Deep sleep brain activity helps mice resist social stress

Most adult sleep is non-rapid eye movement (REM), which is restorative and promotes resilience to stressful conditions. However, the brain mechanisms for non-REM sleep's relationship to stress resilience remain unclear. New in JNeurosci, Christopher Ehlen, from Morehouse School of Medicine, and colleagues explored how cortical brain activity in mice during non-REM influences behavioral responses to stressful social situations. The researchers specifically looked at activity in the prelimbic cortex, a brain region that puts emotional responses in context. There was suppressed activity in the prelimbic cortex, a defining feature of sleep, that predicted how resilient mice were to stressful experiences. More specifically, this silencing of neurons occurred during "slow-wave activity," or deep sleep. Following stressful experiences, these mice also experienced a reorganization of neural activity; the speed of neuron activity was redistributed in the prelimbic cortex. Says Ehlen, "The quality of sleep seems to be dictating how the prelimbic cortex is suppressing emotional responses, which we think is represented as neural firing rate. Our assumption is that animals susceptible to stress aren't sleeping as deeply and that there is an active response to stress that is intact in resilient animals because of their deep sleep." The researchers plan to explore whether depriving stress resilient mice of sleep alters neural activity in the prelimbic cortex. They also hope this work will inform human studies seeking neurobiological markers for stress resilience or susceptibility.