Background: Men and women show differences in sensitivity to reward and punishment, which may impact behavior in health and disease. However, the neural bases of these sex differences remain under-investigated. Here, by combining functional magnetic resonance imaging (fMRI) and a variant of the Monetary Incentive Delay Task (MIDT), we examined sex differences in the neural responses to wins and losses and how individual reward and punishment sensitivity modulates these regional activities.
Methods: Thirty-sex men and 27 women participated in the fMRI study. We assessed sensitivity to punishment (SP) and sensitivity to reward (SR) with the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ). In the MIDT, participants pressed a button to collect reward ($1, 1¢, or nil), with the reaction time window titrated across trials so participants achieved a success rate of approximately 67%. We processed the Imaging data with published routines and evaluated the results with a corrected threshold.
Results: Women showed higher SP score than men and men showed higher SR score than women. Men relative to women showed higher response to the receipt of dollar or cent reward in bilateral orbitofrontal and visual cortex. Men as compared to women also showed higher response to dollar loss in bilateral orbitofrontal cortex. Further, in whole-brain regressions, women relative to men demonstrated more significant modulation by SP in the neural responses to wins and larger wins, and the sex differences were confirmed by slope tests.
Conclusions: Together, men showed higher SR and neural sensitivity to both wins, large or small, and losses than women. Individual differences in SP were associated with diminished neural responses to wins and larger wins in women only. These findings highlight how men and women may differ in reward-related brain activations in the MIDT and add to the imaging literature of sex differences in cognitive and affective functions.
Keywords: Gender; Individual difference; MIDT; Punishment; Reward; fMRI.