Brain-computer interface (BCI) is a relatively new field
of research that has been growing rapidly over the past 15
years [see 29 ]. A BCI system comprises a set of sensing
and signal-processing components that enables the acquisition
and analysis of brain activities in order to establish
a reliable, direct communication channel between
the brain and an external device such as a computer or a
neuroprosthesis system, etc. Figure 1 shows the basic design
and functioning blocks of a typical BCI system [see
29 ], which consists of 3 main parts: signal acquisition,
signal processing and applications. The brain signal is recorded
by electrodes placed on the scalp (noninvasive
BCI systems) or implanted in the brain (invasive BCI systems).
The signals obtained by these electrodes are generally
obscured by noises and other artifacts including
power line interference, electrode displacement, subject