Arm-trunk coordination in the absence of proprioception

Area of Science:

• Neuroscience
• Biomechanics
• Motor Control

Background:

• Trunk motion influences hand trajectory during reaching.
• Arm configuration changes typically compensate for trunk motion.
• The role of proprioception in this compensatory mechanism is not fully understood.

Purpose of the Study:

• To investigate the role of proprioception in compensating for trunk motion during reaching.
• To compare compensatory strategies in deafferented versus healthy individuals.

Main Methods:

• Healthy and deafferented subjects performed reaching movements to ipsilateral and contralateral targets.
• Trunk motion was sometimes mechanically blocked.
• No visual feedback was provided; movements were analyzed for hand trajectory and joint coordination.

Main Results:

• Healthy subjects maintained invariant hand trajectories regardless of trunk motion.
• Deafferented subjects showed significant, though incomplete, compensation, particularly for ipsilateral targets.
• Compensation in deafferented subjects involved rapid adjustments in arm joint angles, similar to healthy controls.

Conclusions:

• Proprioception significantly contributes to compensatory control of reaching movements during trunk motion.
• Even without proprioception and vision, substantial compensation occurs, suggesting involvement of other sensory systems like vestibulospinal pathways.
• The findings highlight the brain's remarkable ability to adapt motor control strategies under sensory deprivation.