Abstract
Adaptive decision-making uses information gained when exploring alternative options to decide whether to update the current choice strategy. Magnocellular mediodorsal thalamus (MDmc) supports adaptive decision-making, but its causal contribution is not well understood. Monkeys with excitotoxic MDmc damage were tested on probabilistic three-choice decision-making tasks. They could learn and track the changing values in object-reward associations, but they were severely impaired at updating choices after reversals in reward contingencies or when there were multiple options associated with reward. These deficits were not caused by perseveration or insensitivity to negative feedback though. Instead, monkeys with MDmc lesions exhibited an inability to use reward to promote choice repetition after switching to an alternative option due to a diminished influence of recent past choices and the last outcome to guide future behavior. Together, these data suggest MDmc allows for the rapid discovery and persistence with rewarding options, particularly in uncertain or changing environments.
Highlights
Making adaptive decisions in complex uncertain environments often necessitates sampling the available options to determine their associated values
The current study sought to determine the influence of MDmc when learning and tracking probabilistic reward associations in stochastic reward environments
In the first set of experiments assessing learning and decision-making on the varying reward schedules, we found that the integrity of the MDmc is critical to allow monkeys to update their behavior efficiently following a reversal in the identity of the highest value stimulus
Summary
Making adaptive decisions in complex uncertain environments often necessitates sampling the available options to determine their associated values. Converging evidence suggests that the integrity of orbital and medial parts of prefrontal cortex supports the ability to use feedback to allow rapid regulation of choice behavior and to shift from search to persist modes of responding (Hayden et al, 2011; Khamassi et al, 2013; Morrison et al, 2011; Walton et al, 2004; 2011). It is not yet clear how all the relevant information is efficiently integrated across these cortical networks for this to occur. Causal evidence from animal models indicates that MD provides a critical contribution in many reward-guided learning and decision-making tasks, those requiring
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