Independent planning of timing and sequencing for complex movements


The current studies examined the processes involved in response sequencing and timing initiation for complex, multiple-element movements. Participants performed three element key-press movements in simple and choice reaction time (RT) paradigms (Experiment 1), or a study time paradigm that allowed the participants to control the foreperiod delay, which is thought to reflect advance preparation duration (Experiment 2). Sequencing requirements were manipulated by using either one hand (low sequencing complexity) or two hands (high sequencing complexity) and timing was manipulated by using either an isochronous (low timing complexity) or non-isochronous (high timing complexity) pattern. Increasing sequencing complexity had little effect on simple RT but increased participant-controlled foreperiod delay (i.e., study time). Conversely, increasing timing complexity had no effect on foreperiod delay but increased simple RT. These results provide compelling evidence that in a simple RT paradigm, sequencing preparation is performed during the foreperiod while timing preparation is delayed until the RT interval. Furthermore, choice RT increased with sequencing complexity and was relatively unaffected by timing complexity, indicative of sequencing preparation occurring during the choice RT interval and timing preparation occurring on-line. Collectively, the data indicate a dissociation and independence of the preparation of response timing and sequencing for complex movements, which is discussed in relation to the potential neural structures involved.

Acknowledgments: Supported by the Natural Sciences and Engineering Research Council of Canada (NSERC).