Why Movement Vigour Doesn’t Depend on Subsecond Fluctuations
Dr. Nicolas Tritsch, researcher at the Douglas Research Centre and Assistant Professor at McGill University’s Department of Psychiatry, and his team have just published an article investigating how dopamine levels in the striatum control movements. The article, entitled “Subsecond dopamine fluctuations do not specify the vigour of ongoing actions,” was published on November 10 in Nature Neuroscience.
Takeaways
This article shows that subsecond dopamine (DA) transients in the striatum are neither necessary nor sufficient to determine the vigour of ongoing limb movements. Instead, the overall dopamine tone plays a critical role in restoring movement vigour, particularly in Parkinsonian models. Attempts to manipulate dopamine levels transiently during movement using optogenetic techniques did not alter movement vigour. These results suggest that dopamine’s influence on motor control is more closely tied to motivation and action initiation rather than moment-to-moment modulation of movement speed or amplitude.
Why This Matters
This research challenges the long-standing assumption that phasic dopamine signals dynamically control movement vigour. The findings have significant implications for Parkinson’s disease treatment, showing that levodopa’s effectiveness does not depend on restoring rapid dopamine fluctuations. Consequently, therapeutic strategies should prioritize maintaining adequate dopamine tone rather than attempting to replicate natural phasic patterns.
Methodology
To investigate these mechanisms, Tritsch’s team trained head-fixed mice to perform self-paced, ballistic lever presses for water rewards. Dopamine dynamics in the dorsolateral and dorsomedial striatum were monitored using fiber photometry with GRAB-DA sensors during movement. The team induced unilateral dopamine neuron lesions and assessed the effect of levodopa treatment. Additionally, optogenetic tools were employed to inhibit (GtACR2) or stimulate (ChR2) midbrain dopamine neurons during ongoing movements to probe causal effects.
Results
The study revealed that vigourous lever presses require contralateral dopamine integrity but not subsecond dopamine transients. Dopamine levels in the dorsolateral striatum often dipped slightly, while levels in the dorsomedial striatum showed slight increases at movement onset; however, these fluctuations exhibited weak or no correlation with movement vigour. Importantly, levodopa restored movement vigour without reinstating phasic dopamine signals, and optogenetic manipulations failed to alter vigour even when dopamine levels were strongly modulated.
Interpretation
These findings indicate that dopamine does not function as an “online gain controller” for motor commands on a subsecond timescale. Instead, dopamine likely influences movement through longer-term mechanisms such as motivation, action selection, and reinforcement learning. While phasic dopamine signals may contribute to shaping motor patterns via synaptic plasticity over repeated trials, they do not appear to modulate movement vigour moment-to-moment.
Future directions
Future research should explore how dopamine-driven plasticity interacts with cortical and striatal circuits to encode movement vigour during learning. Investigating whether supra-physiological dopamine changes or specific dopamine neuron subtypes can modulate vigour under different behavioural contexts will be crucial. Additionally, developing Parkinson’s therapies that optimize dopamine tone without relying on phasic restoration represents a promising direction.
About the study
Liu H, Melani R, Maltese M, Taniguchi J, Sankaramanchi A, Zeng R, Martin JR, Tritsch NX. Subsecond dopamine fluctuations do not specify the vigor of ongoing actions.Nat Neurosci. 2025 Nov 10. doi: 10.1038/s41593-025-02102-1. PMID: 41214177.