Simulating the Effects of Neuromuscular Electrical Stimulation in the Injured Spinal Cord

Graduate #95
Discipline: Technology and Engineering
Subcategory: Biomedical Engineering

Ismael Perez - California State University, Los Angeles
Co-Author(s): Lin Tong, Patrick Arguello, and Jaya Nataraj, California State University, Los Angeles, CA

Central pattern generators (CPG) located in the spinal cord are capable of producing hindlimb stepping even without descending control, and are capable of being modified through spinal plasticity, for example, after spinal cord injury (SCI). Neuromuscular electrical stimulation (NMES) is being explored as an intervention to induce plasticity-related mechanisms of enhancing the CPG circuitry to create long-lasting rehabilitative effects. Experimental work in both animals and humans provide evidence that NMES has the potential to help rehabilitate walking in spinal cord injured subjects.

A computational model has been developed to study the effects of neuromuscular electrical stimulation on an injured spinal cord rodent model and examine feasible mechanisms by which NMES could enhance CPG control of stepping. This computational model consist of a 2-level spinal circuitry model, a finite element model for modeling the electric field that is being generated by NMES, and musculoskeletal biomechanics model (MSMS) driven by experimental data collected from our animal studies on NMES.

The computational model simulates an electric field generated from NMES, which will recruit motor units to activate the flexor muscle of the ankle, tibialis anterior. Furthermore, the neural activity from the spinal circuitry model will be provide inputs to the MSMS to generate locomotion for a spinal injured rodent model undergoing the therapy. The MSMS model will provide feedback to the spinal cord circuitry model, cutaneous stimulation for timing NMES, and provide an animation of the kinematics of the spinal injured rodent model. The 2-level spinal circuitry model is able to generate motoneuron phasic burst output. Preliminary simulations have demonstrated the feasibility of producing biomechanically realistic stepping when the musculoskeletal model is driven by experimental data. Interfacing both models will provide the capability to simulate and analyze the kinematic behavior of a non-injured spinal cord and injured spinal cord rodent model and with neuromuscular electrical stimulation applied at varying stimulation parameters. The combination of modeling every aspect of the therapy will provide an approach to explore feasible mechanism underlying observed outcomes and for formulating hypotheses on ways to optimize a therapy which potentially requires only non-invasive peripheral nerve stimulation coordinated with existing treadmill training approaches.

Not Submitted

Funder Acknowledgement(s): The funding for this work is provided by the National Science Foundation under Grant # HRD-1363399.

Faculty Advisor: Deborah Won, dwon@exchange.calstatela.edu