Brain–Computer Interfaces - Index of

Toward Ubiquitous BCIs 367
Across any of the major BCI non-invasive BCI approaches (P300, SSVEP, ERD),
about 10–30% of people cannot attain effective control [5, 6, 11, 14, 53, 55, 58,
60, 66, 75, 80]. This problem of reliability across subjects has been called BCI
illiteracy by some groups [35, 55, 66]. This term has various problems, including
the implication that BCI illiteracy reflects a lack of learning by the user [5, 8].
Work with a large group of subjects that were not pre-screened stated that most
untrained people can use an ERD BCI, even if their ITR is only a few bits per minute
[33]. However, that article assumed that subjects who attained greater than 60%
accuracy in a 2 choice task could use a BCI effectively. If the more common threshold
of 70% accuracy were used instead, more subjects would have been illiterate.
Similar work validated P300 and SSVEP BCIs across many users [2, 32].
It is true that, in some cases, people who cannot initially use a BCI can attain
control after training (see chapters “Neurofeedback Training for BCI Control” and
“BCIs in the Laboratory and at Home: The Wadsworth Research Program” in this
book). Improved signal processing or different instructions can also help. However,
some subjects are unable to produce the brain activity patterns needed to control
a specific BCI approach (such as ERD) no matter what. We recently showed that
switching to a different BCI approach could help such users [5]. This paper, and
other recent work [2, 8, 32, 54] also suggested that illiteracy may be worse in ERD
BCIs than SSVEP or P300 BCIs.
A recent major study addressed reliability across subjects in a noisy environment.
Our team ran 106 subjects in 6 days on an SSVEP BCI. All subjects had no prior
BCI experience and were recruited freely from visitors to our booth at the CeBIT
exhibition in Hannover in March 2008. We did not reject any potential subjects;
everyone who wanted to be a subject got to be a subject. CeBIT was a huge public
exhibition with extreme electrical noise and many distractions.
There were no problems with preparing, running, or cleaning any subject.
Questionnaires showed that the system was not annoying nor fatiguing to most
users. Most subjects could spell with this system. Some subjects who initially could
not attain effective control performed better after lighting, display, or signal processing
parameters were changed. Performance tended to be worse among older
and male subjects [2].
BCIs should also work reliably any time a user wants to communicate. Relevant
EEG patterns can change within and across days. BCIs need to adapt to such
changes.
Another facet of reliability is robustness to environmental noise. Many of us in
the BCI research community had a field BCI recording session go awry because
of an air conditioner motor, generator, refrigerator motor, or medical device (see
chapter “Brain–Computer Interfaces for Communication and Control in Locked-in
Patients”). This is becoming less of a concern with better amplifiers, sensors, noise
reduction software, and wireless systems that avoid the electrical noise that can be
produced along cables. As noted above, many studies and companies have described
BCIs that can operate in very noisy settings.
While BCI reliability needs to improve, it does not need to be perfect before
BCIs gain wider adoption. Mainstream interfaces also do not work for many