During economic decisions, offer value cells in orbitofrontal cortex (OFC) encode the values of offered goods. Furthermore, their tuning functions adapt to the range of values available in any given context. A fundamental and open question is whether range adaptation is behaviorally advantageous. Here we present a theory of optimal coding for economic decisions. We propose that the representation of offer values is optimal if it ensures maximal expected payoff. In this framework, we examine offer value cells in non-human primates. We show that their responses are quasi-linear even when optimal tuning functions are highly non-linear. Most importantly, we demonstrate that for linear tuning functions range adaptation maximizes the expected payoff. Thus value coding in OFC is functionally rigid (linear tuning) but parametrically plastic (range adaptation with optimal gain). Importantly, the benefit of range adaptation outweighs the cost of functional rigidity. While generally suboptimal, linear tuning may facilitate transitive choices.
Bibliographical noteFunding Information:
We thank Heide Schoknecht for help with animal training, Nicolas Brunel and Daniel Chicharro for helpful conversations, and Harold Burton, Arno Onken, and Stefano Panzeri for comments on earlier versions of the manuscript. This work was supported by the National Institutes of Health (grant numbers R01-DA032758 and R01-MH104494 to C.P.-S. and grant numbers T32-GM008151 and F31-MH107111 to K.E.C.) and by the National Science Foundation (grant SES-1357877 to A.R.). This work was partly conducted while C.P.-S. was a visiting fellow at the Italian Institute of Technology.