Force perception at the shoulder after a unilateral suprascapular nerve block

Area of Science:

• Motor control
• Neuroscience
• Biomechanics

Background:

• Force matching relies on centrally generated sense of effort and peripheral sensory signals.
• The relative importance of these two information sources remains debated.
• The corollary discharge hypothesis posits central motor commands are key for force matching.

Purpose of the Study:

• To examine shoulder force matching accuracy before and after a suprascapular nerve block.
• To investigate the impact of induced sensory-muscle force mismatch on force matching.
• To differentiate the contributions of sensory feedback and sense of effort in motor tasks.

Main Methods:

• Participants performed shoulder torque matching tasks.
• A suprascapular nerve block was administered to disrupt peripheral sensation.
• Electromyography (EMG) of the deltoid muscle was recorded.
• Torque matching accuracy and error were analyzed pre- and post-nerve block.

Main Results:

• Torque matching accuracy remained unchanged after the suprascapular nerve block.
• Torque errors aligned directionally with predictions of the corollary discharge hypothesis.
• A significant mismatch in deltoid muscle activity (EMG) occurred post-block, exceeding torque error changes.

Conclusions:

• Findings support the utilization of sensory information in force matching tasks.
• The suprascapular nerve block induced a sensory disruption, complicating interpretation of sensory reweighting.
• A role for the sense of effort in force matching persists, despite sensory alterations.