abstract Eliana Vassena

Eliana Vassena (Department of Experimental Psychology, Ghent University)

The cost of victory : neural basis of cost evaluation in a reward task

Reward evaluation is encoded by dopaminergic activity in the brain (Schultz, 1998). However, for optimal learning and decision-making, the costs attached to the reward are to be considered as well. Lesion studies in animals confirm that costs, such as delay and effort, are taken into account (Rudebeck et al., 2006). fMRI experiments show that effort cost is integrated with reward (Croxson et al., 2009). Furthermore, they suggest that different areas selectively respond to different costs, though measured in a choice paradigm involving different tasks (Prevost et al., 2010). In fact, if and how multiple costs are integrated in a cost signal is still unclear.

The goal of this fMRI study was to test for a common cost evaluation signal for effort and delay, addressing both costs in the same task and avoiding decision-making confounds. A good candidate for the current hypothesis was dopaminergic activity in midbrain and brainstem nuclei, known to be crucial in value estimation and recently proved to play a role in cost evaluation. Interestingly, conjoint activation for the effortful and delayed condition involves two separate areas in the brainstem, corresponding to Ventral Tegmental Area, known to be crucial in value prediction (Bromberg-Martin et al., 2010) and Dorsal Raphe Nucleus, consistent with recent findings in animals and humans (Miyazaki et al., 2011, Tanaka et al., 2004), and with theories of serotonin and dopamine interactions in cost and reward coding (Daw et al., 2002). This result provides interesting evidence for a common cost signal in the human brain."