Spatiotemporal interactions between arm movements: Kinematics not dynamics


We have previously demonstrated that reaching latency is affected by the direction of a preceding arm movement; reaches in the same direction have greater latency than reaches in opposite directions (Cowper-Smith et al., 2013). Under constant loading conditions, the direction of reaching is directly related to the muscles activated to produce the movement; as such, it is unclear if the effect we observed is due to movement direction (kinematics) or to muscle recruitment (dynamics). In the present study, participants completed pairs of arm movements to the left or right of centre; randomly, direction was the same or different for each pair. The first movement was made with a rubber band on the wrist pulling to the left, right, or neither side, whereas the second was always made without the band. Latencies were greater for same direction compared to opposite direction movements, regardless of the direction of pull from the rubber band. This indicates that the interaction between arm movements occurs at the level of kinematics rather than dynamics, possibly arising from motor control centres encoding intended movement trajectory.

Acknowledgments: Funded by NSERC (Westwood).