Information Technology Reference
In-Depth Information
There are still a number of ways in which the averaging technique can be
improved and re
lling BCMI using the P300. What is
unique and exciting about this approach is that as it indicates the brain
ned for successful and ful
is cognitive
processes, it allows composers and performers to use knowledge of their own
unconscious in creative decisions, whilst simultaneously giving very accurate
results when users wish to indicate speci
'
c actions.
What follows are descriptions of P300 based BCMI systems that have been
prototyped as part of my continuing research at Goldsmiths. In almost all cases the
systems are created using bespoke software written in C++ for P300 ERP detection.
In addition, the systems described use raw EEG data only, from a range of electrode
locations. The type of EEG equipment used ranges from research grade to low-cost
consumer EEG. All the approaches here are reproducible, but it should be stressed
that the cheaper the equipment, the more challenging and creative the signal pro-
cessing approach needs to be in order to get reliable output. If in doubt, one should
use a professional research grade EEG system. Although multiple electrodes can
lead to better results, a single electrode placed at Cz is suf
cient for reasonable
results for the majority of the use cases detailed below.
3.4
The P300 Composer
As has already been discussed, P300 approaches can be very accurate even with a
high number of possible targets as long as the electrode quality, positioning and signal
conditioning is adequate. Providing these caveats have been met, the P300 Composer
is the simplest form of P300-based BCMI to create, and adequately demonstrates the
power and effectiveness of the approach. This method of creating a successful
visually controlled P300 BCI for music was
first described in the 2008 paper
“
Composing With Brainwaves: Minimal Trial P300b Recognition as an Indication of
Subjective Preference for the Control of a Musical Instrument
, (Grierson
2008
).
The method used (which is detailed below) was also speculated upon by David
Rosenboom as a potential future method for BCMI (Rosenboom
1976
).
The P300 composer is capable of allowing a motionless user the ability to create
a single monophonic pitched line from a range of possible pitches. The line itself
can have unlimited total duration, and can be composed of notes of
”
finite length,
and also gaps/musical rests. The system is now much simpler to build than in the
past as it can be produced by modifying the more-or-less standard P300 spellers
(see below) available in the public domain. Such paradigms are available in a
number of low-cost and free-to-use software libraries such as openVIBE
3
and
BCI2000.
4
Both these systems can be made to interoperate with OSC
5
making the
creation of P300 speller-based composer systems within reach of most researchers.
5
