Abstract
Issuing a goal-directed action requires specifying the goal of the action as well as planning the hand trajectory to obtain it. Accumulating results suggest that planning a straight point-to-point trajectory is more efficient and likely to involve simpler optimization process compared to the planning of trajectories with more complex shapes (e.g., curved trajectories). We sought to find evidence for the qualitative difference between the two planning modes through the investigation of reaction times (RT) in a pointing task performed with the wrist. In experiment 1, 18 subjects performed delayed straight and curved via-point reaching movements to arrays of 2 or 8 targets. Both trajectory type and number of possible targets affected RT. In experiment 2 (N=14), we demonstrate a switching cost between the issuing of the two types of trajectories, irrespective of changes in target position. Unexpectedly, trajectory type did not affect RT in experiment 2, likely due to the lack of target pre-cuing in experiment 2. Our results suggest that the planning of curved and straight trajectories differ in their memory load during pre-planning and requires a time-consuming update of the motor commands when switching between straight and curved plans.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Declarations
Funding: This research was supported by the Helmsley Charitable Trust through the Agricultural, Biological and Cognitive (ABC) Robotics Initiative and by the Marcus Endowment Fund both at Ben-Gurion University of the Negev, by the United States-Israel Binational Science foundation grant 2015327, and by ISF grant 607/16 for Lior Shmuelof.
Conflicts of interest/Competing interests: Authors declare no conflict of interest.
Availability of data and material: Data will be available upon acceptance of the paper.
Code availability: Codes will be available upon acceptance of the paper.
Ethics approval: Study was approved by the institutional ethics committee.
Consent to participate: All participants signed a consent form.
Consent for publication: Authors read and approved the publication of the manuscript.