Cash-Padgett, T. V. | bioRxiv Science

bioRxiv2021

Differential encoding of safe and risky offers

Common currency theories in neuroeconomics hold that neurons in specific brain regions specifically encode subjective values of offers and not stimulus-specific information. The rationale behind these theories is that abstract value encoding lets the decision maker compare qualitatively different options. Alternatively, expectancy-based theories hold that the brain preferentially tracks the relationship between options and their outcomes, and thus does not abstract away details of offers. To adjudicate between these theories, we examined responses of neurons in six reward regions to risky and safe offers while macaques performed a gambling task. In all regions, responses to safe options are unrelated to responses evoked by equally preferred risky options. Nor does any region appear to contain a specialized subset of value-selective neurons. Finally, in all regions, responses to risky and safe options occupy distinct response subspaces, indicating that the organizational framework for encoding risky and safe offers is different. Together, these results argue against the idea that putative reward regions carry abstract value signals, and instead support the idea that these regions carry information that links specific options to their outcomes in support of a broader cognitive map.

neuroscience↗

bioRxiv2020

A functional hierarchy for choice in medial prefrontal cortex

Hierarchical approaches to functional neuroanatomy propose that choice-relevant brain regions have overlapping functions and can be organized into a series that progressively transforms information about options into choices. Here, we examined responses of neurons in four regions of the medial prefrontal cortex as macaques performed two-option risky choices. All four regions encoded economic variables in similar proportions and showed putative signatures of key choice-related computations. We found evidence for a hierarchical organization proceeding from areas 14[->]25[->]32[->]24. Specifically, we found that decodability of eight distinct task variables increased along that path, consistent with the idea that hierarchically later regions make these variables more separable. We also found longer intrinsic timescales in the same series, further supporting the idea of a hierarchy. Together these results highlight the importance of the medial wall in choice, endorse a specific hierarchical organization, and argue against a modular functional neuroanatomy of choice.

neuroscience↗