Brain–Computer Interfaces - Index of

370 B.Z. Allison
The commercial ramifications of overcoming this problem are considerable. If
such a system could offer improved performance, it could appeal to anyone who
uses conventional interfaces. If a gamer using an integrated BCI/hand controller
can defeat an otherwise equally skilled gamer using hand controllers alone on a
popular game – even periodically – the resulting shockwave through the massive
and growing gaming community will hearken the end of gaming as we know it.
BCIs could be used in combination with other assistive communication technologies.
The second (complementary) interface could influence one or more of
the three components of ITR. Accuracy could be improved, and/or selection time
reduced, if the BCI can help identify the desired message. For example, an SSVEP
system might facilitate an eye tracking system’s decision about where a user is looking/attending.
If a user can send one of four signals by moving his tongue in one of
four directions, and five seconds are needed per selection due to unreliable motor
control, a system might simultaneously present the four options via a P300 BCI.
Or, perhaps an ERD BCI could provide additional information about a user’s motor
intent. Alternately, the add-on interface could increase the number of selections. If
a 4-choice BCI allows a user to select one of four wheelchair directions, an EMG
switch might be used to indicate “discrete” or “continuous” motion. (That is, instruct
the wheelchair to either go forward 100 cm, or continue going forward.) This would
effectively double the N, the number of signals available. The add-on signal might
also be used in simultaneous or interleaved fashion, meaning that users might use
both interfaces at once, as in the above examples, or might use them separately.
For example, if an eye tracking system is fatiguing, a user might use the eye
tracker to move a cursor around the screen, and then use a BCI to choose what to do
at a target location. This would allow the user frequent rest periods.
Very recent work showed that people can use two different BCIs at the same
time [5, 57]. “Hybrid” BCIs like these are different from earlier work that described
efforts to combine different SSVEP approaches with multiple targets [6, 50], or ERD
BCIs in which users imagine multiple movements [28, 45, 62]. However, the idea
of combining different BCIs, which was first presented in a citable format in [10],
has received little attention until recently, and is revolutionary in the Kuhnian sense.
This means that the idea is not simply new, but a major change from the dominant
paradigm that is not currently envisioned or accepted by mainstream expert
researchers 4 .
In a recent study, 14 subjects participated in three conditions. In the first condition,
subjects would imagine left hand movement after a left cue, and right hand
movement after a right cue. In the second condition, subjects would focus on a left
LED after a left cue, and a right LED after a right cue. In the third condition, subjects
performed both the imagined movement and visual attention tasks simultaneously in
response to left or right cues. Results from this third condition showed that subjects
could simultaneously produce SSVEP and ERD activity that should be adequate for
4 This chapter was originally written in 2008, and this sentence was true through 2009. However,
numerous groups began reporing hybrid BCI research in 2010.