SCANNING THE ISSUE The Plurality of Human BrainYComputer Interfacing

I . OVERVIEW The field of brainYcomputer interface (BCI) research began to develop about 25 years ago and transformed from initially isolated demonstrations by a few groups into a large scientific enterprise that is currently producing hundreds of peer-reviewed articles and several dedicated conferences and workshops each year. This level of productivity is reflective of the large and continually growing enthusiasm by the scientific community, funding agencies, and the public. BCI demonstrations described to date include seven-dimensional control of a robotic arm using implanted microelectrodes, three-dimensional control of a computer cursor using scalprecorded EEG, and spelling at a rate of more than 20 characters per minute using subdurally recorded ECoG. While most of these BCI demonstrations to date have been accomplished in animals or healthy human users, an increasing number of studies have shown that BCI systems can also be used by people with disabilities. These encouraging initial demonstrations of BCI technology have focused primarily on communication and control applications. More recently, a new area of research is emerging that aims to evaluate the utility of BCI techniques in the context of neurorehabilitation. This Special Issue on brain-computer interfacing is dedicated to this growing and diversifying research enterprise, and features important review articles as well as some important current examples of research in this area. Articles in the Special Issue describe new advanced signal and machine learning methods, the use of hybrid BCIs (hBCIs) for people with disabilities in the context of communication, control of a neuroprosthesis and control of a telepresence robot, as well as the application of BCI technology to neurorehabilitation in people with chronic stroke. The following paragraphs give brief introductions of the papers in this Special Issue.