Abstract
Chronic stress facilitates the development and progression of multiple psychiatric disorders, including depression and addiction. The dysregulation of approach motivation has been proposed as a mechanism of chronic stress, but it is unclear how chronic stress is related to approach motivation. The current study sought to elucidate the relationship between chronic stress and resting-state electroencephalographic (EEG) measures of approach motivation. Sixty undergraduate students filled out the Perceived Stress Scale (PSS) and were recorded with resting-state EEG. Hierarchical regression analyses revealed significant quadratic (U-shaped) associations between mean-centered PSS scores and all three EEG measures: alpha frontal asymmetry (AFA) (β = 0.32, 95% CI [0.0001, 0.0018], p = 0.032), delta power (β = 0.33, 95% CI [0.0003, 0.0036], p = 0.021), and theta power (β = 0.31, 95% CI [0.0002, 0.0035], p = 0.030). All quadratic effects remained statistically significant after false discovery rate (FDR; Benjamini-Hochberg) correction (all adjusted ps < 0.05). These findings suggest that there is a nonlinear relationship between chronic stress and approach motivation, i.e. at both low and high chronic stress levels, resting-state activation of approach motivation is enhanced, whereas at moderate chronic stress levels, approach motivation is reduced, probably reflecting more efficient allocation and conservation of brain resources. More importantly, our findings demonstrate the necessity of examining the baseline neural state in addition to the task-evoked responses when assessing stress-related changes of approach motivation, thereby providing novel insights into the mechanisms of stress adaptation and their implications for psychological health.