Our earlier preprint is now out in JN! Led by Jonathan Chien, a talented MS student in the lab, now a PhD student at UT Austin.
Jonathan showed that reward context dominates population representations in the ACC. Trial outcomes are then encoded in a context-dependent manner, but information about the motor response that achieved the outcome is represented orthogonally
https://www.jneurosci.org/content/early/2023/07/25/JNEUROSCI.0292-23.2023
Abstraction of reward context facilitates relative reward coding in neural populations of the macaque anterior cingulate cortex
The anterior cingulate cortex (ACC) is believed to be involved in many cognitive processes, including linking goals to actions and tracking decision-relevant contextual information. ACC neurons robustly encode expected outcomes, but how this relates to putative functions of ACC remains unknown. Here, we approach this question from the perspective of population codes by analyzing neural spiking data in the ventral and dorsal banks of the ACC in two male monkeys trained to perform a stimulus-motor mapping task to earn rewards or avoid losses. We found that neural populations favor a representational geometry that emphasizes the valence of potential outcomes, while also facilitating the independent, abstract representation of multiple task-relevant variables. Valence encoding persisted throughout the trial, and realized outcomes were primarily encoded in a relative sense, such that cue valence acted as a context for outcome encoding. This suggests that the population coding we observe could be a mechanism that allows feedback to be interpreted in a context-dependent manner. Together, our results point to a prominent role for ACC in context-setting and relative interpretation of outcomes, facilitated by abstract, or “untangled,” representations of task variables. Significance Statement The ability to interpret events in light of the current context is a critical facet of higher-order cognition. The ACC is suggested to be important for tracking contextual information, while alternate views hold that its function is more related to the motor system and linking goals to appropriate actions. We evaluated these possibilities by analyzing geometric properties of neural population activity in monkey ACC when contexts were determined by the valence of potential outcomes, and found that this information was represented as a dominant, abstract concept. Ensuing outcomes were then coded relative to these contexts, suggesting an important role for these representations in context-dependent evaluation. Such mechanisms may be critical for the abstract reasoning and generalization characteristic of biological intelligence.
Alicia Izquierdo, Ph.D.
CogCompNeuro
Christopher Summerfield
Chris Rodgers
Fred M Stoll
The Oatmeal
