Disentangling neural representations of value and salience in the human brain

Significance The value and salience of predictive cues are important signals for regulating approach–avoidance behavior and attentional processing, respectively. However, the two signals often are confounded in studies of decision-making. Indeed, recent results suggest that neural signals in the primate posterior parietal cortex (PPC) which previously were thought to encode value actually reflect salience. This finding has created considerable uncertainty about previously identified value signals. Here we experimentally dissociate value and salience and use pattern-based functional MRI to demonstrate distinct encoding of both signals in the PPC, thereby reinforcing the earlier reports of value in the PPC. Moreover, we show that the orbitofrontal cortex encodes the predicted value of appetitive and aversive outcomes on a common neural scale. A large body of evidence has implicated the posterior parietal and orbitofrontal cortex in the processing of value. However, value correlates perfectly with salience when appetitive stimuli are investigated in isolation. Accordingly, considerable uncertainty has remained about the precise nature of the previously identified signals. In particular, recent evidence suggests that neurons in the primate parietal cortex signal salience instead of value. To investigate neural signatures of value and salience, here we apply multivariate (pattern-based) analyses to human functional MRI data acquired during a noninstrumental outcome-prediction task involving appetitive and aversive outcomes. Reaction time data indicated additive and independent effects of value and salience. Critically, we show that multivoxel ensemble activity in the posterior parietal cortex encodes predicted value and salience in superior and inferior compartments, respectively. These findings reinforce the earlier reports of parietal value signals and reconcile them with the recent salience report. Moreover, we find that multivoxel patterns in the orbitofrontal cortex correlate with value. Importantly, the patterns coding for the predicted value of appetitive and aversive outcomes are similar, indicating a common neural scale for appetite and aversive values in the orbitofrontal cortex. Thus orbitofrontal activity patterns satisfy a basic requirement for a neural value signal.