Increased Emotional Instability After Sleep Deprivation:A Functional Brain Network Study

As a consequence of modern life styles and occupations, many people experience fewer hours of sleep or even sleep loss. Sleep deprivation (SD) has negative impact on both individual health and social stability. Studies showed that SD can result in multiple cognitive deficits, including attention, memory, executive function and emotion, etc. Altered neural activities were widely distributed across the whole brain, especially the prefrontal cortex and some sub-cortical areas such as thalamus, hippocampus and amygdala. What’s more, large individual differences were reported in cognitive responses to SD, suggesting a trait-like differential vulnerability.Based on the existed researches, we have learned that SD lead to variety cognitive impairments. However, despite substantial researches focusing on the interaction between sleep and cognition, especially memory, the impact of SD on affective and emotional regulation is remained to be explored. Nearly all psychiatric and neurological mood disorders express co-occurring abnormalities of sleep, suggesting an intimate relationship between sleep and emotion. In order to study on the influence of SD to emotion function and its neural basis, we performed a task-fMRI. In this study, we asked participants to take two session tests, one after normal sleep, one after SD. During each test, participants viewed and rated the subjective emotional intensity of150standardized affective pictures on a1-5scale, corresponding to increasing intensity. We found that the positive affect of subjects were significantly decreased, and the activation regions during viewing pictures were altered. After SD, the activation of Middle Frontal Gyrus, Insula, Postcentral Gyrus, Superior Temporal Gyrus, Middle Temporal Gyrus, Middle Occipital Gyrus and some area in cerebellum were increased when viewing affective pictures, while midbrain was less activating. The additional activation of high order regions may be a compensatory response to SD, but the function of midbrain may be impaired. Besides, the activation is different when viewing different valence affective pictures. During viewing negative pictures, the activation of Posterior Cingulate and Middle Occipital Gyrus were increased, and no aberrant activation was found when viewing positive pictures. It may suggest that the emotional process of different valence pictures may be separated after SD.Resting-state fMRI are obtained in a task-free condition, which is characterized by the significant low frequency spontaneous fluctuation, reflect the "baseline" brain activities. Most studies are focused on cognitive deficits after SD, it remains unclear how the resting-state brain activity can be impacted by SD. And, the altered neural activities were spread across whole brain. So I wonder if the basic information processing efficiency of brain is changed after SD, and the cognitive performance deficits, especially emotion process were related to this efficiency change. In the second study, we investigated the topological properties of the human brain networks of healthy subjects under sufficient sleep and sleep deprived conditions. The negative correlation was less-suppressed in SD condition, suggesting a deceased inhibition. After sufficient sleep, the brain networks showed the property of small-worldness. Compared with the resting state under sufficient sleep, the small-world property was significantly enhanced after SD condition, suggesting a possible compensatory adaptation of the human brain. And the less-advanced network as the occipital network and sensorimotor network were more sensitive to SD, while the higher order networks were less changed. The aberrant regions conform to the finding in task fMRI, which may be related to the cognitive deficits after SD. Specifically, the altered measurements are correlated with the neuroticism of subjects, indicating individuals with low-levels of neuroticism are more resilient to SD. The results may provide us a better understanding of the emotion-sleep interaction and the individual differences.In order to explore the impact of SD to the emotional instability, we performed two studies from both sides of task-fMRI and resting-state fMRI. As described by the existed studies, our findings confirmed the phenomenon of increased emotional instability after SD. And the effect is not only related to the emotional task processing ability impairment in the SD condition, the altered resting-state activity may also work at the same time.