Functional Magnetic Resonance Imaging Research On Effect Of Acute Stress On Cognitive Functions In The Brain

Stress is defined as an effect of interactions between the organism and environment,and a comprehensive response of breaking the homeostasis by the stimulus and out of human control.The working environment during military flights is characterized by high risk,complexity and uncertainty,and often induces a state of psychological and physiological stress among pilots.In the new era of this military revolution,how to maintain the pilots' normal cognitive abilities in case of unexpected danger has become an important subject of military psychology.This study is sponsored by the Twelfth and Thirteenth Five-year Plan in the military,and intended to build acute stress models in the laboratory to reveal the characteristics and mechanisms of cognitive alteration caused by acute stress.This work will contribute to improving the selection and training level of military pilots.MethodsThirty-five healthy male participants were recruited in this experiment with a self-controlled design.Using functional magnetic resonance imaging(fMRI)with regional homogeneity,seed-based functional connectivity analysis,general linear models,psychophysiological interactions and multiple regression analysis,we investigated the effects of acute stress on variable patterns of the brain activation involved in the brain's spontaneous activity,resting-state amygdala network,working memory,and risk decision-making.Results1.Effects of acute stress on spontaneous activity of the brainRegional homogeneity(ReHo)was used to study how acute stress impacted the spontaneous activity of the brain.We found(1)increased ReHo was located in the middle temporal gyrus,supramarginal gyrus,precuneus,and inferior parietal lobule under acute stress;(2)decreased ReHo was located in the orbital frontal cortex,supplementary motor cortex,and postcentral gyrus under acute stress;(3)the decreased ReHo in the left orbital frontal cortex was significantly correlated with the individual extraversion scores.2.Effects of acute stress on resting-state amygdala networkSeed-based functional connectivity analysis was used to investigate how acute stress impacted the resting-state amygdala network of the brain.We took basolateral amygdala(BLA),centromedial amygdala(CMA),and superficial amygdala(SFA)as the seed for functional connectivity analysis.We found(1)acute stress had distinct impact on the functional connectivity pattern of the BLA and CMA subregions;(2)increased BLA functional connectivity with the posterior cingulate cortex/retrosplenial and increased CMA functional connectivity with the medial prefrontal cortex under acute stress;(3)neuroticism was positively correlated with altered functional coupling of the BLA with the anterior insular cortex,dorsal anterior cingulate cortex,and pregenual anterior cingulate cortex.3.Effects of acute stress on working memoryNumerical n-back was used to study the neural mechanism underlying how acute stress that impacts working memory.A general linear model and psycho-physiological interaction model were used in the present analysis.We found(1)less deactivation in the posterior cingulate cortex under acute stress;(2)acute stress resulted in significantly reduced dorsolateral prefrontal cortex(DLPFC)connectivity with the precuneus and precentral gyrus;(3)reduced DLPFC connectivity with the precentral gyrus was significantly correlated with the increased reaction time under acute stress.4.Effects of acute stress on risk decision-makingBalloon analogue risk task(BART)was used to study the neural mechanism underlying how acute stress impacted risk decision-making.A general linear model and multiple regression model were used in the present analysis.We found:(1)a positive correlation between neuroticism and greater risk-taking behaviour under acute stress;(2)higher trait neuroticism levels predicted an increased activation of risk modulation in the dorsal anterior cingulate cortex during risk-taking,and predicted a decreased activation of risk modulation in the DLPFC during cash-out under acute stress;(3)positive correlations between neuroticism and increased activation within the parietal cortex were found during cash-out or after explosion,without consideration of the escalation of the risk level.ConclusionsIn summary,our study indicated the effects of acute stress on variable patterns of the brain involved in spontaneous activity,resting-state amygdala network,working memory and risk decision-making,and found a relationship between personality traits and stress-induced alterations of cognitive performance and functional brain networks.These results can shed light on the neural mechanism by which acute stress influences the cognitive function and improves the selection and training level of military pilots.