Information Technology Reference
In-Depth Information
Fig. 1.5
Five bandwidths are established for the varying control signal, which are associated to
the indices of an array of musical notes
subject is staring at this image and sends a command to generate the respective
melody. The SSVEP paradigm is interesting because the more the subject attends to
the
flashing image, the more prominent is the amplitude of the EEG component
corresponding to the brain
s response to this stimulus. This produces a varying
control signal, which is used to produce the melody and provide a visual feedback
to the user: the size of the image increases or decreases in function of this control
signal. In this way, we can steer the production of the notes by the intensity to
which one attends to the respective image. One can bring the index down by
looking away and bring the index up by staring at it again. Fine control of this
variation can be achieved with practice, e.g. to repeat a single note many times or
repeat a subgroup of notes. Each of the images could correspond to a distinct note
sequence, and so on. This scheme opens up many possibilities for music control.
The SSVEP-Music system has proved to be rather successful because one can
almost immediately produce musical notes with very little, or no training, simply by
looking intently at the different images. As one learns to modulate the extent to
which he or she is attending the images, more sophisticated musical control can be
achieved, as if learning to play a musical instrument: the more one practices, the
better one becomes at it.
Terster M trialled the system during a two-hour session. Being familiar with eye
gaze technology for her alternative communication system, Tester M grasped the
concept quickly and rapidly demonstrated her skills at playing the system with
minimal practice. She was able to vary the intensity of her gaze, thus changing the
amplitude of her EEG and vary the consequent melodic and dynamic output.
Personal correspondence with Tester M following this trial communicated that she
had enjoyed considerably using the system and that
'
“…
it was great to be in control
again
. This feedback is immensely gratifying and very encouraging. The possi-
bilities for applying the system within group settings are immediately apparent and
an exciting prospect for people with limited opportunities for participating as an
equal partner in a group.
”
