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Motor programmes for goal-directed movements are continuously adjusted according to changes in target location
J F van Sonderen1, C C Gielen, J J Denier van der Gon
1Department of Medical and Physiological Physics, University of Utrecht, The Netherlands.
Experimental Brain Research
|January 1, 1989
Summary
Human arm movements adjust mid-flight when target locations change. This study shows motor programs are updated centrally, modifying trajectories within milliseconds of movement initiation.
Area of Science:
- Neuroscience
- Motor Control
- Biomechanics
Background:
- Previous research indicated initial arm movement direction in double-step stimuli is intermediate to target locations.
- This intermediate direction suggests a continuously shifting internal target representation.
Purpose of the Study:
- To investigate if arm movement trajectories are modified during execution in response to a second target presentation.
- To determine the timing of trajectory modifications in fast arm movements.
Main Methods:
- Studied fast, two-dimensional arm movements in response to double-step visual stimuli.
- Utilized an inter-stimulus interval of 100 ms to isolate trajectory modification effects.
- Analyzed movement trajectories for deviations from the initial path.
Main Results:
- Arm movement trajectories significantly deviate from their initial path within 60 ms of movement onset.
- Trajectory modifications can occur as early as 30 ms after movement initiation.
- These findings demonstrate real-time adjustments to motor commands.
Conclusions:
- Motor programs are centrally modified during execution based on updated target information.
- Hypothesized that motor program generation begins post-target presentation, with continuous muscle activation adjustments.
- Suggests a dynamic internal target representation guides ongoing movement execution.