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Abstract:
The P300 Event Related Potential (ERP) is reliably larger for
attended compared to ignored events. This characteristic suggests
that it could be useful in determining whether a subject was
attending to a recently presented event, and thus could allow users
to communicate their interest in events using only mental activity.
Brain Computer Interface (BCI) systems using this characteristic
have been demonstrated (Farwell and Donchin, 1988; Bayliss and
Ballard, 1998; Donchin et al., 2000). However, it is not known what
the optimal display parameters should be for a P300 based BCI. In
this study, subjects viewed an 8 x 8 display containing English
letters and other characters. Rows or columns of characters were
flashed, and subjects were asked to count flashes of a target
character while ignoring other events. Subjects participated in 6
conditions, with three different ISIs and two different approaches
to grouping flashed characters (single row or column vs. multiple
row or column flashes). P300 amplitude and area were larger in
response to attended vs. unattended flashes. In the multiple flash
condition, subjects' performance and P300 discriminability declined
at faster speeds, an effect less apparent in the single condition.
Other differences are discussed. We also present an improved
pattern recognition approach which can discriminate
attended/ignored events. Results suggest that improved brain
computer interfaces (BCIs) based on attentional differences via
brainwaves are feasible, and further elucidate the optimal display
parameters for such a system.
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