Sleep Deprivation Impairs Empathy For Pain And Related Brain Functions

Adequate sleep has a very important impact on people’s physical and mental health.Lack of sleep can lead to multiple adverse effects,both physically(e.g.obesity,heart health)and psychologically(e.g.depression,cognitive impairment).Therefore,it is very important to explore the physical and mental state of people who lack sleep.This can not only help us understand the direct consequences of sleep loss,but also help us to infer the neuronal mechanism behind sleep.Empathy for pain plays a protective role in survival and has an important impact on successful social interactions.Sleep loss is commonplace in today’s society,and people are increasingly troubled by it.Previous studies have investigated whether sleep loss can affect empathy for pain,but the results are uncertain.We aim to investigate whether there is such an effect and the dynamics of the time course and frequencies of neural activity involved in this effect by recording and analyzing EEG signals.We recruited 25 healthy adults(11 women)and asked them to perform pain judgments and unpleasant scores on the painful and neutral pictures presented after a night sleep or sleep deprivation,and record their neural activities.The results showed that the amplitude of the early components of empathy for pain processing(N2,N340)was significantly reduced after sleep deprivation.In further time-frequency analysis,under sleep deprivation conditions,the power in the θ2(5-7 Hz)frequency band is also reduced.Moreover,only under sleep deprivation conditions,the reduction of θ2 was positively correlated with the subjective scores of pain to others and self-unpleasantness.Our results indicate that sleep deprivation may weaken the sharing of emotions for empathy for pain to some extent.Considering that the observer’s own emotional state could also have an impact on empathy for pain,we conducted the second study-exploring the emotional changes caused by sleep deprivation,physically and psychologically.It is widely believed that sleep deprivation has a negative impact on emotions and emotional processing.Therefore,in the second study,we focused on emotions in the resting state.The default network is a brain network that is highly active at rest,and previous studies have shown that the connection within the default network is damaged after sleep deprivation,and this damage is related to emotions.Dynamic research with high time resolution on the default network after sleep deprivation is rarely.Therefore,in Study2,we collected the resting state EEG data of night sleep and sleep deprivation from 31 subjects.ELORETA was used to reconstruct the electrical activity of the posterior cingulate gyrus(PCC)and the anterior medial prefrontal cortex(a MPFC),and the power envelope correlation was used to calculate the functional connection strength between PCC-a MPFC.The results showed that compared with one night sleep,the energy of PCC in the α band and the functional connection strength of PCC-a MPFC were significantly reduced after sleep deprivation.Interestingly,the damaged PCCa MPFC circuit is positively correlated with reduced positive emotions,which suggests that the default network plays a key role in subjective emotional states.Our moderating effect analysis further reveals that the strength of the interaction between anterior and posterior default network reduces the damage of sleep loss and brings positive emotions.Overall,the results show that there is a strong relationship between decoupling of the default network and feeling down of mood.Our research may help to better understand the emotional and cognitive processes after sleep loss.In general,this study clarified that sleep deprivation affects empathy for pain mainly through individual emotional processing,indicating that sleep deprivation has a certain destructive effect on pro-social behavior.Secondly,considering individual emotional states can affect empathy for pain,we explored individual mood changes after sleep deprivation and the neural mechanisms behind them,and for the first time introduced frequency changes and combined them with the functional connections between specific brain regions.It can be said that this research fills the gaps in related researches to a certain extent,and helps to better understand a series of physiological and psychological changes that occur after sleep deprivation.Finally,this research also proposed reflections and limitations,and on this basis,prospecting for future research directions.