Hybrid Optical–Electrical Brain Computer Interfaces, Practices and Possibilities

In this chapter we present an overview of the area of electroencephalographyfunctional near infrared spectroscopy (EEG-fNIRS) measurement as an activity monitoring technology for brain computer interfacing applications. Our interest in this compound neural interfacing technology is motivated by a need for a motor cortical conditioning technology suitable for use in a neurorehabilitation setting [15, 50]. Specifically we seek BCI technology that allows a patient with a paretic limb (as a consequence of stroke) to engage in movement-based rehabilitation exercises which will, we hope, encourage neuroplastic processes in the brain so that recovery and function is ultimately restored [38]. As we are interested in rehabilitation following stroke haemodynamic signatures of motor cortical activity coupled with the corresponding direct measures of the electrical activity of the neurons involved could be a rich source of new information on the recovering brain areas. While most neural engineers will be familiar with the concepts underpinning the electroencephalogram (EEG), the same cannot be said for fNIRS. Consequently this chapterwill discussmuch of the foundational concepts underlying this measurement before describing an EEG-fNIRS probe and early experiments which illustrate the concept and highlight aspects of the utility of this hybrid BCI approach