The Neural Correlates of Individual Differences in Reinforcement Learning during Pain Avoidance and Reward Seeking

Abstract

Organisms learn to gain reward and avoid punishment through action-outcome associations. Reinforcement learning (RL) offers a critical framework to understand individual differences in this associative learning by assessing learning rate, action bias, Pavlovian factor (i.e., the extent to which action values are influenced by stimulus values), and subjective impact of outcomes (i.e., motivation to seek reward and avoid punishment). Nevertheless, how these individual-level metrics are represented in the brain remains unclear. The current study leveraged fMRI in healthy humans and a probabilistic learning go/nogo task to characterize the neural correlates involved in learning to seek reward and avoid pain. Behaviorally, participants showed higher learning rate during pain avoidance relative to reward seeking. Additionally, subjective impact of outcomes was greater for reward trials and associated with lower response randomness. Our imaging findings showed that individual differences in learning rate and performance accuracy during avoidance learning were positively associated with activities of the dorsal anterior cingulate cortex (ACC), mid-cingulate cortex, and postcentral gyrus. In contrast, the Pavlovian factor, a measure of the extent to which action values are influenced by stimulus values, was represented in the precentral gyrus and superior frontal gyrus during pain avoidance and reward seeking, respectively. Individual variation of subjective impact of outcomes was positively predicted by activation of the left posterior cingulate cortex. Finally, action bias was represented by the supplementary motor area (SMA) and pre-SMA whereas the superior frontal gyrus played a role in restraining this action tendency. Together, these findings highlight for the first time the neural substrates of individual differences in the computational processes during RL.Significant StatementLearning how to gain reward and avoid punishment is critical for survival. Reinforcement learning models offer several measures characterizing such learning including learning rate, action bias, Pavlovian factor, and subjective impact of outcomes. Yet, the brain substrates subserving individual differences of these metrics remain unclear. The current study identified the distinct involvement of the anterior, mid, and posterior cingulate cortex, along with the supplementary motor area and superior frontal gyrus in representing distinct learning metrics that influence how individuals learned to initiate or inhibit an action to gain reward and avoid painful outcomes. Our findings help delineate the neural processes which may shed light on action choices, future behavior prediction, and the pathology of mental illnesses that implicate learning dysfunctions.

Reinforcement feedback impairs locomotor adaptation and retention

“…Previous research has demonstrated behavioral individual differences in reinforcement learning paradigms ( Grunitzki et al, 2014 ; Aberg et al, 2016 ). Moreover, differences in neurophysiological responses have also been noted between reinforcement and non-reinforcement learners ( Smillie et al, 2011 ; Kaiser et al, 2018 ; Le et al, 2024 ). In the case of this study, reinforcement learners (i.e., those who maintain their performance) may have a greater overall ability to integrate the abstracted numerical feedback and may utilize different neural mechanisms to modify motor behavior, thus resulting in better retention compared to others within their group.…”