increase in studies utilizing actigraphy in free-living environments. The aim of the present study is to directly compare two commercially available actigraph devices with concurrent polysomnography (PSG) during a daytime nap in healthy young adults. Thirty healthy young adults, ages 18–31 (mean 20.77 yrs, SD 3.14 yrs) simultaneously wore AW-64 and GT3X+ devices during a polysomnographically recorded nap. Mann-Whitney U (M-U) test, intraclass correlation coefficients, and Bland-Altman statistic were used to compare total sleep time (TST), sleep onset latency (SOL), wake after sleep onset (WASO), and sleep efficiency (SE) between the two actigraphs and PSG. Epoch-by-epoch (EBE) agreement was calculated to determine accuracy, sensitivity, specificity, predictive values for sleep (PVS) and wake (PVW), and kappa and prevalence- and bias-adjusted kappa (PABAK) coefficients. All frequency settings provided by the devices were examined. For both actigraphs, EBE analysis found accuracy, sensitivity, specificity, PVS, and PVW comparable to previous reports of other similar devices. Kappa and PABAK coefficients showed moderate to high agreement with PSG depending on device settings. The GT3X+ overestimated TST and SE, and underestimated SOL and WASO, whereas no significant difference was found between AW-64 and PSG. However, GT3X+ showed overall better EBE agreements to PSG than AW-64. We conclude that both actigraphs are valid and reliable devices for detecting sleep/wake diurnal patterns. The choice between devices should be based on several parameters as reliability, cost of the device, scoring algorithm, target population, experimental condition, and aims of the study (e.g., sleep and/or physical activity). (Author correspondence: smednick@ucr.edu)

Nocturnal cardiac autonomic profile in young primary insomniacs and good sleepers

We investigated cardiac vagal and sympathetic activity in 13 young primary insomniacs (PI; 24.4±1.6years) and 14 good sleepers (GS; 23.3±2.5years) during nocturnal sleep. Pre-ejection period (PEP; inversely related to beta-adrenergic sympathetic activity), interval between consecutive R-waves (RR), and vagal-related indices of time- and frequency-domain heart rate variability were computed during pre-sleep wakefulness and undisturbed arousal-free sleep stages (N2, SWS, REM) as well as across the whole night irrespective of the presence of disruptive sleep events (e.g. sleep arousals/awakenings) and/or sleep stage transitions. Groups exhibited a similar vagal activity throughout each undisturbed sleep stage as well as considering the whole night, with a higher modulation during sleep compared to prior wakefulness. However, PEP was constantly shorter (higher sympathetic activity) during pre-sleep wakefulness and each sleep stage in PI compared to GS. Moreover, pre-sleep RR intervals were positively associated with sleep efficiency and negatively associated with wake after sleep onset in PI. Altogether our findings indicated a dysfunctional sympathetic activity but a normal parasympathetic modulation before and during sleep in young adults with insomnia.

Sleep before and after learning promotes the consolidation of both neutral and emotional information regardless of REM presence

Sleep may play a role in consolidating emotional memories. However, studies on the effects of REM sleep on negative vs. neutral memories have produced inconsistent evidence. Here, we assess the role of NREM and REM sleep before and after learning in promoting the consolidation of neutral and arousing pleasant and unpleasant memories. Forty-six (32 F) healthy university students were exposed to a set of pictures at 1:00PM (Session 1) and to an equivalent set at 4:45PM (Session 2). All the pictures in Session 1 and Session 2 were presented again, intermixed with new similar pictures at 5:15PM in a memory recognition task. Following Session 1, participants took a 90/120-min nap (NAP group), while 16 participants remained awake (WAKE group). Via polysomnographic recording, the NAP group was segregated into REM (N=14) and NoREM groups (N=16). Indices of memory consolidation for both stimuli presented before (discriminability of Session 1 pictures in Session 3) and after sleep (discriminability of Session 2 pictures in Session 3) were calculated. Memory consolidation for pictures presented both before and after the sleep period was higher in the NAP group as compared to the WAKE group, but no differential role of REM sleep emerged. A memory consolidation advantage was evident for neutral over pleasant (but not unpleasant) pictures. Taken together, these results indicate that a daytime nap (with or without REM sleep) facilitates consolidation of declarative memories presented before and after sleep irrespective of their valence.

Polysomnographic validation of a wireless dry headband technology for sleep monitoring in healthy young adults.

The present study aimed to explore the validity and reliability of a wireless dry headband technology for sleep monitoring (WS), through a comparison with concurrent polysomnographic (PSG) recording in healthy young adults. Eleven volunteers (7 females; mean age±SD: 24.75±3.62years) took part in the study, wearing the WS for two overnight PSG recordings in the sleep laboratory. The WS was compared to PSG in the identification of wake, light, deep and REM sleep. The WS sensitivity and specificity were 97.6% and 56.1%, respectively. The WS agreement with PSG, measured by Cohens kappa, was 0.56 for light sleep, 0.70 for deep sleep, and 0.67 for REM sleep. The present results showed that the agreement ranged from moderate to high between PSG and the WS, while wakefulness detection was observed to be a limitation of the WS.

Hemodynamic and autonomic modifications during sleep stages in young hypotensive women

This study examined cardiovascular activity and autonomic involvement during sleep in essential hypotension. We compared young female hypotensives and normotensives using ambulatory blood pressure monitoring, impedance cardiography, and frequency-domain analysis of heart rate variability during a night of polysomnographic recording. Hypotensives, as compared to normotensives, exhibited lower blood pressure, reduced myocardial contractility and reduced sympathovagal balance across the whole night. Both groups exhibited a reduction in cardiovascular involvement from wake to sleep with similar cardiovascular activity during wake and REM. No group difference was observed in sleep architecture suggesting similar sleeping quality in hypotensives and normotensives. The lower blood pressure and reduced myocardial contractility associated with a lower sympathovagal balance in hypotensives, as compared to normotensives, suggest a night-time hypoactivation of the cardiovascular system supporting the hypothesis of impairment in autonomic control in essential hypotension.

Cardiovascular down‐regulation in essential hypotension: Relationships with autonomic control and sleep

In this work, we aimed to clarify the autonomic involvement in the cardiovascular down-regulation in essential hypotension. The relationships between cardiovascular response and sleep quality were also examined. Thirteen female hypotensives and 13 female normotensives performed a stress task followed by polysomnography. Measures derived from blood pressure monitoring, impedance cardiography, and heart rate variability were collected. Hypotensives exhibited lower cardiovascular and autonomic activation than controls during the task. While a better sleep quality (i.e., higher sleep efficiency and lower nocturnal wakefulness) correlated with a reduced reactivity in normotensives, the opposite pattern occurred in hypotensives. The results suggest that a blunted response in both autonomic branches underlies the cardiovascular hypoactivation in hypotension. Further, good sleep seems to be associated with optimal levels of physiological reactivity.

Impaired Off-Line Motor Skills Consolidation In Young Primary Insomniacs

Compelling evidence indicates that sleep can facilitate the off-line consolidation of declarative, perceptual, emotional and procedural memories. Here we assessed the sleep-related off-line consolidation of motor skills in 13 young primary insomniacs (23.31±2.5 yrs) compared to 13 healthy sleepers (24.31±1.6 yrs) using the sequential finger tapping task. During a training session insomniacs performed less correct sequences than controls. However, both groups exhibited similar on-line motor learning in the pre-sleep evening session. After a night of sleep, healthy controls improved their performance, indicating an overnight effect of sleep on motor skills consolidation. In contrast, insomniacs failed to exhibit a sleep-related enhancement in memory performance indicating impairment in the off-line motor skills consolidation process. Our results suggest that young adults with insomnia experience impaired off-line memory consolidation which seems not to be associated with reduced ability to acquire new motor information.

Cardiac autonomic profile during rest and working memory load in essential hypotensive women

To our knowledge, no previous study has provided reliable data supporting a different modulation of the Neurovegetative system in essential hypotension. Our purpose was to provide, in essential hypotensive women compared to normotensives, evidence of a distinct sympathetic and parasympathetic cardiac control. Cardiovascular and autonomic indexes derived by impedance cardiography (heart rate, HR; pre-ejection period, PEP), photoplethysmographic technique (blood pressure, BP) and heart rate variability analysis (high and low frequencies power, HF and LF) were continuously collected during rest and mental stress condition. Hypotensives, compared to normotensives, exhibited prolonged PEP (low sympathetic tone) and elevated HF (high vagal involvement) during rest. In addition, they showed cardiovascular (reduced increases in BP and HR) and sympathetic (lower reductions of PEP) hypo-reactivity to the task. Furthermore, a lower sympathetic reactivity in hypotensives was associated to a poorer task performance. Essential hypotension was characterized by a low sympathetic and high parasympathetic tone. In addition, a reduced sympathetic nervous system reactivity suggests the main role of the Neurovegetative system in mediating the relationship between blood pressure and cognitive performance in hypotensives.

Validation of an Automated Wireless System for Sleep Monitoring During Daytime Naps

An automated wireless system (WS) for sleep monitoring was recently developed and validated for assessing nighttime sleep. Here, we aimed to evaluate the validity of the WS to correctly monitor daytime sleep during naps compared to polysomnography (PSG). We found that the WS underestimated wake, sleep onset latency, and wake after sleep onset. Meanwhile, it overestimated total sleep time, sleep efficiency, and duration of REM sleep. Sensitivity was moderate for wake (58.51%) and light sleep (66.92%) and strong for deep sleep (83.46%) and REM sleep (82.12%). These results demonstrated that the WS had a low ability to detect wake and systematically overscored REM sleep, implicating the WS as an inadequate substitute for PSG in diagnosing sleep disorders or for research in which sleep staging is essential.

The Temporal Dynamics of Motor Memory across Wake and Sleep.

People learn how to write, play piano, and ride a bicycle through repetitive practice. The acquisition of these procedural motor skills has been thought to occur in stages ([Dayan and Cohen, 2011][1]), with an initial fast learning phase characterized by rapid within-session improvement before