Neural Signatures of Subjective Value and Confidence in Decisions with Different Physical Costs

Two fundamental goals of decision making are to select actions that maximize rewards while minimizing costs and to have strong confidence in the accuracy of a judgment. Neural signatures of these two forms of value: the subjective value (SV) of choice alternatives and the value of the judgment (confidence), have been observed in ventromedial prefrontal cortex (vmPFC). However, the relationship between these dual value signals and their relative time courses are unknown. Furthermore, there are often several ways that one can obtain a desired reward, each entailing its own costs. Previous research investigated the neural representations of many types of decision costs with the notable exclusion one evolutionarily significant expense: cardiovascular effort. It remains unclear how physical costs, such as pain and exertion are transformed into value information to guide decision making and the extent to which this process is domain-specific versus domain-general. To test this, in Experiments 1 and 2 we recorded fMRI while participants performed a two-phase ApAv task with mixed-outcomes of monetary rewards paired with significant physical costs. In Experiment 1 costs were painful shock stimuli, in Experiment 2 costs were intervals of demanding cardiovascular exercise on a stationary bike. Neural responses were measured during offer valuation (offer phase) and choice valuation (commit phase) and analyzed with respect to observed decision outcomes, model-estimated SV, confidence, and costs. During the offer phase, vmPFC tracked SV and decision outcomes, but it not confidence. During the commit phase, vmPFC tracked confidence, computed as the quadratic extension of SV, but it bore no significant relationship with the offer valuation itself, nor the decision. In fact, vmPFC responses from the commit phase were selective for confidence even for rejected offers, wherein confidence and SV were inversely related. Conversely, activation of the cognitive control network, including within lateral prefrontal cortex (lPFC) and dorsal anterior cingulate cortex (dACC) was associated with ambivalence, during both the offer and commit phases. None of these signals differed in magnitude between the pain and effort conditions, consistent with shared neural faculties of cost representations. However, inspection of voxel response patterns within those faculties revealed representational dissimilarity between the two types of decision costs, indicating that cost-domain-specific information is encoded throughout the decision making process. Within vmPFC in particular, the availability of cost-specific information over the course of a decision suggested qualitatively different decision processes under conditions of confidence and ambivalence. Taken together, our results reveal complementary representations in vmPFC during value-based decision making that temporally dissociate such that offer valuation (SV) emerges before decision valuation (confidence), both of which include specific information about costly consequences