New research highlights potential role of the thalamus in complex reasoning

By recording neural activity of the prefrontal cortex, the part of the brain that drives executive functions such as making complex decisions, and the thalamus, which is classically considered a relay, researchers provide an updated view of the thalamus in complex reasoning. In a November 13 Nature paper, researchers at Tufts University School of Medicine studied these circuits in tree shrews. These animals can arbitrate between errors due to their own perceptual misjudgments versus those that are truly due to environmental shifts. The scientists found that the thalamus is critical for this process. By keeping track of the different sources of uncertainty (perceptual vs. environmental), the thalamus allows the animal to appropriately shift its behavior in a manner that better matched true environmental changes.

Abstract: Making adaptive decisions in complex environments requires appropriately identifying sources of error. The frontal cortex is critical for adaptive decisions, but its neurons show mixed selectivity to task features and their uncertainty estimates, raising the question of how errors are attributed to their most likely causes. Here, by recording neural responses from tree shrews (Tupaia belangeri) performing a hierarchical decision task with rule reversals, we find that the mediodorsal thalamus independently represents cueing and rule uncertainty. This enables the relevant thalamic population to drive prefrontal reconfiguration following a reversal by appropriately attributing errors to an environmental change. Mechanistic dissection of behavioural switching revealed a transthalamic pathway for cingulate cortical error monitoring to reconfigure prefrontal executive control. Overall, our work highlights a potential role for the thalamus in demixing cortical signals while providing a lowdimensional pathway for cortico-cortical communication.

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