Night-time sleep and daytime sleepiness in narcolepsy

This report describes night-time sleep and daytime sleepiness in a large (N=530) sample of patients meeting the International Classification of Sleep Disorders criteria for diagnosis of narcolepsy. Sleep data were obtained from polysomnographic recordings on two consecutive nights. Sleepiness was assessed using the Multiple Sleep Latency Test, the Maintenance of Wakefulness Test and the Epworth Sleepiness Scale. Analysis revealed that sleep was mild to moderately disturbed on both recording nights. A first-night effect was suggested by decreased REM latency and increased percentage REM and slow-wave sleep on the second night. Sleepiness and sleep disturbance varied across patient subgroups created based on patient ethnicity and on the presence/absence of cataplexy, sleep apnoea, and periodic limb movements. Covariation of sleep and sleepiness measures across patients was significant but weak. Strong association was found between subgroup means of sleep and sleep disturbance measures. The findings reported here show that sleepiness and sleep disturbance vary across patient subgroups and that sleep disturbance is related to, although unable to account, for the pathological sleepiness of narcolepsy.

The effects of active and passive stimulation on chemosensory event-related potentials

During normal olfaction, stimulation is dependent upon nasal inhalation. When collecting chemosensory event-related potentials (CSERPs), inhalations may produce artifacts such as respiration-related brain potentials that confound interpretation of the data. To avoid this type of artifact, CSERPs have often been collected using stimulation that is independent of respiratory cycle. It is possible, however, that inspirations prime the olfactory tract for odor input, and traditional CSERP data acquisition techniques, obscure this neural preparation. To investigate this question, twelve subjects were tested using two different approaches to stimulation. Odorants (butanol 2% and 4%) were introduced into a warmed and humidified air stream and delivered to one nostril through a cannula. In one condition, subjects mouth-breathed and stimuli occurred asynchronously with respiratory cycle (passive). In the other condition, subjects inhaled through the nose and stimuli were delivered synchronously with nasal inhalations (active). CSERP data were collected from thirty scalp sites for 3 s following stimulation. Data were corrected for eye movements, smoothed, and averaged. Maximal amplitudes for an early negativity (N1) and later positivity (P2) were determined and submitted to separate analyses of variance. These analyses indicated that administration technique interacted with both odor concentration and recording site. Additionally, amplitude of P2 was greater in the passive condition. Such results suggest that the two administration techniques produce different neural processing of olfactory stimuli and that the passive technique may be better suited for determination of the integrity of the olfactory tract for single subjects because of its greater amplitude.

Effect of sleep deprivation on NREM sleep ERPs and related activity at sleep onset

This research assessed the impact of one night of sleep deprivation on the amplitudes of NREM-sleep event-related potentials (NREM ERPs) and on the frequency of occurrence of related electroencephalogram activity including sleep spindles, arousals, K-complexes, and vertex sharp waves (VSWs). The NREM ERPs identified included P220, N350, P450, N550 and P900. During a pre-deprivation night, ten subjects took two 20-min naps separated by a 20-min break at their normal bedtime. Brief tones were presented at three intensity levels (60, 75 and 90 dB) with a 5-s interstimulus interval. Following these naps, subjects were kept awake until their normal bedtime the following day. At that time, they repeated the two-nap procedure. The ERPs obtained for each tone and wake/sleep state for pre- and post-deprivation conditions were analyzed using repeated measures statistical procedures. As anticipated, NREM ERP amplitudes recorded both pre- and post-deprivation increased with tone intensity and with approaching sleep. Also, sleep deprivation was associated with more rapid sleep onset, reduced arousability, and greater spindle production. While sleep deprivation had no effect on the amplitude of P220. Post-deprivation amplitudes of N350, N550 and P900 were greater, especially following the 90-dB tone. There was a corresponding increase in VSWs and K-complexes. These findings are inconsistent with the view that NREM ERPs reflect arousal. The underlying mechanism(s) may facilitate initiation and maintenance of sleep.

Laser cooling of antihydrogen atoms

The photon-the quantum excitation of the electromagnetic field-is massless but carries momentum. A photon can therefore exert a force on an object upon collision1. Slowing the translational motion of atoms and ions by application of such a force2,3, known as laser cooling, was first demonstrated 40 years ago4,5. It revolutionized atomic physics over the following decades6-8, and it is now a workhorse in many fields, including studies on quantum degenerate gases, quantum information, atomic clocks and tests of fundamental physics. However, this technique has not yet been applied to antimatter. Here we demonstrate laser cooling of antihydrogen9, the antimatter atom consisting of an antiproton and a positron. By exciting the 1S-2P transition in antihydrogen with pulsed, narrow-linewidth, Lyman-α laser radiation10,11, we Doppler-cool a sample of magnetically trapped antihydrogen. Although we apply laser cooling in only one dimension, the trap couples the longitudinal and transverse motions of the anti-atoms, leading to cooling in all three dimensions. We observe a reduction in the median transverse energy by more than an order of magnitude-with a substantial fraction of the anti-atoms attaining submicroelectronvolt transverse kinetic energies. We also report the observation of the laser-driven 1S-2S transition in samples of laser-cooled antihydrogen atoms. The observed spectral line is approximately four times narrower than that obtained without laser cooling. The demonstration of laser cooling and its immediate application has far-reaching implications for antimatter studies. A more localized, denser and colder sample of antihydrogen will drastically improve spectroscopic11-13 and gravitational14 studies of antihydrogen in ongoing experiments. Furthermore, the demonstrated ability to manipulate the motion of antimatter atoms by laser light will potentially provide ground-breaking opportunities for future experiments, such as anti-atomic fountains, anti-atom interferometry and the creation of antimatter molecules.

Sympathetic cooling of positrons to cryogenic temperatures for antihydrogen production

The positron, the antiparticle of the electron, predicted by Dirac in 1931 and discovered by Anderson in 1933, plays a key role in many scientific and everyday endeavours. Notably, the positron is a constituent of antihydrogen, the only long-lived neutral antimatter bound state that can currently be synthesized at low energy, presenting a prominent system for testing fundamental symmetries with high precision. Here, we report on the use of laser cooled Be+ ions to sympathetically cool a large and dense plasma of positrons to directly measured temperatures below 7 K in a Penning trap for antihydrogen synthesis. This will likely herald a significant increase in the amount of antihydrogen available for experimentation, thus facilitating further improvements in studies of fundamental symmetries.

Observation of the effect of gravity on the motion of antimatter

Einstein's general theory of relativity from 19151 remains the most successful description of gravitation. From the 1919 solar eclipse2 to the observation of gravitational waves3, the theory has passed many crucial experimental tests. However, the evolving concepts of dark matter and dark energy illustrate that there is much to be learned about the gravitating content of the universe. Singularities in the general theory of relativity and the lack of a quantum theory of gravity suggest that our picture is incomplete. It is thus prudent to explore gravity in exotic physical systems. Antimatter was unknown to Einstein in 1915. Dirac's theory4 appeared in 1928; the positron was observed5 in 1932. There has since been much speculation about gravity and antimatter. The theoretical consensus is that any laboratory mass must be attracted6 by the Earth, although some authors have considered the cosmological consequences if antimatter should be repelled by matter7-10. In the general theory of relativity, the weak equivalence principle (WEP) requires that all masses react identically to gravity, independent of their internal structure. Here we show that antihydrogen atoms, released from magnetic confinement in the ALPHA-g apparatus, behave in a way consistent with gravitational attraction to the Earth. Repulsive 'antigravity' is ruled out in this case. This experiment paves the way for precision studies of the magnitude of the gravitational acceleration between anti-atoms and the Earth to test the WEP.

0180 Sleep, Sleepiness, and Sleep Hygiene Related to Nomophobia (No Mobile Phone Phobia)

Introduction

Previously, active phone use at bedtime has been implicated in disrupted sleep and related complaints. To improve sleep, a recommendation following such findings is limiting phone use before and during bedtime. However, for those with the characteristic of “nomophobia”, fear of being out of mobile phone contact, this recommendation could exacerbate anxiety at and around bedtime and disrupt, rather than improve, sleep. In 2012, an estimated 77% of 18-24-year-olds could be identified as nomophobic. Because of the prevalence of nomophobia and its possible interaction with sleep, we explored the existence of nomophobia in a college-age population and its relationship to sleep, sleepiness, and sleep hygiene behaviors.

Methods

327 university students (age: M=19.7 years, SD=3.78) recruited from introductory psychology courses and campus newsletters were given extra credit or a chance to win $25 gift cards for participation. Participants completed demographic information, the Nomophobia Questionnaire (NMP-Q), the Epworth Sleepiness Scale (ESS), the Pittsburgh Sleep Quality Index, questions regarding associated features of inadequate sleep hygiene, and the Sleep Hygiene Index. Additional sleep hygiene questions assessed frequency of active and passive technology use during sleep time.

Results

89.4% of the participants had moderate or severe nomophobia. Greater nomophobia was significantly related to greater daytime sleepiness (ESS) (r(293)=.150, p<.05), associated features of poor sleep (daytime sleepiness: r(297)=.097, p<.05, and avolition: r(297)=.100, p<.05), more maladaptive sleep hygiene behaviors including active technology use during sleep time (r(298)=.249, p<.05), long daytime naps, inconsistent wake and bed times, using bed for non-sleep purposes, uncomfortable bed, and bedtime cognitive rumination (r’s=0.097 to 0.182).

Conclusion

Most participants experienced moderate to severe nomophobia with greater nomophobia associated with greater sleepiness, avolition, and poorer sleep hygiene. Nomophobia is likely to be an important consideration when treating sleep disorders and/or making any sleep hygiene recommendations.

Support

Hendrix College Charles Brewer Fund for Psychology

0194 Bedtime Technology Use and New Questions for the Sleep Hygiene Index

Introduction

We examined the relationship between bedtime active and passive social technology use (self and bedpartner) and daytime sleepiness/sleep. We generated questions to differentiate participants with and without bedpartners and updated passive personal, active bedpartner, and passive bedpartner social technology questions of the Sleep Hygiene Index.

Methods

327 students (age: M=19.7 years, SD=3.78) recruited through psychology courses and campus newsletters received extra credit or chances to win $25 gift cards. Participants completed demographic information, the Epworth Sleepiness Scale (ESS), the Pittsburgh Sleep Quality Index, questions regarding associated features of inadequate sleep hygiene, and the Sleep Hygiene Index. Five questions assessed active and passive social technology use, presence of a bedpartner, and awareness of bedpartner active and passive social technology use during sleep time.

Results

61.8% and 62.7% of students reported frequently or always using active and passive bedtime social technology, respectively; and 23.5% and 29.1% reported noticing a partner’s active or passive use. More frequent active technology use was significantly related to greater daytime sleepiness (ESS) (r(305)=.193, p<.05), sleep disturbances (PSQI-global: r(302)=.120, p<.05), and associated features of inadequate sleep hygiene (daytime sleepiness, worry about sleep, mood disturbance, avolition, and reduced cognition (r(306)=.212, p<.05)). Neither passive use nor passive or active partner use was significantly related to any sleep/sleepiness variables.

Conclusion

We continue to find students are frequent users of bedtime social technology which is related to daytime sleepiness, disrupted sleep, and related complaints. Passive and partner active/passive bedtime technology use may not have a significant impact on daytime sleepiness. It is possible younger participants are not good judges of passive or partner technology use or this younger population is resilient to these disruptions.

Support

none