A Wireless Integrated Microsystem for Single-Unit Recording in Primate Motor Cortex
There is growing interest in recording neural activity in the motor cortex of the brain on a long-term basis. In cases of paralysis due to spinal cord injury (paraplegics and quadriplegics), the signals needed to control movement may still be present in the cortex but are no longer being transmitted to the peripheral limbs to facilitate muscle control, and the hope is to be able to restore at least limited mobility to paralyzed individuals by literally wiring around the break in the spinal cord. The realization of such microsystems requires the successful integration of high-density electrode arrays, cables for connecting the electrode signals to integrated amplifiers, an implantable signal processor for separating the signals of interest (neural spikes) from background noise, and an inductively-coupled wireless link providing power and command signals to the implant while transmitting the neural signals to the outside world. A microsystem for performing these functions will be described. The system consists of 64-256 electrode sites distributed in three dimensions with site separations of 200-400Â µm. The neural signals from these sites are amplified by a gain of 1000 using capacitively-coupled recording amplifiers and are transmitted to a neural processing chip that identifies the neural spikes and formats them in 18-bit words. These words are Manchester-encoded for transmission to the outside world over a 100-200MHz wireless link. The entire microsystem is powered over an RF-carrier at 8MHz and operates at less than 20mW. Command information is supplied to the implant over the same carrier. We hope to have such microsystems operating in primates by the end of the year. They could launch revolutionary progress in understanding the signal processing techniques used in the nervous system as well as establishing a basis for treating paralysis in ways never before possible.
Kensall D. Wise received the BSEE degree with highest distinction from Purdue University in 1963 and the MS and Ph.D. degrees in electrical engineering from Stanford University in 1964 and 1969, respectively. Since 1974, he has been a faculty member at the University of Michigan, where he is now the William Gould Dow Distinguished University Professor of Electrical Engineering and Computer Science and the Director of the Engineering Research Center for Wireless Integrated MicroSystems. He is a Fellow of the IEEE, a Fellow of the AIMBE, and a member of the United States National Academy of Engineering.
Amir M. Sodagar received the B.S., M.S., and Ph.D. degrees from K.N.Toosi University of Technology (KNTU) and Iran University of Science and Technology (IUST), Tehran, Iran, all in Electrical Engineering in 1992, 1995, and 2000, respectively. From 1992 to 2000 he was with S. Rajaee University (SRU) as a Lecturer. After receiving the Ph.D. degree until 2002 he was with the University of Michigan as a Post-Doctoral Research Fellow. From 2002 to 2004 he was with SRU and KNTU as an Assistant Professor and an Adjunct Professor, respectively. Dr. Sodagar was known as the IUST's Outstanding E.E. Grad. Student in 1995 and IUST's Best Ph.D. Reseacher in 2000. He was also the recipient of SRU's Distinguished Faculty Member Award in 1999 and 2000, and SRU's Distinguished Researcher Award in 2003. He has been with the NSF ERC for WIMS since 2004 as an Associate Visiting Research Scientist.