Pushing the Communication Speed Limit of a Noninvasive BCI Speller

TL;DR

This paper introduces a noninvasive EEG-based BCI system that significantly surpasses previous information transfer rates, enabling faster and more efficient communication for users with severe paralysis.

Contribution

The study demonstrates a novel BCI system achieving over 3 bit/sec ITR with only 8 EEG channels, and practical typing rates up to 12.75 characters per minute, surpassing prior limits.

Findings

Achieved online ITRs over 3 bit/sec with 8 EEG channels.

Enabled typing of a 44-character sentence in less than 3.5 minutes.

Potential for further improvements by optimizing interface parameters.

Abstract

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.