Neural Response to Reward and Loss Following Basic Combat Training.

Background: The brain's responsiveness to rewarding stimuli is essential for adaptive functioning while deficits in neural reward processing have been linked to the transdiagnostic symptom of anhedonia. Acute or prolonged stressors may negatively impact neural reward responses; however, few studies have examined if real-world naturalistic stressors prospectively predict reductions in brain responses to rewards.

Methods: This pre-registered analysis (https://osf.io/f6e8w) used data from the ARMOR study to assess whether exposure to basic combat training (BCT), a demanding and stress-inducing 10-week program, led to reductions in electrophysiological measures of reward response. One hundred sixteen military recruits completed a virtual gambling task while electroencephalogram (EEG) was recorded before and after BCT. Mean EEG activity in the time window of the Reward Positivity (RewP; 175 - 325ms post-feedback at FCz) was averaged separately for the gain and loss condition.

Results: We found that neural response to both gain and loss feedback in the time-window of the RewP significantly decreased from baseline following BCT (b = -0.67, p <.001), but the difference between conditions did not (b = 0.28, p = .23). Greater reports of BCT-related stressors predicted decreased neural response to gain, but not loss. Finally, baseline reward-related power in the delta-band frequency prospectively predicted less self-reported BCT-related stress.

Conclusions: These findings suggest that experiencing the stress of BCT is associated with reductions in neural processing of both reward and loss feedback. Further, those with greater reward-related delta oscillatory activity may perceive less negative impact of real-world stressors.