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source location. The magnitude coherence image, imaginary coherence image, and
corrected imaginary coherence image are respectively shown in Fig.
7.3
b-d.
In the magnitude coherence image (Fig.
7.3
b), the seed blur dominates and
obscures the other sources. On the contrary, in the imaginary coherence image
(Fig.
7.3
c), and in the corrected imaginary coherence image (
7.3
d), the intensity
of the seed blur is much reduced and the two sources that interact with the second
source can clearly be observed. Also, the imaginary and the corrected imaginary
coherence images are very similar, because the magnitude coherence is as small as
0.26-0.35 in this computer simulation.
We next implemented the method described in Sect.
7.6.4
in which a single rep-
resentative voxel time course is not computed, but instead, the canonical coher-
ence is directly computed by using multiple voxel time courses. The image of
canonical imaginary coherence
ˈ
I
in Eq. (
7.83
) is shown in Fig.
7.4
a. The image
of mutual-information-based canonical imaginary coherence,
ˈ
I
in Eq. (
7.85
)is
shown in Fig.
7.4
b. The canonical magnitude coherence
in Eq. (
7.66
)isshown
in Fig.
7.4
c. An image of mutual-information-based canonical magnitude coherence
|
ˈ
|
(a)
(b)
14
13
12
11
10
9
8
7
6
6
4
2
0
2
4
6
6
4
2
0
2
4
6
y (cm)
y (cm)
(c)
(d)
14
13
12
11
10
9
8
7
6
6
4
2
0
2
4
6
6
4
2
0
2
4
6
y (cm)
y (cm)
Fig. 7.4
Results of imaging canonical coherence on the plane
x
=
0cm.
a
Image of canonical
imaginary coherence
I
in Eq. (
7.83
). The
asterisk
shows the location of the seed voxel.
b
Image of
mutual-information-based canonical imaginary coherence,
ˈ
ˈ
I
in Eq. (
7.85
).
c
Image of canonical
magnitude coherence
|
ˈ
|
in Eq. (
7.66
).
d
Image of mutual-information-based canonical magnitude
|
ˈ
|
coherence
in Eq. (
7.68
)
