Journal of Neuroscience Methods 204 (2012) 341–348 Contents lists available at SciVerse ScienceDirect Journal of Neuroscience Methods jou rnal h om epa ge: www.elsevier.com/locate/jneumeth Clinical Neuroscience A fully implanted programmable stimulator based on wireless communication for epidural spinal cord stimulation in rats Hui Zhou a , Qi Xu a,∗ , Jiping He a,c , Hangkong Ren b , Houlun Zhou b , Kejia Zheng a a Key Laboratory of Image Processing and Intelligent Control, Department of Control Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074, China b Department of Anatomy, Tongji Medical College, Huazhong University of Science and Technology, China c Center for Neural Interface Design and School of Biological and Health Systems Engineering, Arizona State University, United States a r t i c l e i n f o Article history: Received 11 June 2011 Received in revised form 5 October 2011 Accepted 28 October 2011 Keywords: Implantable stimulator Epidural spinal cord stimulation EMG Telemetry Rat a b s t r a c t Clinical research indicates that the epidural spinal cord stimulation (ESCS) has shown potential in pro- moting locomotor recovery in patients with incomplete spinal cord injury (ISCI). This paper presents the development of a fully implantable voltage-regulated stimulator with bi-directional wireless communi- cation for investigating underlying neural mechanisms of ESCS facilitating motor function improvement. The stimulation system consists of a computer, an external controller, an implantable pulse generator (IPG), a magnet, the extension leads and a stimulation electrode. The telemetry transmission between the IPG and the external controller is achieved by a commercially available transceiver chip with 2.4 GHz carrier band. The magnet is used to activate the IPG only when necessary to minimize the power consump- tion. The encapsulated IPG measures 33 mm × 24 mm × 8 mm, with a total mass of ∼12.6 g. Feasibility experiments are conducted in three Sprague-Dawley rats to validate the function of the stimulator, and to investigate the relationship between lumbar-sacral ESCS and hindlimb electromyography (EMG) responses. The results show that the stimulation system provides an effective tool for investigation of ESCS application in motor function recovery in small animals. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Since 1967 (Shealy et al., 1967), the epidural spinal cord stimulation (ESCS) has become an established and widely adopted treatment for chronic pain. Recently, ESCS has shown positive effects in facilitating locomotor recovery in individuals with incomplete spinal cord injury (ISCI) and multiple sclerosis (MS) (Cook and Weinstein, 1973; Davis et al., 1981; Tallis et al., 1983). Dimitrijevic and his colleagues reported that ESCS at 25–50 Hz elicited rhythmic lower limb flexion/extension movements, while at 5–15 Hz initiated lower limb extension movements in spinal cord injured (SCI) individuals in supine position (Dimitrijevic et al., 1998; Jilge et al., 2004; Minassian et al., 2007). In their experiments, an implantable system was used to provide epidural stimulation of spinal cord in patients. By combining ESCS with partial weight-bearing therapy, Herman and his team (Carhart et al., 2004; He and Herman, 2010; Herman et al., 2002) inves- tigated a protocol for facilitating over-ground ambulation in wheelchair dependent individuals with chronic, incomplete spinal cord injury. In their clinical research, an externally powered ESCS ∗ Corresponding author. Tel.: +86 27 87557284. E-mail address: xuqi@mail.hust.edu.cn (Q. Xu). system was used to provide high stimulation power and long pulse duration (up to 1000 s). The system consisted of an implanted receiver (X-trel 3470), a pair of implanted quadripolar electrode leads (PISCES-Quad Plus, Model 3888), the dual implanted lead extensions, an external transmitter (X-trel, Model 3425), and an external antenna (Model 3440). The X-trel external transmitter powered the implanted receiver via transcutaneous RF telemetry. Their results demonstrated that ESCS with a frequency of 20–40 Hz, a pulse width of 800 s, and the amplitude between the sensory and motor threshold had effective influence on the motor system (He and Herman, 2008; Huang et al., 2006). Although these studies have indicated that ESCS can promote locomotor recovery in ISCI patients, an optimal protocol and the underlying neural mechanisms of this therapy remain unclear. It is desirable to conduct further research to decipher the potential mechanisms for the exploration of optimal protocols and stimu- lating parameters to guide the future clinical application of this promising treatment for motor function recovery after severe neu- ral injury. It has been demonstrated that ESCS applied at the L2 segment in the rat spinal cord isolated from brain control can induce bilateral stepping patterns most readily when compared with stimulation at other spinal segments (Gerasimenko et al., 2008; Ichiyama et al., 2005). In their animal experiments, the stimulation electrodes were made of stainless steel microwire 0165-0270/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jneumeth.2011.10.028