PMC2272302_01
Picture of the virtual street populated with 15 avatars and the tetraplegic subject in his
wheelchair in the middle of the multi-projection wall VR system. The subject
was wearing the electrode cap with one bipolar channel connected to the BCI
system (amplifier and laptop on the right side).
CIN2007-79642.001.jpg
PMC2272302_01_CIN2007-79642.001.jpg
fig1
West Sussex, UK) which surrounds the user with three back-projected active stereo screens (3 walls) and a front-projected screen on the floor (see Figure 1).
The task of
the participant was to go from avatar to avatar towards the end of the street
(outlined with a dashed line). The avatars were lined up and each avatar had
its invisible communication sphere (drawn as dotted lines here). The subject
had to stop within this sphere, not too close and not too far away from the
avatar.
CIN2007-79642.002.jpg
PMC2272302_01_CIN2007-79642.002.jpg
fig2
The used VE was a virtual street with shops on both sides and populated with 15 virtual characters (avatars), which were lined up along the street (see Figure 2,). Each avatar was surrounded by an invisible communication sphere (0.5-2.5 units) and the subject had to stop within this sphere (see Figure 2 and Figure 3(g)).
(a) Raw EEG
during periods of foot MI and rest. (b) Bandpass-filtered (15-19 Hz) EEG. (c),
(d) Power spectra of 2-second periods during rest (c) and foot MI (d). The
frequency band and the threshold are indicated. (e) Logarithmic band power time
course with threshold (TH). (f) Periods of moving and covered distance. The
contact with avatar 1 occurred at second 11.4 after a 1 second pause within the
communication sphere (because at second 8.9 the subject stopped shorter than
1-second). (g) Spatial placement of the avatars with corresponding
communication sphere and direction of walking. The communication sphere of
avatar 1:stopping range for the subject:is also marked with a
gray rectangle (f). (h) Spatial-temporal tracking data of the first four
avatars of three runs. The communication spheres of avatars are again indicated
with a gray rectangle. The time and position of the contact with the avatar are
marked with an "*".
In run 7, the third avatar was missed. (i) Picture sequence before, during, and
after the contact with avatar 1.
CIN2007-79642.003.jpg
PMC2272302_01_CIN2007-79642.003.jpg
fig3
Whenever the band power exceeded the threshold, a foot MI was detected (see Figures 3(a)-3(e)). Only during the time when the TH was exceeded (IC, foot MI detected), the subject moved forward (moving speed 1.25 units/second, see Figure 3(e)-3(f)). Each avatar was surrounded by an invisible communication sphere (0.5-2.5 units) and the subject had to stop within this sphere (see Figure 2 and Figure 3(g)). The avatar started talking to the subject, if he was standing still for one second within this sphere (see Figure 3(i)).