Kinematic features of continuous hand reaching movements under simple and complex rhythmical constraints
Received 20 December 2009; received in revised form 21 February 2010; accepted 15 March 2010. published online 12 April 2010.
Abstract
Background
Auditory cues are known to alter movement kinematics in healthy people as well as in people with neurological conditions (e.g., Parkinson’s disease or stroke). Pacing movement to rhythmical constraints is known to change both the spatial and temporal features of movement. However, the effect of complexity of pacing on the spatial and temporal kinematic properties is still poorly understood. The current study investigated spatial and temporal aspects of movement (path and speed, respectively) and their integration while subjects followed simple isochronous or complex non-isochronous rhythmical constraints. Spatiotemporal decoupling was expected under the latter constraint.
Methods
Ten subjects performed point-to-point hand movements towards visual targets on the surface of a hemisphere, while following continuous auditory cues of different pace and meter. The spatial and temporal properties of movement were compared to geodesic paths and unimodal bell-shaped speed profiles, respectively. Multiple two-way RM-ANOVAs (pace [1–2Hz]×meter [duple–triple]) were performed on the different kinematic variables calculated to assess hand deviations from the model data (p⩽0.05).
Results
As expected, increasing pace resulted in straighter hand paths and smoother speed profiles. Meter, however, affected only the path (shorter and straighter under triple) without significantly changing speed. Such an effect was observed at the slow pace only.
Conclusions
Under simple rhythmic cues, an increase in pace causes spontaneous adjustments in spatial features (straighter hand paths) while preserving temporal ones (maximally-smoothed hand speeds). Complex rhythmical cues in contrast perturb spatiotemporal coupling and challenge movement control. These results may have important practical implications in motor rehabilitation.
ABSTRACT