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Vagus Nerve Stimulation Induced Motor Map Plasticity Does Not Require Cortical Dopamine
Jackson Brougher1, Camilo A Sanchez2, Umaymah S Aziz1
1Department of Neuroscience, University of Texas at Dallas, Richardson, TX, United States.
Frontiers in Neuroscience
|September 9, 2021
Summary
Vagus nerve stimulation (VNS) enhances motor cortex plasticity after stroke, even without dopamine. This suggests VNS uses unique pathways to promote brain recovery and motor skill learning.
Area of Science:
- Neuroscience
- Rehabilitation Medicine
- Neuroplasticity
Background:
- Vagus nerve stimulation (VNS) combined with motor rehabilitation is a promising strategy for functional recovery after neural injuries like stroke.
- VNS drives neuroplasticity in the motor cortex (M1), crucial for its therapeutic effects, but the exact mechanisms are unclear.
- Cortical dopamine (DA) is vital for M1 plasticity and motor learning, yet its role in VNS efficacy remains untested.
Purpose of the Study:
- To investigate the effect of cortical dopamine depletion on VNS-induced motor cortex plasticity.
- To determine if dopamine is essential for the neuroplastic changes observed with VNS.
Main Methods:
- Rats were trained on a skilled reaching task before VNS electrode implantation and dopamine depletion in M1 using 6-hydroxydopamine (6-OHDA).
- Following training-paired VNS, cortical motor mapping and lesion validation were performed to assess changes.
Main Results:
- VNS increased motor map representations for proximal forelimb muscles and decreased those for distal forelimb muscles in both intact and dopamine-depleted rats.
- VNS increased tyrosine hydroxylase (TH+) fiber density in intact M1, but this effect was absent in dopamine-depleted hemispheres.
Conclusions:
- Dopamine is not required for VNS-induced motor cortex plasticity, despite VNS likely upregulating catecholaminergic signaling.
- VNS may promote neocortical plasticity through distinct neuromodulatory pathways, differing from those engaged during skill acquisition that rely heavily on dopamine.
