  Electroencephalogram (EEG) based brain-computer interfaces (BCI) may provide
a means of communication for those affected by severe paralysis. However, the
relatively low information transfer rates (ITR) of these systems, currently
limited to 1 bit/sec, present a serious obstacle to their widespread adoption
in both clinical and non-clinical applications. Here, we report on the
development of a novel noninvasive BCI communication system that achieves ITRs
that are severalfold higher than those previously reported with similar
systems. Using only 8 EEG channels, 6 healthy subjects with little to no prior
BCI experience selected characters from a virtual keyboard with sustained,
error-free, online ITRs in excess of 3 bit/sec. By factoring in the time spent
to notify the subjects of their selection, practical, error-free typing rates
as high as 12.75 character/min were achieved, which allowed subjects to
correctly type a 44-character sentence in less than 3.5 minutes. We hypothesize
that ITRs can be further improved by optimizing the parameters of the
interface, while practical typing rates can be significantly improved by
shortening the selection notification time. These results provide compelling
evidence that the ITR limit of noninvasive BCIs has not yet been reached and
that further investigation into this matter is both justified and necessary.
