Internal perturbation reveals the flexible and adaptive nature of the coordination between decisions and movements
Although growing evidence indicates that decision-making and movement control are tightly coordinated, the functional significance of this coordination remains poorly understood. In particular, it is unclear whether changes in the animals arousal are sufficient to reorganize decision-action coordination in a manner that preserves behavioral efficiency. To address this question, we pharmacologically slowed behavior in rhesus monkeys performing a reaching-based foraging task while leaving task demands unchanged. Under this internal perturbation, prolonged decisions were initially associated with shorter movement durations, revealing a compensatory coordination that reduced the additional temporal cost of slower deliberation. As animals progressively adapted across sessions, decision durations decreased, reward rates increased, and compensatory coordination became less prevalent, giving way to patterns of decision-movement co-regulation. This observation suggests that compensatory adjustments are recruited transiently during adaptation rather than representing a constitutive mode of behavioral control. These findings provide causal evidence that an internally-induced slowing of decision-making is sufficient to reorganize the temporal relationship between decisions and movements. More broadly, they support the view that decision-making and movement execution are regulated as complementary components of a unified adaptive control process that flexibly adjusts the temporal organization of behavior in response to changes in internal state, thereby contributing to the maintenance of efficient reward acquisition.