Disentangling neural representations of value and salience in the human brain

Abstract

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.reward | punishment | decision-making | attention | MVPA T he value of predictive cues can be used to guide approachavoidance behavior. Approach and avoidance responses are proportional to the appetitive (positive) and aversive (negative) value of the cues, respectively. On the other hand, based on empirical and theoretical considerations (1-3) the absolute value (i.e., the salience) of a cue determines the amount of attention that a stimulus captures to facilitate further processing. Hence, in contrast to value, salience increases not only with the magnitude of reward but also with the magnitude of punishment (4, 5).Electrophysiological recordings in animals suggest that value is encoded in the firing rates of posterior parietal and orbitofrontal neurons (6-18). A large body of evidence from human imaging studies also suggests signatures of appetitive value in these regions (19-36). However, value and salience are perfectly correlated when appetitive stimuli are investigated in isolation (37). That is, if a signal increases with increasing reward, we need to know how it behaves with increasing punishments to decide whether it is coding for value or salience. Specifically, if the signal decreases with increasing punishment, it truly reflects value. However, if the signal also increases with increasing punishment, it reflects salience (Fig. 1C). Thus, value signals identified using only appetitive (or only aversive) stimuli could be explained equally well in terms of value or salience.Indeed, neurons in the lateral intraparietal area (LIP), which have long been thought to signal ...

Does my brain want what my eyes like? – How food liking and choice influence spatio-temporal brain dynamics of food viewing

“…These findings are in line with previous literature reporting decreased response times to highly valued visual items (Kahnt et al, 2014). Given that in our study liked items were more often chosen by participants in general, this association is likely due to the inherent parallel assessment of "liking" and "wanting" aspects during preference building (Finlayson et al, 2008).…”

“…when non-food objects are viewed (Levy et al, 2011). However, the superior parietal cortex has also been reported to be involved in the abstract coding of stimulus values in order to mediate goal-directed behaviors and to maximize the outcome of choices taken (Kahnt et al, 2014), as well as to enable choices between several alternative options (Kable and Glimcher, 2009;McClure et al, 2007). Electrical neuroimaging results have shown its involvement in such operations within 200ms after visual cues are encountered whose values need to be coded in an abstract form in order to enable decisions between choice alternatives (Harris et al, 2011).…”

Discrete coding of stimulus value, reward expectation, and reward prediction error in the dorsal striatum

“…Their argument raises the possibility that striatal neurons showing probability-dependent activity may reflect the motivational salience but not the value of stimuli and outcomes. The behavioral task we used in this study, however, cannot dissociate value from motivational salience (Kahnt et al 2014). Therefore, we cannot rule out the possibility that some neurons recorded in this study code motivational salience rather than value.…”

Social discounting involves modulation of neural value signals by temporoparietal junction

“…Note that recent research on TPJ function suggests that it is not a monolithic structure that supports one single cognitive function, but is more likely to be composed of anatomically and functionally distinct subdivisions that may subserve different computational roles such as value, salience, and ToM (11,24,25,30,31). Although we cannot rule out that our subjects used ToM or other mechanisms to make their decisions, it is possible that we found no evidence in favor of the first, ToM-based hypothesis simply because we did not explicitly elicit ToM cognition.…”