Sleep highlights

Abstract

This issue of the Journal of Sleep Research contains studies which contribute to our understanding of the role of sleep in shaping our lives. At the basic level, Hagewoud et al. (2010) show how, in rats, sleep deprivation not only reduces expressed fear after fear conditioning through a mild foot shock but also attenuates the ‘stress’ response as indexed by corticosterone and reduces the phosphorylation of cAMP response element binding protein (CREB) in the hippocampus and amygdala. Thus the absence of sleep shortly after an unpleasant experience will reduce the strength of the memory and associated physiological and molecular responses. Whether or not this is desirable, depends very much on the situation but there is no doubt that there are certain experiences we may want to forget or ‘repress’ as Freud may have said. Fischer et al. (2010) report intriguing results from an elegant study investigating the role of sleep in ‘directed forgetting’. In essence, the data seem to imply that if you are trying to forget something avoid rapid eye movement (REM) sleep. The two studies contribute to the ever more rich and complex picture of sleep and memory. How good are we at making decisions under time pressure in an emergency situation when we are woken up in the middle of the night? Horne and Moseley (2011) report that junior officer reservists are not very good at it at all. Although the relative contribution of circadian phase, sleep deprivation and sleep inertia remains to be established, these results highlight the impact of sleep inertia and circadian phase on some of the executive functioning tasks we have to conduct in the real world. How good are new parents at switching between tasks? Plessow et al. (2010) present data which show that new parents sleeping for fewer than 7 h find this more difficult than those sleeping more. The effects are subtle and highlight the need for a comprehensive assessment of waking performance. Several health outcome measures have been shown to be associated with self-reported sleep duration (Cappuccio et al., 2010; Gallicchio and Kalesan, 2009). Two previous studies in this journal indicated that self-reported sleep duration may also be associated with cognitive performance (Faubel et al., 2009; Kronholm et al., 2009). Kronholm et al. (2010) now present results from a sleep-duration–cognitive epidemiological approach in which simple reaction time and choice reaction time were the main outcome measures, thereby providing an important link between epidemiology and laboratory studies. The data show convincingly that both short and long sleep duration are associated with long reaction times. Of note is that the authors prefer to interpret reaction times as an indicator of ‘physiological integrity of the brain’ rather than an indicator of ‘…the individual’s acute and reversible state of vigilance’. Many novel approaches to monitor sleep in non-laboratory settings are currently under development (Van de Water et al., 2011), and it will be important to test and validate these approaches. De Chazal et al. (2010) present results based on motion detection through ultra low-power reflected radiofrequency waves. The approach allows for identification of sleep and wakefulness and also of direct visualization of respiratory movement signals. Comparison of sensitivity and specificity of this approach with other alternatives to full polysomnography, e.g. actigraphy and single-channel electroencephalogram (EEG), is discussed. Although continuous positive airway pressure is used widely in the treatment for obstructive sleep aponea, compliance is poor. Ryan et al. (2010) report the results of a small randomized cross-over trial of delivery of continuous positive airway pressure through a standard nasal mask or a nasal pillow. No differences in either effectiveness or compliance were reported. Sleep and delivery of therapy of sleep disorders remains challenging.