Muller et al. eLife 2016;5:e17267. DOI: 10.7554/eLife.17267
Abstract During sleep, the thalamus generates a characteristic pattern of transient, 11-15 Hz
sleep spindle oscillations, which synchronize the cortex through large-scale thalamocortical loops.
Spindles have been increasingly demonstrated to be critical for sleep-dependent consolidation of
memory, but the specific neural mechanism for this process remains unclear. We show here that
cortical spindles are spatiotemporally organized into circular wave-like patterns, organizing
neuronal activity over tens of milliseconds, within the timescale for storing memories in large-scale
networks across the cortex via spike-time dependent plasticity. These circular patterns repeat over
hours of sleep with millisecond temporal precision, allowing reinforcement of the activity patterns
through hundreds of reverberations. These results provide a novel mechanistic account for how
global sleep oscillations and synaptic plasticity could strengthen networks distributed across the
cortex to store coherent and integrated memories.
This review summarises the literature on shift work and its relation to insufficient sleep, chronic diseases, and accidents. It is based on 38 meta-analyses and 24 systematic reviews, with additional narrative reviews and articles used for outlining possible mechanisms by which shift work may cause accidents and adverse health. Evidence shows that the effect of shift work on sleep mainly concerns acute sleep loss in connection with night shifts and early morning shifts. A link also exists between shift work and accidents, type 2 diabetes (relative risk range 1.09-1.40), weight gain, coronary heart disease (relative risk 1.23), stroke (relative risk 1.05), and cancer (relative risk range 1.01-1.32), although the original studies showed mixed results. The relations of shift work to cardiometabolic diseases and accidents mimic those with insufficient sleep. Laboratory studies indicate that cardiometabolic stress and cognitive impairments are increased by shift work, as well as by sleep loss. Given that the health and safety consequences of shift work and insufficient sleep are very similar, they are likely to share common mechanisms. However, additional research is needed to determine whether insufficient sleep is a causal pathway for the adverse health effects associated with shift work.