Neural mechanism of intertemporal choice: from discounting future gains to future losses.

Intertemporal choice, the tradeoff among outcomes occurring at different points in time, involves not only benefit options but also those associated with cost. Previous neuroimaging studies have primarily focused on discounting future gains; thus the neural mechanism underlying discounting future losses remains unidentified. Using event-related functional magnetic resonance imaging, we comprehensively investigated the neural mechanism of temporal discounting using two decision-making tasks with a symmetric pattern of gains and losses. Our results revealed that the lateral prefrontal and posterior parietal areas were activated in discounting both future gains and future losses, but their activations were stronger when discounting losses. Moreover, we found that the insula, thalamus and dorsal striatum were more activated during intertemporal choices involving losses, suggesting that the enhanced sensitivity to losses may be driven by negative emotions. In addition, whereas the posterior cingulate cortex and medial prefrontal cortex were activated when the choices included immediate options, extra regions including the anterior cingulate cortex, insula and superior frontal gyrus were preferentially activated when the choices involved immediate losses. Taken together, our findings suggest that a fronto-parietal network supports the common discounting process, and more importantly, discounting future losses and gains occurs asymmetrically in the brain. We speculate that this may provide a neural basis for the phenomenon that future losses are discounted less steeply than future gains.