SUMMARY
Deciding when to initiate action is essential to survival. Insights from movement disorders and pharmacological studies implicate the neurotransmitter dopamine as a regulator of movement timing, but the underlying neural mechanisms are not understood. Here we show dynamic dopaminergic signaling over seconds-long timescales controls movement timing in mice. Animals were trained to initiate licking after a self-timed interval following a start-timing cue. Surprisingly, dopaminergic signals ramped-up slowly between the start-timing cue and the self-timed movement, with the slope predicting the movement time on single trials. Steeply rising signals preceded early lick-initiation, whereas slowly rising signals preceded later initiation, reminiscent of a ramp-to-threshold process. Higher baseline activity also predicted earlier self-timed movements. Optogenetic activation of dopamine neurons during self-timing caused systematic early-shifting of movement initiation, whereas inhibition caused late-shifting. These results reveal a causal role for dynamic dopaminergic signaling unfolding over seconds in controlling the moment-by-moment decision of when to move.
Competing Interest Statement
J.A.A. is a co-founder of OptogeniX, which produces the tapered optical fibers used in some experiments.
Footnotes
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The paper has been reformatted with an extended introduction. The supplementary discussion has been reformatted as a stand-alone theory manuscript, and as such, it has been removed from this paper.