Hyperthymic temperament predicts neural responsiveness for monetary reward.

Background: Hyperthymic temperament is cheerful action orientation, and is suggested to have a protective effect on depressive symptoms. Responsiveness for reward, which is diminished in depressive patients, is suggested to be related to hyperthymic temperament. Moreover, neural hypoactivation in the reward system in depressive patients is well known. However, only a few previous studies have investigated the neurobiological substrate of hyperthymic temperament. We investigated the relationship between hyperthymic temperament and responsiveness to monetary rewards at the neural level.

Methods: Healthy participants performed a modified version of the monetary incentive delay task in a functional magnetic resonance imaging scanner. We explored the brain regions where neural responsiveness for monetary reward was predicted by hyperthymic temperament.

Results: Brain areas in the reward system were widely activated for reward anticipation. Activation in the left thalamus and left putamen was positively predicted by hyperthymic temperament. Conversely, activation in the ventral striatum and right insula was not modulated by hyperthymic temperament. No region activated for reward outcome was not modulated by hyperthymic temperament.

Limitations: Behavioral responsiveness to reward was not predicted by hyperthymic temperament or neural activity. Moreover, we did not correct P values for multiple regression analysis, considering that this was an exploratory study.

Conclusions: We found a neurobiological foundation for the protective aspect of hyperthymic temperament against depression in the reward system. Our findings suggest that the hyperthymic temperament may modulate attentional or motor responses or optimal selection of behavior based on reward, rather than value representation.