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Background: Several neural interface technologies that stimulate and/or record from groups of axons have been developed. The longitudinal intrafascicular electrode (LIFE) is a fine wire that can provide access to a discrete population of axons within a peripheral nerve fascicle. Some applications require, or would benefit greatly from, technology that could provide access to multiple discrete sites in several fascicles., New Method: The distributed intrafascicular multi-electrode (DIME) lead was developed to deploy multiple LIFEs to several fascicles. It consists of several (e.g. six) LIFEs that are coiled and placed in a sheath for strength and durability, with a portion left uncoiled to allow insertion at distinct sites. We have also developed a multi-lead multi-electrode (MLME) management system that includes a set of sheaths and procedures for fabrication and deployment., Results: A prototype with 3 DIME leads was fabricated and tested in a procedure in a cadaver arm. The leads were successfully routed through skin and connective tissue and the deployment procedures were utilized to insert the LIFEs into fascicles of two nerves., Comparison With Existing Method(s): Most multi-electrode systems use a single-lead, multi-electrode design. For some applications, this design may be limited by the bulk of the multi-contact array and/or by the spatial distribution of the electrodes., Conclusion: We have designed a system that can be used to access multiple sets of discrete groups of fibers that are spatially distributed in one or more fascicles of peripheral nerves. This system may be useful for neural-enabled prostheses or other applications., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Neuromuscular electrical stimulation (NMES) can be used to activate paralyzed or paretic muscles to generate functional or therapeutic movements. The goal of this research was to develop a rodent model of NMES-assisted movement therapy after spinal cord injury (SCI) that will enable investigation of mechanisms of NMES-induced plasticity, from the molecular to systems level. Development of the model requires accurate mapping of electrode and muscle stimulation sites, the capability to selectively activate muscles to produce graded contractions of sufficient strength, stable anchoring of the implanted electrode within the muscles and stable performance with functional reliability over several weeks of the therapy window. Custom designed electrodes were implanted chronically in hindlimb muscles of spinal cord transected rats. Mechanical and electrical stability of electrodes and the ability to achieve appropriate muscle recruitment and joint angle excursion were assessed by characterizing the strength duration curves, isometric torque recruitment curves and kinematics of joint angle excursion over 6-8 weeks post implantation. Results indicate that the custom designed electrodes and implantation techniques provided sufficient anchoring and produced stable and reliable recruitment of muscles both in the absence of daily NMES (for 8 weeks) as well as with daily NMES that is initiated 3 weeks post implantation (for 6 weeks). The completed work establishes a rodent model that can be used to investigate mechanisms of neuroplasticity that underlie NMES-based movement therapy after spinal cord injury and to optimize the timing of its delivery.

Neuromuscular electrical stimulation (NMES) can provide functional movements in people after central nervous system injury. The neuroplastic effects of long-term NMES-induced repetitive limb movement are not well understood. A rodent model of neurotrauma in which NMES can be implemented may be effective for such investigations. We present a rodent model for NMES of the flexor and extensor muscles of the hip, knee, and ankle hindlimb muscles. Custom fabricated intramuscular stimulating electrodes for rodents were implanted near identified motor points of targeted muscles in ten adult, female Long Evans rats. The effects of altering NMES pulse stimulation parameters were characterized using strength duration curves, isometric joint torque recruitment curves and joint angle measures. The data indicate that short pulse widths have the advantage of producing graded torque recruitment curves when current is used as the control parameter. A stimulus frequency of 75 Hz or more produces fused contractions. The data demonstrate ability to accurately implant the electrodes and obtain selective, graded, repeatable, strong muscle contractions. Knee and ankle angular excursions comparable to those obtained in normal treadmill walking in the same rodent species can be obtained by stimulating the target muscles. Joint torques (normalized to body weight) obtained were larger than those reported in the literature for small tailed therian mammals and for peak isometric ankle plantarflexion in a different rodent species. This model system could be used for investigations of NMES assisted hindlimb movement therapy.

Upper extremity neuromuscular electrical stimulation (FNS) has long been utilized as a neuroprosthesis to restore hand-grasp function in individuals with neurological disorders and injuries. More recently, electrical stimulation is being used as a rehabilitative therapy to tap into central nervous system plasticity. Here, we present initial development of a rodent model for neuromuscular stimulation induced forelimb movement that can be used as a platform to investigate stimulation-induced plasticity. The motor points for flexors and extensors of the shoulder, elbow, and digits were identified and implanted with custom-built stimulation electrodes. The strength-duration curves were determined and from these curves the appropriate stimulation parameters required to produce consistent isolated contraction of each muscle with adequate joint movement were determined. Using these parameters and previous locomotor EMG data, stimulation was performed on each joint muscle pair to produce reciprocal flexion/extension movements in the shoulder, elbow, and digits, while 3D joint kinematics were assessed. Additionally, co-stimulation of multiple muscles across multiple forelimb joints was performed to produce stable multi-joint movements similar to those observed during reach-grasp-release movements. Future work will utilize this model to investigate the efficacy and underlying mechanisms of forelimb neuromuscular stimulation therapy to promote recovery and plasticity after neural injury in rodents.