Sensor technology

This chapter deals with an overview of sensors used in the collection of data for Brain-Computer Interface (BCI) technology. For the purposes of this chapter, we divide sensor technologies into two basic categories. First, we discuss invasive technologies, which entail brain surgery procedures for implantation involving primarily multielectrode recordings from arrays of microelectrodes implanted directly into the brain to measure action potentials from single cells. This is a major growth area for sensor technologies and will be the major focus of this chapter. However, we caution that most of this technology is under development in animal models and is not yet approved for human use. In addition, measurements from subdural or epidural strips of electrode arrays used to record cortical potentials somewhat analogous to EEG-type recordings on the surface of the skull will be discussed, as this is currently the greatest application for use of these invasive electrodes in humans for (primarily) epilepsy surgery. However, this could help increase the growth of other BCI applications. Second, we discuss noninvasive technologies, which primarily involve multielectrode EEG recording arrays of wet silver (Ag) or gold (Au) conducting paste electrodes that are placed on the surface of the skull to record EEG activity. These electrodes are commercially available from a number of sources, but surprisingly, there has been limited growth in this area. We caution that noninvasive electrodes have largely been used acutely and may be more invasive to the scalp when used in future, more chronic, applications of BCI technology by humans at home or work. Additional tech-nology development in this area will be briefly discussed.