Simultaneous transcranial magnetic stimulation and single-neuron recording in alert non-human primates.

Transcranial magnetic stimulation (TMS) is a widely used, noninvasive method for stimulating nervous tissue, yet its mechanisms of effect are poorly understood. Here we report new methods for studying the influence of TMS on single neurons in the brain of alert non-human primates. We designed a TMS coil that focuses its effect near the tip of a recording electrode and recording electronics that enable direct acquisition of neuronal signals at the site of peak stimulus strength minimally perturbed by stimulation artifact in awake monkeys (Macaca mulatta). We recorded action potentials within ∼1 ms after 0.4-ms TMS pulses and observed changes in activity that differed significantly for active stimulation as compared with sham stimulation. This methodology is compatible with standard equipment in primate laboratories, allowing easy implementation. Application of these tools will facilitate the refinement of next generation TMS devices, experiments and treatment protocols

Complications of epidural spinal stimulation: lessons from the past and alternatives for the future

Study design Systematic review. Objectives Over the past decade, an increasing number of studies have demonstrated that epidural spinal cord stimulation (SCS) can successfully assist with neurorehabilitation following spinal cord injury (SCI). This approach is quickly garnering the attention of clinicians. Therefore, the potential benefits of individuals undergoing epidural SCS therapy to regain sensorimotor and autonomic control, must be considered along with the lessons learned from other studies on the risks associated with implantable systems. Methods Systematic analysis of literature, as well as preclinical and clinical reports. Results The use of SCS for neuropathic pain management has revealed that epidural electrodes can lose their therapeutic effects over time and lead to complications, such as electrode migration, infection, foreign body reactions, and even SCI. Several authors have also described the formation of a mass composed of glia, collagen, and fibrosis around epidural electrodes. Clinically, this mass can cause myelopathy and spinal compression, and it is only treatable by surgically removing both the electrode and scar tissue. Conclusions In order to reduce the risk of encapsulation, many innovative efforts focus on technological improvements of electrode biocompatibility; however, they require time and resources to develop and confirm safety and efficiency. Alternatively, some studies have demonstrated similar outcomes of non-invasive, transcutaneous SCS following SCI to those seen with epidural SCS, without the complications associated with implanted electrodes. Thus, transcutaneous SCS can be proposed as a promising candidate for a safer and more accessible SCS modality for some individuals with SCI