The Effect Of Reward Sensitivity On The Two Stages Of Stress Response And Its Psychological And Neural Mechanism

In modern society,people are faced with various stressful events every day.Effectively coping with these threats and challenges is essential to maintain good physical and mental health.The autonomic nervous system and hypothalamic pituitary adrenal(HPA)axis play an important role.Successful coping with stress include two stages: reaction and recovery.Stress reactivity of the stress system in the reaction stage is conducive to the individual being keenly aware of the threat stimulus and mobilizing physical functions and psychological resources to deal with it.After the withdrawal of stressors,the rapid recovery of physical and mental state to normal level under the effect of regulatory mechanism is also considered the core mechanism of stress resilience.Studies in the past decade from behavioral to neuroimaging levels have confirmed that the reward system promotes stress resilience by reducing excessive stress response and promoting the psychosomatic state to recover more quickly after stress.The latest research has found that having a robust reward function is an essential factor in stress resilience,which is reflected explicitly in the higher sensitivity of individuals to reward.However,as the core system of stress response,how reward sensitivity affects the response mode of individuals in the two stages of stress is not clear,and the psychological and neural mechanisms,as well as the long-term neurobiological path to form this effect,remain to be explored.The investigation of these problems can expand our understanding of the reward system’s role and mechanism in the stress resilience field,thus providing suggestions for cultivating individuals’ ability to recover from stress and providing new insights into the potential pathogenesis.Study 1 investigated the effect of reward sensitivity on stress response patterns.Study 1a induced the social psychological stress response of the participants through the Trier social stress task,measured the salivary cortisol,heart rate and heart rate variability of the participants at different stages of stress,and asked them to report the stress-related cognitive and emotional feelings.The results showed that individuals with high reward sensitivity showed a highly effective stress response mode of rapid activation and recovery of the stress system.Study 1b explored the psychological mechanism in this two-stage influence path and found that high reward sensitivity promoted stress recovery through positive coping and positive emotions after stress.Study 2 explored the neural mechanism of reward sensitivity influencing stress response mode from the perspective of neuroimaging by using functional magnetic resonance imaging(f MRI)technology and provided evidence of the neural basis for the psychological mechanism found in study 1.Study 2a induced the participants’ social and psychological stress reaction through the Scan STRESS task and scanned the brain neural activity of the participants during the stress task.The results showed that the stronger activation of the default mode network(DMN),salience network(SN),central executive network(CEN)and its core brain regions,including the ventromedial prefrontal cortex(vm PFC),forebrain island and putamen mediated the relationship between reward sensitivity and the decline rate of cortisol stress response.These brain regions represent positive coping,threat perception and regulation,and reward-approaching behavior.Study 2b explored the neural mechanism of reward sensitivity promoting stress recovery from the brain’s spontaneous neural activities of participants at rest after stress.The results showed that the less functional connection between vm PFC and the middle temporal gyrus(MTG),which were related to negative self-reference thinking,accelerated the decline of cortisol in the resting state after stress.This result supported positive emotions’ role in the stress recovery phase.Using multimodal neuroimaging technology,study 3 explored the regulatory factors between reward sensitivity and acute stress response patterns.Study 3a examined whether the brain neural activity of the participants in the resting state before stress could regulate the relationship between reward sensitivity and stress response.The results showed that in the group with stronger spontaneous nerve activity of MTG before stress,those with high reward sensitivity showed a more efficient HPA axis response mode with rapid increase and decrease of cortisol.Moreover,interestingly,when the DMN responsible for self-reference processing and its core brain region vm PFC,as well as the SN responsible for threat perception,are more activated in the resting state,high reward sensitivity will instead lead to individuals showing non-adaptive psychosomatic response patterns.This result also reveals that reward sensitivity is not conducive to stress resilience under certain conditions.After exploring the regulatory effect of the core brain region in Study 2 on the spontaneous neural activity in the resting state,Study 3b investigated the regulatory mechanism of its inherent structural attributes on reward sensitivity and stress response.The research results found that the stress resilience effect of reward sensitivity mainly works in individuals with smaller gray matter volumes of the brain regions,which implies that high reward sensitivity can alleviate the abnormal stress response of those with poor development in the core brain region.The first three studies found an efficient stress response mode of rapid activation and rapid decline of highly reward-sensitive people by inducing acute stress responses in the laboratory.They explored the psychological and neural mechanisms and influencing factors.Study 4 tried to verify this mode on the daily function of the stress system.Study 4a first investigated the relationship between reward sensitivity and daily rhythmic operation of HPA axis and found that the reward positivity wave(Rew P),which is more closely related to dopamine function,is related to higher concentration of awakening cortisol.In contrast,P3,more closely related to positive emotions,is related to faster decline of awakening cortisol.Studies 4b and 4c further explored whether and how reward sensitivity,as a relatively stable factor,can shape the function of the stress system through long-term neurobiological pathways.The results showed that reward sensitivity led to a faster decline rate of arousal cortisol through a larger putamen gray matter volume,which reflected that the development of reward brain region promotes the diurnal regulation of HPA axis..And therefore,the low daily cortisol accumulation of highly reward-sensitive people optimizes the functional connection between the hippocampus and the inferior frontal gyrus,the core network of stress regulation.The research results highlight the dynamic and multifaceted interaction between pertinent allostatic factors in the reward-resilience pathway.It also implies that it can profoundly promote people’ s stress coping and stress resilience by cultivating reward sensitivity.In general,this series of studies revealed the influence mode of reward sensitivity on stress response and explored the acute response mechanism and long-term plasticity mechanism.The research results expand the theoretical framework of academic circles on reward system promoting stress resilience and emphasize the core role of vm PFC and reward-related neural circuits in stress resilience.The current research uses a variety of physiological response indicators and multimodal neuroimaging technology to comprehensively and deeply explore vital issues in the field of reward and stress.And the current study provides important inspiration for future researchers to explore broader stress resilience factors and shape the neurobiological path of the stress system.