Resilience, the ability to overcome stressful conditions, is found in most mammals and varies significantly among individuals. A lack of resilience can lead to the development of neuropsychiatric and sleep disorders, often within the same individual. Despite extensive research into the brain mechanisms causing maladaptive behavioral-responses to stress, it is not clear why some individuals exhibit resilience. To examine if sleep has a determinative role in maladaptive behavioral-response to social stress, we investigated individual variations in resilience using a social-defeat model for male mice. Our results reveal a direct, causal relationship between sleep amount and resilience-demonstrating that sleep increases after social-defeat stress only occur in resilient mice. Further, we found that within the prefrontal cortex, a regulator of maladaptive responses to stress, pre-existing differences in sleep regulation predict resilience. Overall, these results demonstrate that increased NREM sleep, mediated cortically, is an active response to social-defeat stress that plays a determinative role in promoting resilience. They also show that differences in resilience are strongly correlated with inter-individual variability in sleep regulation.

Resilience, the ability to overcome stressful conditions, is found in most mammals and varies significantly among individuals. A lack of resilience can lead to the development of neuropsychiatric and sleep disorders, often within the same individual. Despite extensive research into the brain mechanisms causing maladaptive behavioral-responses to stress, it is not clear why some individuals exhibit resilience. To examine if sleep has a determinative role in maladaptive behavioral-response to social stress, we investigated individual variations in resilience using a social-defeat model for male mice. Our results reveal a direct, causal relationship between sleep amount and resilience—demonstrating that sleep increases after social-defeat stress only occur in resilient mice. Further, we found that within the prefrontal cortex, a regulator of maladaptive responses to stress, pre-existing differences in sleep regulation predict resilience. Overall, these results demonstrate that increased NREM sleep, mediated cortically, is an active response to social-defeat stress that is both necessary and sufficient for promoting resilience. They also show that differences in resilience are strongly correlated with inter-individual variability in sleep regulation.

Introduction:Stress can have a variety of detrimental effects on humans. From depression and anxiety to schizophrenia, stress plays a factor in the development of these diseases through neurochemical changes in the brain and elevated levels of hormones. Among the geriatric population, decreased sleep levels are known to be a frequent issue; insomnia rates among the senior population are much higher in frequency compared to any other age group. Sleep deprivation also leads to major consequences in the brain and sleep disruption is linked to neuropsychological illness; however, the specific mechanisms involved in these effects are not understood. This study focuses on the resilient effects of ΔFosB, a protein known to mediate resilience to stress and the direct effect of sleep deprivation on ΔFosB expression in areas known to mediate resilience to social stress. We hypothesize that ΔFosB may be part of the mechanism through which sleep alters resilience to social stress.Methods:Mice were sleep-deprived for an eight-hour period for five days. After sleep deprivation they were subject to social defeat and underwent avoidance testing. The brains of these mice were removed, and immunohistochemistry analysis was conducted to determine ∆FosB expression in various sections of the brain.Results:The preliminary findings of this study indicates that sleep is altered in resilient animals and that sleep deprivation may lead to increased resilience to social defeat. The most significant decrease in ∆FosB expression was found in the prelimbic cortex, a change associated with resilience, and which was observed after chronic sleep deprivation. Contrarily, there was also an increase of ∆FosB expression in the nucleus accumbens.Conclusion:These findings indicate that changes in ∆FosB activation in the brain is a significant factor for promoting resilient behavior in situations of social stress. In particular, a decrease in ∆FosB activation in the PLC plays a role in explaining how sleep deprivation contributes to decreased social resilience in situations of social stress.