Baseband Signal Transmission Experiment for Intra-Brain Communication with Implantable Image Sensor Kiyotaka Sasagawa, Shogo Yokota, Takashi Matsuda, Peter Davis, Bing Zhang, Keren Li, Takuma Kobayashi, Toshihiko Noda, Takashi Tokuda and Jun Ohta Abstract— We demonstrate image signal transmission for wireless intra-brain communication. As a preliminary exper- iment, transmission characteristics of the brain phantom were measured. The baseband output signal from an implantable complementary metal-oxide-semiconductor (CMOS) image sen- sor is transmitted through the phantom. The image was successfully reproduced from the received signal. I. INTRODUCTION Neural activities in the brain are of considerable interest to researchers in the fields of medicine and biology. Especially, we are interested in simultaneous multi-area imaging in order to observe cooperative activities between brain areas. An implantable complementary-metal-oxide (CMOS) image sensor is expected to be a solution. By the virtue of advanced CMOS technology, small image sensors have been designed and fabricated [1]–[5]. Such sensors are implantable even in a small mouse brain with low invasiveness. In previous works, neural activities in a mouse brain have been successfully observed by the sensors [5], [6] and can take images while the mouse is moving freely [4]. However, it is difficult to implant a lot of the sensors in the mouse brain because the number of wires is increased with the number of the sensors. In order to solve the problem, wireless communication techniques are required. We have proposed the distributed implantable image sensor system as shown in Fig. 1 [7]. In this method, signals are transmitted from image sensors to a receiver placed on a brain surface without any metal wires [8]. It is known that living tissues can be used as transmission media [9]–[13]. Thus, it could be possible to send images from implantable image sensors. An extracorporeal device is placed on the back of a mouse. The image data is sent from the sensor to the extracorporeal device through the brain. In previous work, the signal modulated with image sensor output at a carrier frequency of 50 MHz was send through a brain and images were successfully received. If the baseband This work was supported by Core Research for Evolutional Science and Technology, Japan Science and Technology Agency. K. Sasagawa, S. Yokota, T. Kobayashi, T. Noda, T. Tokuda and J. Ohta are with Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan, and also with the Japan Science and Technology Agency, Core Research for Evolutional Science and Technology (JST-CREST), 4-1-8 Honcho, Kawaguchi, Saitama 331-0012, Japan. sasagawa@ms.naist.jp Takashi Matsuda, Bing Zhang and Keren Li are with New Generation Wireless Communications Research Center, National Institute of Infor- mation and Communications Technology. 3-4, Hikarino-Oka, Yokosuka, Kanagawa 239-0847, Japan Peter Davis is with Telecognix Corpolation. 58-13 Yoshida Shimooji-cho, Sakyo-ku, Kyoto 606-8314, Japan Fig. 1. Concept of distributed implantable CMOS image sensor system. signal from the sensor can be directly transmitted, no mod- ulation circuit is required for the implantable image sensor. Thus, it would be expected to be less invasive and more power efficient. In this study，we demonstrate transmission of the base- band image sensor signal through a brain phantom. We measured transmission characteristics of a mouse brain at frequencies around the clock frequency of our image sensor and verified that it is possible to communicate through a mouse brain with miniature electrodes. The output signal from an implantable image sensor is transmitted through a brain phantom and the image are successfully reproduced from the received signal. II. S IGNAL TRANSMISSION EXPERIMENT THROUGH BRAIN PHANTOM By utilizing the conductive property of a brain tissue, it would be possible to transmit signals with low power consumption. In this work, we demonstrate the transmission of a signal from an image sensor without any metal wires. In order to verify the capability of wireless image transmission, a brain phantom is used. Because it is confirmed that the signal transmission characteristic of the phantom is similar to the real mouse brain, we used the phantom for primitive experiments in this work. The brain phantom was prepared from phosphate-buffered saline mixed with 1% agar. The electrode used in the experiment is shown in Fig. 2. A 0.5 mm 0.5 mm electrode for signal is placed on the front side. And, a 3.5 mm 3.5 34th Annual International Conference of the IEEE EMBS San Diego, California USA, 28 August - 1 September, 2012 6011 978-1-4577-1787-1/12/$26.00 ©2012 IEEE