# Rapid dopaminergic signatures in movement: Reach vigor reflects reward prediction error and learned expectation

## TL;DR

The study shows that how vigorously people move is influenced by their brain's reward prediction signals, linking motivation and movement in real time.

## Contribution

The paper demonstrates that human reach vigor dynamically tracks reward prediction error and learned expectation on rapid timescales.

## Key findings

- Peak velocity of reaching movements scales with the expected value of probabilistic rewards.
- Reach velocity changes transiently following feedback, reflecting the sign and magnitude of reward prediction error.
- Kinematic changes across trials align with dopaminergic learning signals and value updating.

## Abstract

Movements become more vigorous when rewards are expected, suggesting that motivational signals influence motor control. Dopaminergic neurons, known to encode reward expectation and prediction error, are prime candidates for linking value and vigor. Here, we show that human reach vigor dynamically tracks canonical dopaminergic learning signals not only at movement onset but also during ongoing motion. Using a reaching task with probabilistic rewards (0, 33, 66, and 100%), we observed that peak velocity scaled with expected value. Crucially, following feedback, reach velocity was transiently invigorated or enervated in proportion to the sign and magnitude of the reward prediction error. Trial-by-trial changes in kinematics reflected value updating, consistent with dopaminergic phasic learning signals. These results demonstrate that movement vigor is modulated by reward-learning signals on rapid timescales, revealing a real-time behavioral readout of motivational computation in the brain.

Movement vigor rapidly tracks neural signatures of reward prediction error.