Biomedical Engineering Reference
In-Depth Information
M
j
(
)
is hypothesized to express the communi-
cation capability (healthiness) of the brain tissue at the
j
th voxel location. This
hypothesis has been tested by applying the mean imaginary coherence (MIC)
mapping to various types of clinical data, and results positively confirming the validity
of the hypothesis have been obtained. Such investigations include the MIC mapping
for stroke-recovery patients [
21
], and patients with traumatic brain lesions [
22
]. In
these applications, mapping of
The mean imaginary coherence
f
can predict the degree of a patient's recovery
from stroke or brain injury. The MIC mapping has also been applied to MEG data
from patients with schizophrenia [
23
] and Alzheimer's disease [
24
], and the values
of
M
j
(
f
)
are found to be significantly correlated with patient symptom scores at
particular brain areas.
M
j
(
f
)
7.10 Numerical Examples
Computer simulation was performed to illustrate results of our arguments in this
chapter. A sensor alignment of the 275-sensor array from the Omega™ (VMS
Medtech, Coquitlam, Canada) neuromagnetometer was used. The coordinate sys-
tem and source-sensor configuration used in the computer simulation are depicted
0 cm) was assumed at the middle of the
whole-head sensor array, and three sources were assumed to exist on this plane.
Multiple-trial measurements were simulated, in which a total of 120 trials were
generated with each trial consisting of 600 time points. The data were assumed to
be collected with 2ms sampling. We first conducted numerical experiments with
=
(a)
(b)
0
1
1
0
1
0
1
1
0
1
0
1
1
0
1
100
200
300
400
500
600
0
100
200
300
400
500
600
time points
time points
Fig. 7.2
Examples of the time courses
a
for the alpha-band experiments and
b
for the gamma-band
experiments. The
top
,
middle
,and
bottom panels
, respectively, show the time courses for the first,
second, and third sources
