Menstrual cycle phase modulates reward sensitivity and performance monitoring in young women: Preliminary fMRI evidence.

The ability to learn from errors or the positive outcomes of one's actions has been connected to a differential functionality of the mesolimbic dopamine system. Variations in dopaminergic transmission and D2-receptor (DRD2) density in the striatum may thereby incline the individual to be either more reward- or punishment-sensitive. The steroid hormones estradiol (E2) and progesterone (PROG) are known to modulate dopaminergic tone. While E2 may enhance dopaminergic release and reduces DRD2, PROG may oppose these effects and attenuates dopaminergic responses. In women, marked changes in the concentration of these hormones occur across the menstrual cycle. Hence, the aim of this study was to assess whether reinforcement learning is modulated by menstrual cycle phase. Fifteen female subjects underwent fMRI while performing a probabilistic feedback learning task twice during their menstrual cycle--once in a phase dominated by E2 (late follicular phase), and a second time in the presence of high PROG (mid luteal phase).The goal of the learning task was to select the more frequently rewarded symbols from 3 symbol pairs, which was enforced by probabilistic feedback. A behavioral post-test examined learning performance and the tendency towards reward or punishment sensitivity (i.e., preference to choose the most often rewarded symbol 'A' or to avoid the least often rewarded symbol 'B', respectively). We found that individual reward sensitivity was enhanced in the follicular relative to the luteal phase, while the ability to learn from negative feedback was compromised. In contrast, during the luteal phase this behavior was reversed and women showed an enhanced punishment learning bias. On the neural level, activation of the dorsal anterior cingulate cortex and adjacent rostral cingulate zone (dACC/RCZ) was decreased when subjects received negative feedback in the follicular relative to the luteal phase. Additionally, in the luteal phase an enhanced ability to learn from negative feedback was accompanied by a stronger signal in the dACC/RCZ in response to negative feedback. These findings provide initial evidence for intra-individual differences in reward and punishment sensitivity due to naturally occurring hormonal changes across the menstrual cycle.