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Reaching to ipsilateral or contralateral targets: within-hemisphere visuomotor processing cannot explain hemispatial
D P Carey1, E L Hargreaves, M A Goodale
1Department of Psychology, University of Western Ontario, London, Canada. d.carey@abdn.ac.uk
Experimental Brain Research
|December 1, 1996
Summary
Motor control advantages for aiming movements depend on the response direction, not target location. These findings suggest biomechanical constraints, rather than visual processing, influence movement efficiency.
Area of Science:
- Neuroscience
- Motor Control
- Human Movement Science
Background:
- Ipsilateral aiming movements (same side of the body) typically show performance advantages over contralateral movements.
- This is often attributed to more efficient intrahemispheric processing in the brain.
Purpose of the Study:
- To investigate whether aiming movement advantages are linked to target visual field or motor response direction.
- To test the hypothesis that intrahemispheric processing underlies ipsilateral advantages.
Main Methods:
- Examined kinematic data of aiming movements in 26 right-handed subjects.
- Subjects aimed to targets in left and right visual fields, sometimes towards the target and sometimes to its mirror image.
- Analyzed reaction time, peak velocity, movement duration, and deceleration phases.
Main Results:
- Movement advantages (peak velocity, duration, deceleration) were associated with the direction of the motor response, not the visual target location.
- These effects were more pronounced for the right hand, especially in deceleration.
- Hemispatial differences in performance were independent of the visual hemifield of target presentation.
Conclusions:
- Findings challenge the intrahemispheric processing hypothesis for ipsilateral aiming advantages.
- Results support models emphasizing biomechanical constraints on contralateral movements.
- Motor response direction, not visual hemispace, is a key factor in movement kinematics.