# Computational signatures of uncertainty are reflected in motor cortex excitatory neurochemistry

## TL;DR

This study shows how the brain's motor cortex uses excitatory signals to update beliefs and adapt in uncertain situations.

## Contribution

The study identifies motor cortex glutamate+glutamine as a neural marker of individual differences in uncertainty processing.

## Key findings

- Region-specific relationships exist between motor cortex glutamate+glutamine and prediction errors and volatility beliefs.
- High trait anxiety is linked to faster post-reversal responses in a sensorimotor learning task.
- Dynamic belief updating is observed in response to environmental changes using a computational model.

## Abstract

How individuals process and respond to uncertainty has important implications for cognition and mental health. Here, we use computational phenotyping to examine inter-individual differences in uncertainty processing in relation to neurometabolites and trait anxiety in humans. We introduce a categorical state-transition extension of the Hierarchical Gaussian Filter to model individuals’ evolving beliefs about transition probabilities in a four-choice probabilistic sensorimotor learning task with a reversal. Using 7-Tesla Magnetic Resonance Spectroscopy, we measure neurotransmitter levels in the primary motor cortex. Model-based results reveal dynamic belief updating in response to environmental changes. We further find region-specific relationships between baseline primary motor cortex glutamate+ glutamine levels and prediction errors and volatility beliefs. High trait anxiety is associated with faster post-reversal responses. This study establishes a direct neurochemical correlate of hierarchical belief updating, identifying motor cortex glutamate + glutamine as an important neural marker of inter-individual differences in uncertainty processing.

Using computational modelling and neurochemical analysis, this study shows how motor cortex excitatory signals guide belief updating and adaptive learning in uncertain environments.