High Force Unimanual Handgrip Contractions Increase Ipsilateral Sensorimotor Activation and Functional Connectivity

Area of Science:

• Neuroscience
• Motor Control
• Brain Imaging

Background:

• Classical understanding posits focal contralateral areas control unimanual force.
• Emerging evidence highlights the role of bilateral brain networks.
• Hemispheric-specificity and network activation scaling require further investigation.

Purpose of the Study:

• To investigate how increasing unimanual voluntary force affects sensorimotor network activation and functional connectivity.
• To examine the hemispheric-specificity of brain network responses during graded force production.
• To elucidate the relationship between force intensity and sensorimotor network engagement.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was employed.
• Participants performed right-handgrip contractions at 25%, 50%, and 75% of maximal voluntary contraction (MVC).
• Analysis focused on bilateral sensorimotor network activation and functional connectivity.

Main Results:

• High force (75% MVC) contractions showed greater ipsilateral motor cortex activation compared to low force (25% MVC).
• Increased force levels correlated with enhanced ipsilateral sensorimotor activation and network strength.
• Greater functional connectivity between hemispheres within the sensorimotor network was observed with higher force.

Conclusions:

• Force intensity parametrically modulates ipsilateral sensorimotor network activation.
• Increased unimanual force enhances interhemispheric functional connectivity within the sensorimotor network.
• Sensorimotor network engagement, not just focal areas, is crucial for voluntary force generation and scales with intensity.