The problem with value

Abstract

Neural correlates of value have been extensively reported in a diverse set of brain regions. However, in many cases it is difficult to determine whether a particular neural response pattern corresponds to a value-signal per se as opposed to an array of alternative non-value related processes, such as outcome-identity coding, informational coding, encoding of autonomic and skeletomotor consequences, alongside previously described "salience" or "attentional" effects. Here, I review a number of experimental manipulations that can be used to test for value, and I identify the challenges in ascertaining whether a particular neural response is or is not a value signal. Finally, I emphasize that some non-value related signals may be especially informative as a means of providing insight into the nature of the decision-making related computations that are being implemented in a particular brain region.

Keywords: Decision-making; Learning; Neuroeconomics; Reward.

Figure 1

Schematic of a simple experiment aimed at detecting neural responses to expectation of magnitude and probability of a juice outcome. Even if a cue is retrieving sensory features of the outcome (e.g. its sweetness, odor, texture or some combination thereof) but not its value, putative neural responses to the cue would still scale with both magnitude (the intensity of the sensory experience) and probability (the strength of the stimulus-stimulus association formed). Thus, distinguishing neural signals encoding cue-outcome associations that are entirely sensory based (i.e. cue → outcome sensory features) from cue-outcome associations that retrieve underlying values (cue → value(outcome)), is challenging using this type of manipulation.