Experimental ‘Jet Lag’ Inhibits Adult Neurogenesis and Produces Long-Term Cognitive Deficits in Female Hamsters

Abstract

BackgroundCircadian disruptions through frequent transmeridian travel, rotating shift work, and poor sleep hygiene are associated with an array of physical and mental health maladies, including marked deficits in human cognitive function. Despite anecdotal and correlational reports suggesting a negative impact of circadian disruptions on brain function, this possibility has not been experimentally examined.Methodology/Principal FindingsIn the present study, we investigated whether experimental ‘jet lag’ (i.e., phase advances of the light∶dark cycle) negatively impacts learning and memory and whether any deficits observed are associated with reductions in hippocampal cell proliferation and neurogenesis. Because insults to circadian timing alter circulating glucocorticoid and sex steroid concentrations, both of which influence neurogenesis and learning/memory, we assessed the contribution of these endocrine factors to any observed alterations. Circadian disruption resulted in pronounced deficits in learning and memory paralleled by marked reductions in hippocampal cell proliferation and neurogenesis. Significantly, deficits in hippocampal-dependent learning and memory were not only seen during the period of the circadian disruption, but also persisted well after the cessation of jet lag, suggesting long-lasting negative consequences on brain function.Conclusions/SignificanceTogether, these findings support the view that circadian disruptions suppress hippocampal neurogenesis via a glucocorticoid-independent mechanism, imposing pronounced and persistent impairments on learning and memory.

Work Life Balance up in the Air – Does Gender Make a Difference between Female and Male International Business Travelers?

“…Recent neuroscience studies conducted with female hamsters (but believed to be applicable to human beings as well) show that regular change of rhythm leads to tiredness and forgetfulness in the short-run and to concentration disturbances in the long-run. Even negative impact on the brain could be observed (Gibson, Wang, Tjho, Khattar, & Kriegsfeld, 2010).…”

Day differences in the cortisol awakening response predict day differences in synaptic plasticity in the brain

“…For example animal studies indicate that healthy circadian glucocorticoid oscillations boost learning-dependent synaptic formation and maintenance (Liston et al, 2013). It is clear that disrupted circadian patterns (not just sustained high levels) of glucocorticoid secretion are associated with cognitive deficits (Cho et al, 2000;Gibson et al, 2010;Evans et al, 2011) as well as a wide range of neuropsychiatric diseases (Wulff et al, 2010;Menet and Rosbash, 2011;Jagannath et al, 2013).…”

Synchrony and desynchrony in circadian clocks: impacts on learning and memory

“…Moreover, these cognitive decrements were accompanied by higher cortisol levels and temporal lobe atrophy (Cho 2001). Experimental jet-lag conditions in hamsters also resulted in persistent long-term cognitive deficits in spatial memory accompanied by significant decreases in cell proliferation and hippocampal neurogenesis (Gibson et al 2010). The severity of neurogenesis deficits are direction dependent with phase advances resulting in greater suppression of hippocampal neurogenesis (Kott et al 2012).…”

“…Furthermore, disruption of glucocorticoid cycling following learning by increasing trough glucocorticoid levels reduces survival of learning-induced spines and impairs long-term memory (Liston et al 2013). Prolonged increases in glucocorticoid levels mediate, at least in part, the effects of chronic jet lag on decreased neurogenesis in rodent models (Gibson et al 2010) and temporal lobe atrophy in humans (Cho 2001). Chronic exposure to high levels of glucocorticoids disrupts previous memories and eliminates new spines induced by learning as well as previously present spines (Liston et al 2013).…”