Systems, Man & Cybernetics - January 2016 - 8

Tongue Movements
During the Experiments

Lips

Channel Location

Fp1

Oral Cavity

Teeth

AF3

Tongue

F7

Contact Makes
Potential
Difference

F3

FC5
T7

Front (F, θ = 0)

Fp2
AFz

AF4
F4

Fz
FC1

FC6

FC2
Cz

C3

F8

T8

C4

Lips
Tongue

Left
(L, θ = -π /2)

Right
(R, θ = π /2)
Buccal
Wall
(a)

P7

CP2

CP1

CP5

Pz

P3

P4

P8

PO4

PO3
O1

CP6

Oz

O2

(b)

Figure 1. (a) If the tongue touches the inside of the cheek (buccal wall), a potential alteration is generated,

which is referred to as the gKP. this gKP has distinctive spatial patterns according to the position where the
tongue contacts the buccal wall. (b) the channel position for EEg recording during experiments.

horizontal tongue movements. To validate the specific
patterns of GKP, we recorded EEG signals during discrete and continuous tongue movements and investigated
their patterns. The EEG signals were recorded with the
Biosemi ActiveTwo system, and the electrode placement
is depicted in Figure 1(b). The signals were sampled at a
frequency of 2048 Hz and low-pass filtered with a cutoff
frequency at 4 Hz by a Butterworth filter to remove highfrequency oscillations.
In the first phase, we recorded the signals for discrete
tongue movements for 12 s. For the experiment, three cues
were assigned to the left (L, touching inside of the left
cheek), front (F, touching lips on the front side), and right
(R, touching inside of the right cheek) as represented in
Figure 1(a). We showed a sequence of the cues (F-L-F-R-
F-L) to a subject, and the subject moved his tongue in
accordance with the cues. The represented cues and
recorded signal were plotted in Figure 2.
The results showed that, when the tongue moved to the
right side (from L to F in 4 s, and F to R in 6 s), the potential
levels in electrode T8 located in the right hemisphere
decreased while the potential levels in T7 located in the
left hemisphere increased. On the other hand, when the
tongue moved back to the left side (from R to F in 8 s and
from F to L in 10 s), the potentials recorded in T8
increased, but the potentials recorded in T7 decreased.
Fp1 and Fp2 showed similar patterns as the potential
8

IEEE SyStEmS, man, & CybErnEtICS magazInE Janu ar y 2016

changes in T7 and T8, but the magnitudes of the changes
were smaller than that observed in T7 and T8.
In the second phase, in the time window from 12 to 31 s,
the signals for continuous tongue movements were recorded. Instead of the character cues assigned to the three
positions, we showed a pointer cue that moved along a horizontal line on the screen. The cue, which appeared at 12 s
on the left side, continuously moved to the right side for 4 s
and stopped for 1 s. Then, it moved back to the left side for
4 s and stopped for 1 s. This movement was repeated again
from 22 to 31 s. The subject was asked to move his tongue
in the direction where the cue was located while
maintaining contact between the tongue and the buccal
wall. This action is similar to that of licking the lips slowly
in horizontal directions.
When the tongue was moving from the left side to the
right side, the signal in T8 continuously decreased while
the signal in T7 increased in a similar continuous manner. On the other hand, when the tongue was moving to
the left side, the signal in T8 increased while the signal in
T7 decreased. The signals in Fp1 shared similar increasing or decreasing patterns with T7 while the signals in
Fp2 and T8 shared similar patterns. From the signals
recorded during the discrete and continuous tongue
movements, we observed that, when the negatively
charged tongue moved in the horizontal direction, the
potentials on the electrodes in the left and right



Table of Contents for the Digital Edition of Systems, Man & Cybernetics - January 2016

Systems, Man & Cybernetics - January 2016 - Cover1
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Systems, Man & Cybernetics - January 2016 - Cover3
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