A brain-wide, trial- and time-dependent deterministic drive for self-initiated action decisions

Deciding when to act in the absence of external cues is essential for exploration, learning and survival. Yet how the brain makes such decisions remains controversial, with current models favoring either deterministic or stochastic underpinnings. We performed large-scale, single-unit recordings across eight brain areas in mice self-initiating voluntary actions. We found that action timing is predictable from neural activity, up to several seconds before action initiation, across all eight brain areas. This predictive activity reflects a deterministic drive whose initial value and rate vary trial-by-trial, and whose rate accelerates within trials. While noise contributes to timing variability, the deterministic drive is sufficient to trigger action. Thus, self-initiated timing decisions arise from a variable, brain-wide deterministic drive, challenging models where noise is the primary driver.