An expanded cortical representation for hand movement after peripheral motor denervation.

Area of Science:

• Neuroscience
• Motor Control
• Neuroplasticity

Background:

• Functional reorganization of the motor cortex is known in animals after peripheral nerve damage.
• Previous studies have not specifically investigated human motor cortex changes after peripheral motor denervation.

Purpose of the Study:

• To investigate functional changes in the human motor cortex following peripheral motor denervation.
• To differentiate adaptive changes from those related to increased effort due to weakness.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to assess brain activation during a finger movement task.
• Patients with pure motor neuropathy, pure sensory neuropathy, and healthy controls were studied.
• Patients with inclusion body myositis (weakness) were included to control for effort-related changes.

Main Results:

• Patients with motor neuropathy showed increased motor cortex activation (ipsilateral and contralateral) and posterior shifts in sensorimotor cortex localization.
• Pure sensory neuropathy patients showed no change in activation extent and a trend for anterior shifts.
• Patients with weakness due to myositis showed no significant differences in activation compared to controls.

Conclusions:

• Peripheral denervation, distinct from weakness, induces functional reorganization in the adult sensorimotor cortex.
• Adaptive responses to motor denervation involve both central and peripheral nervous systems.
• This study provides novel evidence for central nervous system adaptation to peripheral motor loss in humans.