Journal of Neuroscience Methods 170 (2008) 25–34 A combined wireless neural stimulating and recording system for study of pain processing Thermpon Ativanichayaphong a,1 , Ji Wei He b,1 , Christopher E. Hagains b,1 , Yuan B. Peng b,1 , J.-C. Chiao a,∗,1 a Electrical Engineering Department, The University of Texas at Arlington, Arlington, TX 76019, USA b Psychology Department, The University of Texas at Arlington, Arlington, TX 76019, USA Received 20 September 2007; received in revised form 11 December 2007; accepted 19 December 2007 Abstract Clinical studies have shown that spinal or cortical neurostimulation could significantly improve pain relief. The currently available stimulators, however, are used only to generate specific electrical signals without the knowledge of physiologically responses caused from the stimulation. We thus propose a new system that can adaptively generate the optimized stimulating signals base on the correlated neuron activities. This new method could significantly improve the efficiency of neurostimulation for pain relief. We have developed an integrated wireless recording and stimulating system to transmit the neuronal signals and to activate the stimulator over the wireless link. A wearable prototype has been developed consisting of amplifiers, wireless modules and a microcontroller remotely controlled by a Labview program in a computer to generate desired stimulating pulses. The components were assembled on a board with a size of 2.5 cm × 5 cm to be carried by a rat. To validate our system, lumbar spinal cord dorsal horn neuron activities of anesthetized rats have been recorded in responses to various types of peripheral graded mechanical stimuli. The stimulation at the periaqueductal gray and anterior cingulate cortex with different combinations of electrical parameters showed a comparable inhibition of spinal cord dorsal horns activities in response to the mechanical stimuli. The Labview program was also used to monitor the neuronal activities and automatically activate the stimulator with designated pulses. Our wireless system has provided an opportunity for further study of pain processing with closed-loop stimulation paradigm in a potential new pain relief method. Published by Elsevier B.V. Keywords: Pain; Neurostimulation; Single neuron recording; Telemetry; Electrophysiology; Dorsal horn 1. Introduction Chronic pain is a debilitating health problem. The impacts of pain suffering are not only on individual’s life quality but also on the family, society and national economics (Cramer and Spilker, 1997; Phillips, 2003). Several major approaches have been used to ease chronic pain, including surgical implanta- tion of neurostimulators. Neurostimulation on the spinal cord or primary motor cortex delivers low levels of electrical signals directly to nerve fibers or neurons to affect the neuronal mem- brane excitability, in turn to suppress pain signals by opening ∗ Corresponding author at: The University of Texas at Arlington, NH518, 416 Yates Street, Arlington, TX 76019, USA. Tel.: +1 817 272 1337; fax: +1 817 272 2253. E-mail address: jcchiao@uta.edu (J.-C. Chiao). 1 These authors contribute equally to this project. and closing of ion channels, through activation of descending inhibitory system. This form of therapy is attractive because it is selective for pain and has few side effects (Fields and Levine, 1984) compared to chemical approaches. Therapeutic studies have shown when used on carefully selected chronic pain patients, neurostimulation can significantly improve pain relief and reduce use of narcotic medications (North et al., 1991; Burchiel et al., 1996; Cameron, 2004; Bittar et al., 2005). The currently available stimulators, however, are open-loop systems in which the doctors can only obtain the results for pain management from patients’ verbal feedback. The stim- ulating signals are programmed during the installation of the devices and cannot be modified after the patients leave the hos- pital. Over time, the same stimulating configuration might not be effective to inhibit pain due to the possible resistance neurons may develop or the changes in the electrode-tissue interface. Our goal is to develop a closed-loop system that can automatically 0165-0270/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.jneumeth.2007.12.014