Contribution of Corticospinal Modulation and Total Electrical Energy for Peripheral-Nerve-Stimulation-Induced Neuroplasticity as Indexed by Additional Muscular Force

Abstract

Background: Protocols to induce motor related neuroplasticity are usually directed to central neural structures such as the motor cortex or the spinal cord.

Objective: Herein, we aimed to evaluate the effects of peripheral nerve stimulation using a current intensity (stimulation intensity) approach to understand the contribution of the corticospinal system and total energy to electrically-induced neuroplasticity.

Methods: Electrical stimulation trains of lower intensity, interlaced with 2-s bursts of higher intensity, were applied to anesthetized rabbits. Nerve blocks were applied to the proximal side of the stimulation site with identical stimulation trains in a different session to block the contribution of corticospinal volleys during intensity-modulated electrical stimulation.

Results: Additional force corresponding to additional recruitment of motoneurons was observed when a 2-s burst of high intensity was present (burst/constant: 24.7 ± 3.6%/2.09 ± 4.8%; p < .001). Additional force was absent in sessions when the neural pathway to the spinal cord was blocked (unblocked/blocked: 29.3 ± 3.8%/-2.49 ± 4.8%; p < .001).

Conclusions: The results suggest that induced neuroplasticity indexed by the additional force is dependent on the total energy applied and connectivity to central structures. These results give additional evidence for the contribution of two factors for induced neuroplasticity: (i) modulation by corticospinal structures and (ii) total energy of stimulation. Further protocols should explore simultaneous peripheral and central stimulation.

Keywords: Electrical stimulation; Frequency; Intensity; Neuroplasticity; Peripheral nerve stimulation.