Time of day is associated with paradoxical reductions in global signal fluctuation and functional connectivity | bioRxivPosted: May 31, 2019
Early childhood adversity associations with nightmare severity andsleep spindles*
Objective: Childhood adversity figures prominently in the clinical histories of children and adolescents suffering from a panoply of physical, mental or sleep disorders, including posttraumatic stress disorder. But the nature and prevalence of early adversity in the case of idiopathic nightmare-prone individuals have received little study. We characterize the types and frequencies of self-reported childhood adversity for nightmare-prone individuals using the developmentally sensitive Traumatic Antecedents Questionnaire (TAQ) and assess relationships between separation adversity and sleep spindles. Method: The TAQ was administered to 73 non-treatment-seeking volunteers with frequent idiopathic nightmares and 67 healthy controls. Nightmare severity, anxiety, depression, alexithymia and past and present sleep disorders were also assessed. Sleep was recorded with polysomnography (PSG) for 90 participants and sleep spindles were assessed for 63. Results: Nightmare-prone participants scored higher on most TAQ measures, including adversity at 0-6 years of age. TAQ-derived scales assessing traumatic and nontraumatic forms of adversity were both elevated for nightmare-prone participants; for 0-6 year estimates, nontraumatic adversity was associated with nightmares independent of trauma adversity. Group differences were only partially mediated by current psychopathology symptoms and were largely independent of nightmare frequency but not of nightmare distress. Adversity/nightmare relationships were graded differentially for the two study groups. Separation adversity at 0-6 years of age correlated with current sleep spindle anomalies, in particular, lower slow spindle density, an anomaly known to index both psychopathology and early nightmare-onset. Conclusions: Self-reported adversity occurring as young as 0-6 years of age is associated with nightmare severity and sleep spindle anomalies. Adversity-linked nightmares may reflect pathophysiological mechanisms common also to the nightmares of pre-clinical and full-blown post-traumatic stress disorder.
Sleep increases chromosome dynamics to enable reduction of accumulating DNA damage in single neurons | Nature CommunicationsPosted: March 16, 2019
Sleep is essential to all animals with a nervous system. Nevertheless, the core cellular function of sleep is unknown, and there is no conserved molecular marker to define sleep across phylogeny. Time-lapse imaging of chromosomal markers in single cells of live zebrafish revealed that sleep increases chromosome dynamics in individual neurons but not in two other cell types. Manipulation of sleep, chromosome dynamics, neuronal activity, and DNA double-strand breaks (DSBs) showed that chromosome dynamics are low and the number of DSBs accumulates during wakefulness. In turn, sleep increases chromosome dynamics, which are necessary to reduce the amount of DSBs. These results establish chromosome dynamics as a potential marker to define single sleeping cells, and propose that the restorative function of sleep is nuclear maintenance.