When performing a long chain of actions in rapid sequence, future movements need to be planned concurrently with ongoing action. However, how far ahead we plan, and whether this ability improves with practice, is currently unknown. Here we designed an experiment in which healthy volunteers were asked to produce 14-item sequences of finger movements quickly and accurately in response to numerical stimuli. On every trial, participants were only shown a fixed number of stimuli ahead of the current keypress. The size of this viewing window varied between 1 (next digit revealed with pressing of current key) and 14 (full view of the sequence). Participants practiced the task for 5 days and their performance was continuously assessed on random sequences. Our results clearly indicate that participants used the available visual information to plan multiple actions into the future, but that the planning horizon was limited: receiving more information than 3 movements ahead did not result in faster sequence production. Over the course of practice, we found larger performance improvements for larger viewing windows. Additionally, we show that the improved planning was accompanied by an expansion of the planning horizon with practice. Together, these findings show that one important aspect of sequential motor skills is the ability of the motor system to exploit visual information for planning multiple responses into the future.
bioRxiv Subject Collection: Neuroscience