U.S. patent application number 13/602703 was filed with the patent office on 2013-10-10 for electroencephalogram analysis apparatus, electroencephalogram analysis program, and electroencephalogram analysis method.
This patent application is currently assigned to SONY CORPORATION. The applicant listed for this patent is Yusaku Nakashima, Masaki Nishida, Takashi Tomita. Invention is credited to Yusaku Nakashima, Masaki Nishida, Takashi Tomita.
Application Number | 20130267866 13/602703 |
Document ID | / |
Family ID | 49292869 |
Filed Date | 2013-10-10 |
United States Patent
Application |
20130267866 |
Kind Code |
A1 |
Nakashima; Yusaku ; et
al. |
October 10, 2013 |
ELECTROENCEPHALOGRAM ANALYSIS APPARATUS, ELECTROENCEPHALOGRAM
ANALYSIS PROGRAM, AND ELECTROENCEPHALOGRAM ANALYSIS METHOD
Abstract
An electroencephalogram analysis apparatus includes an
electroencephalogram acquisition part and a comparison part. The
electroencephalogram acquisition part is configured to acquire a
first electroencephalogram measured at a first region on a head of
a test subject and a second electroencephalogram measured at a
second region positioned behind the first region on the head of the
test subject. The comparison part is configured to compare a power
of the first electroencephalogram in a specific frequency band with
a power of the second encephalogram in the specific frequency
band.
Inventors: |
Nakashima; Yusaku; (Tokyo,
JP) ; Tomita; Takashi; (Kanagawa, JP) ;
Nishida; Masaki; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nakashima; Yusaku
Tomita; Takashi
Nishida; Masaki |
Tokyo
Kanagawa
Tokyo |
|
JP
JP
JP |
|
|
Assignee: |
SONY CORPORATION
Tokyo
JP
|
Family ID: |
49292869 |
Appl. No.: |
13/602703 |
Filed: |
September 4, 2012 |
Current U.S.
Class: |
600/544 |
Current CPC
Class: |
A61B 5/0476 20130101;
A61B 5/4812 20130101; A61B 5/0488 20130101; A61B 5/04012 20130101;
A61B 5/165 20130101; A61B 5/048 20130101 |
Class at
Publication: |
600/544 |
International
Class: |
A61B 5/048 20060101
A61B005/048 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 5, 2012 |
JP |
2012-086588 |
Claims
1. An electroencephalogram analysis apparatus, comprising: an
electroencephalogram acquisition part configured to acquire a first
electroencephalogram measured at a first region on a head of a test
subject and a second electroencephalogram measured at a second
region positioned behind the first region on the head of the test
subject; and a comparison part configured to compare a power of the
first electroencephalogram in a specific frequency band with a
power of the second encephalogram in the specific frequency
band.
2. The electroencephalogram analysis apparatus according to claim
1, wherein the first region is a prefrontal region, and the second
region is a frontal region.
3. The electroencephalogram analysis apparatus according to claim
2, wherein the first region is an Fp region defined based on the
International 10-20 system, and the second region is an F region
defined based on the International 10-20 system.
4. The electroencephalogram analysis apparatus according to claim
1, wherein the specific frequency band is a frequency band of sleep
spindles.
5. The electroencephalogram analysis apparatus according to claim
4, wherein the specific frequency band is a frequency band of slow
sleep spindles.
6. The electroencephalogram analysis apparatus according to claim
5, wherein the frequency band of the slow sleep spindles is greater
than or equal to 10.5 Hz and less than or equal to 12.5 Hz.
7. The electroencephalogram analysis apparatus according to claim
1, further comprising a stage discrimination part configured to
discriminate a sleep stage of the test subject, wherein the first
electroencephalogram is an electroencephalogram of any of sleep
stages 2 to 4 measured at the first region, and the second
electroencephalogram is an electroencephalogram of any of the sleep
stages 2 to 4 measured at the second region.
8. The electroencephalogram analysis apparatus according to claim
1, wherein the comparison part transforms the first
electroencephalogram into a frequency component to generate a first
electroencephalogram spectrum, transforms the second
electroencephalogram into a frequency component to generate a
second electroencephalogram spectrum, and compares an integral
value of the first electroencephalogram spectrum in the specific
frequency band with an integral value of the second
electroencephalogram spectrum in the specific frequency band.
9. The electroencephalogram analysis apparatus according to claim
1, further comprising a diagnosis part configured to diagnose
whether the test subject is in a mood disorder state based on a
comparison result of the comparison part.
10. The electroencephalogram analysis apparatus according to claim
9, wherein the diagnosis part diagnoses that the test subject is in
the mood disorder state when the power of the first
electroencephalogram in the specific frequency band is greater than
the power of the second electroencephalogram in the specific
frequency band.
11. An electroencephalogram analysis program that causes a computer
to function as: an electroencephalogram acquisition part configured
to acquire a first electroencephalogram measured at a first region
on a head of a test subject and a second electroencephalogram
measured at a second region positioned behind the first region on
the head of the test subject; and a comparison part configured to
compare a power of the first electroencephalogram in a specific
frequency band with a power of the second encephalogram in the
specific frequency band.
12. An electroencephalogram analysis method, comprising: acquiring
a first electroencephalogram measured at a first region on a head
of a test subject and a second electroencephalogram measured at a
second region positioned behind the first region on the head of the
test subject; and comparing a power of the first
electroencephalogram in a specific frequency band with a power of
the second encephalogram in the specific frequency band.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] The present application claims priority to Japanese Priority
Patent Application JP 2012-086588 filed in the Japan Patent Office
on Apr. 5, 2012, the entire content of which is hereby incorporated
by reference.
BACKGROUND
[0002] The present disclosure relates to an electroencephalogram
analysis apparatus, an electroencephalogram analysis program, and
an electroencephalogram analysis method for analyzing
electroencephalograms measured at the head of a test subject.
[0003] Mood disorders such as depression, schizophrenia, and
bipolar disorder (symptom where a depressed state and a manic state
alternately appear) cannot be diagnosed from the physical symptoms
of patients. Therefore, clinical methods such as asking patients
about their conditions are generally conducted to diagnose such
mood disorders. Meanwhile, it is difficult for patients to judge
such mood disorders by themselves, and the patients are thus likely
to lose opportunities to consult doctors at the early stages of the
disorders. It is assumed that the availability of any clear
barometers indicating such mood disorders facilitates the judgement
of the mood disorders, thus making it possible for patients to
judge the mood disorders by themselves.
[0004] In recent years, there have been developed technologies for
diagnosing mood disorders such as depression based on
electroencephalograms (electrical activities of the brain of a
human). For example, Japanese Patent Application Laid-open No.
2009-518076 discloses a "system and method of analyzing and
evaluating depression and other mood disorders using
electroencephalogram (EEG) measurement values." The system allows
the evaluation of the mood disorders based on the results of
electroencephalograms measured when test subjects are in a wakeful
state (i.e. in a non-sleep state), more specifically, based on the
asymmetry of right and left front qEEGs (quantitative
electroencephalograms).
SUMMARY
[0005] The system described in Japanese Patent Application
Laid-open No. 2009-518076 is used to evaluate the mood disorders
based on the results of the electroencephalograms measured when the
patients are in the wakeful state. Therefore, the patients have to
take time for measuring the electroencephalograms in their daily
lives and may be forced to bear the burden of measuring the
electroencephalograms. Meanwhile, the present inventors have found
characteristics indicating the mood disorders in the
electroencephalograms measured during sleep states and achieved a
method of evaluating the mood disorders using the
characteristics.
[0006] The present disclosure has been made in view of the above
circumstances, and it is therefore desirable to provide an
electroencephalogram analysis apparatus, an electroencephalogram
analysis program, and an electroencephalogram analysis method
capable of diagnosing mood disorders based on the
electroencephalograms of a test subject.
[0007] According to an embodiment of the present disclosure, there
is provided an electroencephalogram analysis apparatus including an
electroencephalogram acquisition part and a comparison part.
[0008] The electroencephalogram acquisition part is configured to
acquire a first electroencephalogram measured at a first region on
a head of a test subject and a second electroencephalogram measured
at a second region positioned behind the first region on the head
of the test subject.
[0009] The comparison part is configured to compare a power of the
first electroencephalogram in a specific frequency band with a
power of the second encephalogram in the specific frequency
band.
[0010] The present inventors have found a difference in the
distribution of the powers of the electroencephalograms in the
specific frequency band, particularly on the front and rear sides
of the head, between a mood disorder state and a normal state.
Accordingly, it is possible to diagnose whether the test subject is
in the mood disorder state by the comparison between the power of
the electroencephalogram in the specific frequency band measured at
the first region and that of the electroencephalogram in the
specific frequency band measured at the second region, the first
region and the second region being positioned on the front and rear
sides of the head of the test subject, respectively. In other
words, the electroencephalogram analysis apparatus with the above
configuration makes it possible to diagnose whether the test
subject is in the mood disorder state.
[0011] In the electroencephalogram analysis apparatus, the first
region may be a prefrontal region, and the second region may be a
frontal region.
[0012] It has been found as the distribution of the powers of the
electroencephalograms in the specific frequency band that the power
of the electroencephalogram on the front side (frontal region) of
the head becomes the greatest when the test subject is in the
normal state and that the power of the electroencephalogram on the
further front side (prefrontal region) of the head becomes the
greatest when the test subject is in the mood disorder state.
Accordingly, it is possible to more clearly detect the difference
in the distribution of the powers between the mood disorder state
and the normal state by setting the prefrontal region as the first
region and the frontal region as the second region.
[0013] The first region may be an Fp region defined based on the
International 10-20 system, and the second region may be an F
region defined based on the International 10-20 system.
[0014] The prefrontal region corresponds to the Fp region (Fp1,
Fpz, or Fp2) based on the definition of the International 10-20
system, and the frontal region corresponds to the F region (Fz or
F1 to F9) based on the definition of the International 10-20
system.
[0015] The specific frequency band is a frequency band of sleep
spindles.
[0016] It has been confirmed that the difference in the
distribution of the powers occurs at least in the frequency band
(generally, greater than or equal to 10.5 Hz and less than or equal
to 16 Hz) of the sleep spindles. Accordingly, by setting the
frequency band of the sleep spindles as the specific frequency
band, it is possible to diagnose whether the test subject is in the
mood disorder state based on the electroencephalograms measured at
the first region and the second region.
[0017] The sleep spindles are classified into slow sleep spindles
and fast sleep spindles. The difference in the distribution of the
powers between the mood disorder state and the normal state can be
notably seen in the slow sleep spindles. Therefore, it is possible
to diagnose whether the test subject is in the mood disorder state
by setting the frequency band of the slow sleep spindles as the
specific frequency band.
[0018] The frequency band of the slow sleep spindles may be greater
than or equal to 10.5 Hz and less than or equal to 12.5 Hz.
[0019] The frequency band of the slow sleep spindles is generally
greater than or equal to 10.5 Hz and less than or equal to 12.5 Hz
in the field of electroencephalogram measurement.
[0020] The electroencephalogram analysis apparatus may further
include a stage discrimination part configured to discriminate a
sleep stage of the test subject. The first electroencephalogram may
be an electroencephalogram of any of sleep stages 2 to 4 measured
at the first region, and the second electroencephalogram may be an
electroencephalogram of any of the sleep stages 2 to 4 measured at
the second region.
[0021] Electroencephalograms (such as alpha waves) occurring when
the test subject is not in a sleep state may overlap with the
specific frequency, resulting in a difficulty in diagnosing whether
the test subject is in the mood disorder state. According to the
configuration, the stage discrimination part discriminates the
sleep stage of the test subject. Therefore, it is possible to
diagnose whether the test subject is in the mood disorder state
based on the electroencephalograms occurring when the test subject
is reliably in the sleep state (any of stages 2 to 4). Note that
the stage discrimination part can discriminate the sleep stage
using various biological signals such as an electroencephalogram,
an electrooculogram, and an electromyogram of the test subject.
[0022] The comparison part may transform the first
electroencephalogram into a frequency component to generate a first
electroencephalogram spectrum, transform the second
electroencephalogram into a frequency component to generate a
second electroencephalogram spectrum, and compare an integral value
of the first electroencephalogram spectrum in the specific
frequency band with an integral value of the second
electroencephalogram spectrum in the specific frequency band.
[0023] It is possible to compare the power of the first
electroencephalogram with that of the second electroencephalogram
in the specific frequency band by comparing the integral value of
the first electroencephalogram spectrum with that of the second
electroencephalogram spectrum in the specific frequency band, the
first electroencephalogram spectrum and the second
electroencephalogram spectrum being obtained by transforming the
first electroencephalogram and the second electroencephalogram into
frequency components, respectively.
[0024] The electroencephalogram analysis apparatus may further
include a diagnosis part configured to diagnose whether the test
subject is in a mood disorder state based on a comparison result of
the comparison part.
[0025] The diagnosis part may diagnose that the test subject is in
the mood disorder state when the power of the first
electroencephalogram in the specific frequency band is greater than
that of the second electroencephalogram in the specific frequency
band.
[0026] An electroencephalogram analysis program according to
another embodiment of the present disclosure causes a computer to
function as an electroencephalogram acquisition part and a
comparison part.
[0027] The electroencephalogram acquisition part is configured to
acquire a first electroencephalogram measured at a first region on
a head of a test subject and a second electroencephalogram measured
at a second region positioned behind the first region on the head
of the test subject.
[0028] The comparison part is configured to compare a power of the
first electroencephalogram in a specific frequency band with a
power of the second encephalogram in the specific frequency
band.
[0029] An electroencephalogram analysis method according to still
another embodiment of the present disclosure includes: acquiring a
first electroencephalogram measured at a first region on a head of
a test subject and a second electroencephalogram measured at a
second region positioned behind the first region on the head of the
test subject; and comparing a power of the first
electroencephalogram in a specific frequency band with a power of
the second encephalogram in the specific frequency band.
[0030] As described above, according to the embodiments of the
present disclosure, it is possible to provide an
electroencephalogram analysis apparatus, an electroencephalogram
analysis program, and an electroencephalogram analysis method
capable of diagnosing mood disorders based on the
electroencephalograms of a test subject.
[0031] These and other objects, features and advantages of the
present disclosure will become more apparent in light of the
following detailed description of best mode embodiments thereof, as
illustrated in the accompanying drawings.
[0032] Additional features and advantages are described herein, and
will be apparent from the following Detailed Description and the
figures.
BRIEF DESCRIPTION OF THE FIGURES
[0033] FIG. 1 is a schematic view showing an electroencephalogram
analysis apparatus according to an embodiment of the present
disclosure;
[0034] FIG. 2 is a schematic view of the measurement positions of
electroencephalograms defined based on the International 10-20
system;
[0035] FIG. 3 is a flowchart showing the operations of the
electroencephalogram analysis apparatus according to the embodiment
of the present disclosure;
[0036] FIG. 4 is a table showing an example of the method of
discriminating sleep stages;
[0037] FIGS. 5A and 5B are graphs showing the examples of
electroencephalogram spectrums generated by the
electroencephalogram analysis apparatus according to the embodiment
of the present disclosure;
[0038] FIGS. 6A and 6B are graphs showing the examples of
electroencephalogram spectrums generated by the
electroencephalogram analysis apparatus according to the embodiment
of the present disclosure;
[0039] FIGS. 7A and 7B are graphs respectively showing the powers
of the electroencephalograms (slow sleep spindles) measured at the
measurement regions when a test subject is in a mood disorder state
and a normal state;
[0040] FIGS. 8A and 8B are schematic views respectively showing the
distribution of the powers of the electroencephalograms (slow sleep
spindles) measured at the measurement regions when the test subject
is in the mood disorder state and the normal state;
[0041] FIGS. 9A and 9B are graphs respectively showing the
distribution of the powers of the electroencephalograms (fast sleep
spindles) measured at the measurement regions when the test subject
is in the mood disorder state and the normal state; and
[0042] FIGS. 10A and 10B are schematic views respectively showing
the distribution of the powers of the electroencephalograms (fast
sleep spindles) measured at the measurement regions when the test
subject is in the mood disorder state and the normal state.
DETAILED DESCRIPTION
[0043] (Configuration of Electroencephalogram Analysis
Apparatus)
[0044] An electroencephalogram analysis apparatus according to an
embodiment will be described. FIG. 1 is a schematic view showing
the configuration of the electroencephalogram analysis apparatus
100. As shown in FIG. 1, the electroencephalogram analysis
apparatus 100 includes an analysis unit 110 and an
electroencephalograph 120. The analysis unit 110 is, for example,
an information processing apparatus and connected to the
electroencephalograph 120 to analyze electroencephalograms measured
by the electroencephalograph 120. The analysis unit 110 and the
electroencephalograph 120 may be integrated with each other or may
be separated from each other. Further, FIG. 1 shows the head H of a
test subject.
[0045] The electroencephalograph 120 includes a first measurement
electrode 121, a second measurement electrode 122, and an
electroencephalogram measurement part 123. The first measurement
electrode 121 is connected to a "first region" on the head H to
detect the electroencephalogram (EEG) of the test subject at the
first region. The second measurement electrode 122 is connected to
a "second region" on the head H to detect the electroencephalogram
of the test subject at the second region. Note that the
electroencephalograph 120 may further include, besides the first
measurement electrode 121 and the second measurement electrode 122,
a measurement electrode that detects the electroencephalogram.
[0046] FIG. 2 is a schematic view for explaining the first region
and the second region. Note that FIG. 2 shows the positions of
measurement electrodes based on the International 10-20 system
where the measurement positions of electroencephalograms are
defined.
[0047] As will be described in detail below, the first region to
which the first measurement electrode 121 is connected and the
second region to which the second measurement electrode 122 is
connected can be arranged such that the second region is positioned
behind the first region in the head H of the test subject. More
desirably, the first region can be a prefrontal region, and the
prefrontal region corresponds to the Fp region (Fp1, Fpz, or Fp2)
based on the International 10-20 system shown in FIG. 2.
[0048] Further, the second region can be a frontal region, and the
frontal region corresponds to the F region (Fz or F1 to F9) based
on the International 10-20 system shown in FIG. 2. Note that the
first region and the second region are not necessarily the regions
defined based on the International 10-20 system and only need to be
regions at which a difference in the distribution of the powers of
the electroencephalograms, which will be described below, can be
measured.
[0049] The electroencephalogram measurement part 123 is connected
to the first measurement electrode 121 and the second measurement
electrode 122, measures the electroencephalograms detected by the
first measurement electrode 121 and the second measurement
electrode 122, and outputs the measured electroencephalograms to
the analysis unit 110 in a wired or wireless manner. Hereinafter,
the electroencephalogram measured by the first measurement
electrode 121 at the first region will be referred to as a "first
electroencephalogram," while the electroencephalogram measured by
the second measurement electrode 122 at the second region will be
referred to as a "second electroencephalogram." Note that the
electroencephalograph 120 can further include a standard electrode
(neutral electrode) that detects a standard potential of the
electroencephalogram, a reference electrode that detects the
contact resistance between the first and second measurement
electrodes 121 and 122 and the front surface of the head H, or the
like.
[0050] The analysis unit 110 includes an electroencephalogram
acquisition part 111, a stage discrimination part 112, a comparison
part 113, and a diagnosis part 114. These constituent parts can be
functional parts implemented by the cooperation between the
software and the hardware of the analysis unit 110 and may also be
mounted on a network. The electroencephalogram acquisition part 111
is connected to the stage discrimination part 112 and the
comparison part 113, and the comparison part 113 is connected to
the diagnosis part 114. The stage discrimination part 112 is
connected to the comparison part 113.
[0051] The electroencephalogram acquisition part 111 acquires the
first electroencephalogram and the second electroencephalogram
output from the electroencephalogram measurement part 123 of the
electroencephalograph 120 and supplies the acquired first and
second electroencephalograms to the stage discrimination part 112
and the comparison part 113.
[0052] The stage discrimination part 112 discriminates the "sleep
stages" (see FIG. 4) of the test subject based on the first
electroencephalogram and the second electroencephalogram supplied
from the electroencephalogram acquisition part 111 or based on
other measurement data on the test subject. In the sleep stages,
the state of the test subject is classified into five stages 1 to 5
with a wakeful state as the first stage depending on the degree of
the activity of the brain of the test subject. The sleep stages
will be described in detail below. The stage discrimination part
112 supplies the discriminated sleep stage to the comparison part
113.
[0053] The comparison part 113 compares the power of the first
electroencephalogram with that of the second electroencephalogram
in a specific frequency band. The comparison part 113 can perform
the comparison when the sleep stage of the test subject
discriminated by the stage discrimination part 112 is any of the
sleep states (stages 2 to 4). As the specific frequency band used
by the comparison part 113 for the comparison, a frequency band
(generally 10.5 Hz to 12.5 Hz) of sleep spindles, desirably, slow
sleep spindles is available. The comparison part 113 supplies the
comparison result to the diagnosis part 114.
[0054] Based on the comparison result of the comparison part 113,
the diagnosis part 114 diagnoses whether the test subject has a
mood disorder. Specifically, if the power of the first
electroencephalogram is greater than that of the second
electroencephalogram in the specific frequency band, the diagnosis
part 114 can diagnose that the test subject is in the mood disorder
state. On the other hand, if the power of the second
electroencephalogram is greater than that of the first
electroencephalogram in the specific frequency band, the diagnosis
part 114 can diagnose that the test subject is not in the mood
disorder state (the test subject is in a normal state). The
diagnosis part 114 can display the diagnosis result on a display
(not shown) or the like. Note that the mood disorder state refers
to an abnormal mental state such as depression, schizophrenia, and
bipolar disorder (symptom where a depressed state and a manic state
alternately appear).
[0055] (Operations of Electroencephalogram Analysis Apparatus)
[0056] The operations of the electroencephalogram analysis
apparatus 100 will be described. FIG. 3 is a flowchart showing the
operations of the electroencephalogram analysis apparatus 100.
[0057] The electroencephalogram acquisition part 111 acquires the
first electroencephalogram and the second electroencephalogram from
the electroencephalogram measurement part 123 (Step 1). The
electroencephalogram acquisition part 111 may acquire the first
electroencephalogram and the second electroencephalogram from the
electroencephalogram measurement part 123 as occasion demands, or
is capable of acquiring the first electroencephalogram and the
second electroencephalogram measured by the electroencephalogram
measurement part 123 and recorded on a recording part (not shown)
for a predetermined period of time. The electroencephalogram
acquisition part 111 supplies the first electroencephalogram and
the second electroencephalogram thus acquired to the stage
discrimination part 112 and the comparison part 113.
[0058] Next, the stage discrimination part 112 discriminates the
sleep stage of the test subject (Step 2). FIG. 4 is a table showing
the respective sleep stages and an example of the method of
discriminating the sleep stages. As shown in FIG. 4, the sleep
state of the test subject can be classified into any of the
non-sleep stage (WAKE), the REM sleep stage (REM), and the non-REM
sleep stage depending on the state of the activity of the brain. In
the case of the non-REM sleep stage, the sleep state of the test
subject can further be classified into any of the stage 1
(hypnagogic state), the stage 2 (light sleep state), the stage 3
(moderate sleep state), and the stage 4 (deep sleep state)
depending on the depth of the sleep of the test subject.
[0059] The stage discrimination part 112 discriminates which of the
sleep stages the sleep state of the test subject is classified
into. The stage discrimination part 112 may discriminate the sleep
stages using the first electroencephalogram and the second
electroencephalogram supplied from the electroencephalogram
acquisition part 111, or may discriminate the sleep stages using
other biological signals obtained by measuring the test subject. As
the biological signals, an electrooculogram (EGO), an
electromyogram (EMG), or the like is available. The stage
discrimination part 112 supplies the discriminated sleep stage to
the comparison part 113.
[0060] Then, the comparison part 113 compares the power of the
first electroencephalogram with that of the second
electroencephalogram in the specific frequency band (Step 3). Here,
the comparison part 113 can perform the comparison only when the
sleep stage discriminated by the stage discrimination part 112 is
any of the sleep stages 2 to 4. This is because, when the test
subject is in the incomplete sleep states (WAKE, REM, and stage 1),
electroencephalograms (such as alpha waves) whose frequency band
overlaps with the specific frequency band may occur, i.e., the
diagnosis of the diagnosis part 114 (that will be described below)
may be inhibited.
[0061] The comparison part 113 can perform the comparison by
transforming (frequency-transforming) the first
electroencephalogram and the second electroencephalogram into
frequency components. Hereinafter, the frequency component
transformed from the first electroencephalogram will be referred to
as a first electroencephalogram spectrum, while the frequency
component transformed from the second electroencephalogram will be
referred to as a second electroencephalogram spectrum. FIGS. 5A and
5B are graphs showing the examples of the first
electroencephalogram spectrum and the second electroencephalogram
spectrum, respectively. The comparison part 113 can
frequency-transform the first electroencephalogram and the second
electroencephalogram according to any method, for example, a fast
Fourier transform, a wavelet transform, or the like.
[0062] Using the first electroencephalogram spectrum and the second
electroencephalogram spectrum, the comparison part 113 can compare
the power of the first electroencephalogram with that of the second
electroencephalogram in the specific frequency band. Specifically,
the comparison part 113 can compare the integral value of the first
electroencephalogram spectrum in the specific frequency band (here,
greater than or equal to 10.5 Hz and less than or equal to 12.5 Hz)
with that of the second electroencephalogram spectrum in the
specific frequency band. In FIGS. 5A and 5B, the integral values of
the first electroencephalogram spectrum and the second
electroencephalogram spectrum in the specific frequency band
(greater than or equal to 10.5 Hz and less than or equal to 12.5
Hz) are indicated as the areas of shaded regions.
[0063] As the specific frequency band, a frequency band (greater
than or equal to 10.5 Hz and less than or equal to 16 Hz) of sleep
spindles can be set. Further, the sleep spindles can be classified
into fast sleep spindles (greater than or equal to 12.5 Hz and less
than or equal to 16 Hz) and slow sleep spindles (greater than or
equal to 10.5 Hz and less than or equal to 12.5 Hz). However, the
frequency band of the slow sleep spindles (that will be described
below) is particularly desirable as the specific frequency band.
Note that the specific numerical values (such as 10.5 Hz)
exemplified here as the frequency band are the numerical values
generally used in the field of electroencephalogram measurement,
and the specific frequency band is not necessarily limited to the
values.
[0064] As shown in FIGS. 5A and 5B, the comparison part 113 can
compare the power of the first electroencephalogram with that of
the second electroencephalogram in the specific frequency band by
comparing the size of the integral value of the first
electroencephalogram spectrum with that of the second
electroencephalogram spectrum in the specific frequency band.
Further, the comparison part 113 does not necessarily use the
electroencephalogram spectrums and is capable of comparing the
power of the first electroencephalogram with that of the second
electroencephalogram in the specific frequency band according to
other methods. The comparison part 113 supplies the comparison
result, i.e., the relationship between the power of the first
electroencephalogram and that of the second electroencephalogram in
the specific frequency band to the diagnosis part 114.
[0065] The diagnosis part 114 diagnoses whether the test subject is
in the mood disorder state based on the comparison result of the
comparison part 113 (Step 4). The diagnosis part 114 can diagnose
that the test subject is in the mood disorder state if the
comparison result of the comparison part 113 shows that the power
of the first electroencephalogram is greater than that of the
second electroencephalogram in the specific frequency band. On the
other hand, the diagnosis part 114 can diagnose that the test
subject is not in the mood disorder state (the test subject is in
the normal state) if the comparison result of the comparison part
113 shows that the power of the first electroencephalogram is less
than that of the second electroencephalogram in the specific
frequency band. For example, because FIGS. 5A and 5B show a case
where the power of the first electroencephalogram (the area of the
shaded region in FIG. 5A) is greater than that of the second
electroencephalogram (the area of the shaded region in FIG. 5B) in
the specific frequency band (greater than or equal to 10.5 Hz and
less than or equal to 12.5 Hz), the diagnosis part 114 can diagnose
that the test subject is in the mood disorder state.
[0066] On the other hand, FIGS. 6A and 6B are graphs showing the
examples of the first electroencephalogram spectrum acquired at the
first region and the second electroencephalogram spectrum acquired
at the second region, respectively. Because the power of the first
electroencephalogram (the area of the shaded region in FIG. 6A) is
less than that of the second electroencephalogram (the area of the
shaded region in FIG. 6B) in the specific frequency band (greater
than or equal to 10.5 Hz and less than or equal to 12.5 Hz), the
diagnosis part 114 can diagnose that the test subject is in the
normal state.
[0067] (Principle of Diagnosis)
[0068] The principle by which the diagnosis part 114 can perform
the above diagnosis will be described. FIGS. 7A and 7B are graphs
showing the powers of the slow sleep spindles (greater than or
equal to 10.5 Hz and less than or equal to 12.5 Hz) measured at the
respective regions of the head of the test subject. FIG. 7A shows
the powers of the slow sleep spindles obtained when the test
subject in the mood disorder state is measured, while FIG. 7B shows
the powers of the slow sleep spindles obtained when the test
subject in the normal state is measured. The graphs shown in FIGS.
7A and 7B are obtained in such a manner that the respective regions
based on the International 10-20 system shown in FIG. 2 are
measured. The comparison between these graphs shows that the power
of the slow sleep spindle at the prefrontal region (the Fp region)
is the greatest in the graph shown in FIG. 7A, while the power of
the slow sleep spindle at the frontal region (the F region) is the
greatest in the graph shown in FIG. 7B.
[0069] FIGS. 8A and 8B each display the distribution of the powers
of the slow sleep spindles measured at the respective regions so as
to be reflected in the shape of the head of the test subject (the
upper side of the head in each of FIGS. 8A and 8B represents the
front side of the test subject). FIG. 8A shows the distribution of
the powers of the slow sleep spindles measured when the test
subject is in the mood disorder state, while FIG. 8B shows the
distribution of the powers of the slow sleep spindles measured when
the test subject is in the normal state. In FIGS. 8A and 8B, the
greater the powers of the slow sleep spindles, the darker the
regions are colorized. It is found that, when the test subject is
in the mood disorder state, the regions of the greater powers of
the slow sleep spindles exist on the front side of the head (near
the prefrontal region) as shown in FIG. 8A. On the other hand, it
is found that, when the test subject is in the normal state, the
regions of the greater powers of the slow sleep spindles exist on a
further rear side of the head (near the frontal region) as shown in
FIG. 8B.
[0070] Accordingly, it is possible to diagnose whether the test
subject is in the mood disorder state by the comparison of the
powers of the electroencephalograms between the first region (for
example, the prefrontal region) and the second region (for example,
the frontal region) positioned on the further rear side of the head
of the test subject in the frequency band of the slow sleep
spindles. As shown in FIGS. 7A and 8A, when the test subject is in
the mood disorder state, the powers of the electroencephalograms on
the front side of the head become greater. Accordingly, when the
power (the area of the shaded region) of the electroencephalogram
of the first region (first electroencephalogram) shown in FIG. 5A
is compared with that (the area of the shaded region) of the
electroencephalogram of the second region (second
electroencephalogram) shown in FIG. 5B, it is found that the power
of the electroencephalogram of the first region (FIG. 5A) is
greater than that of the electroencephalogram of the second region
(FIG. 5B).
[0071] On the other hand, as shown in FIGS. 7B and 8B, when the
power of the electroencephalogram of the first region (first
electroencephalogram) is compared with that of the
electroencephalogram of the second region (second
electroencephalogram) as for the test subject in the normal state,
it is found that the power of the second electroencephalogram is
greater than that of the first electroencephalogram. As shown in
FIGS. 7B and 8B, when the test subject is in the normal state, the
powers of the electroencephalograms become greater near the center
of the head. Accordingly, when the power (the area of the shaded
region) of the electroencephalogram of the first region (first
electroencephalogram) shown in FIG. 6A is compared with that (the
area of the shaded region) of the electroencephalogram of the
second region (second electroencephalogram) shown in FIG. 6B, it is
found that the power of the electroencephalogram of the second
region (FIG. 6B) is greater than that of the electroencephalogram
of the first region (FIG. 6A).
[0072] As described above, using the difference in the distribution
of the powers of the slow sleep spindles between the mood disorder
state and the normal state, it is possible to diagnose whether the
test subject is in the mood disorder state based on the power of
the first electroencephalogram measured at the first region and
that of the second electroencephalogram measured at the second
region.
[0073] In the above description, the frequency band (for example,
greater than or equal to 10.5 Hz and less than or equal to 12.5 Hz)
of the slow sleep spindles is set as the specific frequency band
for use in the diagnosis of the diagnosis part 114. However, the
specific frequency band is not limited to the frequency band of the
slow sleep spindles. Any specific frequency bands showing the same
tendency as that of the slow sleep spindles can be set as the
specific frequency band for use in the diagnosis. Hereinafter, a
description will be given of a case where the frequency band (for
example, greater than or equal to 12.5 Hz and less than or equal to
16 Hz) of the fast sleep spindles is set as the specific frequency
band.
[0074] FIGS. 9A and 9B are graphs showing the powers of the fast
sleep spindles measured at the respective regions of the head of
the test subject. FIG. 9A shows the powers of the fast sleep
spindles obtained when the test subject in the mood disorder state
is measured, while FIG. 9B shows the powers of the fast sleep
spindles obtained when the test subject in the normal state is
measured. The graphs shown in FIGS. 9A and 9B are obtained in such
a manner that the respective regions based on the International
10-20 system shown in FIG. 2 are measured. The comparison between
these graphs shows that the power of the fast sleep spindle at the
frontal region (the F region) is the greatest in the graph shown in
FIG. 9A, while the power of the fast sleep spindle at the top of
the head (the C region) is the greatest in the graph shown in FIG.
9B.
[0075] FIGS. 10A and 10B each display the distribution of the
powers of the fast sleep spindles measured at the respective
regions so as to be reflected in the shape of the head of the test
subject (the upper side of the head in each of FIGS. 10A and 10B
represents the front side of the test subject). FIG. 10A shows the
distribution of the powers of the fast sleep spindles measured when
the test subject is in the mood disorder state, while FIG. 10B
shows the distribution of the powers of the fast sleep spindles
measured when the test subject is in the normal state. In FIGS. 10A
and 10B, the greater the powers of the fast sleep spindles, the
darker the regions are colorized. It is found that, when the test
subject is in the mood disorder state, the regions of the greater
powers of the fast sleep spindles exist on the front side of the
head (near the prefrontal region) as shown in FIG. 10A. On the
other hand, it is found that, when the test subject is in the
normal state, the regions of the greater powers of the fast sleep
spindles exist on a further rear side of the head (near the frontal
region) as shown in FIG. 10B.
[0076] Accordingly, similar to the case where the frequency band of
the slow sleep spindles is set as the specific frequency band, it
is possible to diagnose whether the test subject is in the mood
disorder state or the normal state by setting the frequency band of
the fast sleep spindles as the specific frequency band.
Specifically, when the test subject is in the mood disorder state,
the power of the first electroencephalogram (FIG. 5A) becomes
greater in the frequency band (greater than or equal to 12.5 Hz and
less than or equal to 16 Hz) of the fast sleep spindles as shown in
FIGS. 5A and 5B. On the other hand, when the test subject is in the
normal state, the power of the second electroencephalogram (FIG.
6B) becomes greater in the same frequency band of the fast sleep
spindles as shown in FIGS. 6A and 6B. In other words, using the
frequency band of the fast sleep spindles, it is possible to
diagnose whether the test subject is in the mood disorder state or
the normal state by the comparison between the power of the first
electroencephalogram and that of the second
electroencephalogram.
[0077] Further, when the test subject is in the mood disorder
state, the comparison between the distribution of the powers of the
slow sleep spindles shown in FIG. 8A and that of the powers of the
fast sleep spindles shown in FIG. 10A shows that the existence of
the regions of the greater powers on the front side of the head can
be notably seen in the slow sleep spindles (FIG. 8A and FIG. 10A).
Accordingly, it seems to be possible to more clearly diagnose
whether the test subject is in the mood disorder state or the
normal state by setting the frequency band of the slow sleep
spindles as the specific frequency band for use in the
diagnosis.
[0078] Note that the difference in the distribution of the powers
of the sleep spindles between the mood disorder state and the
normal state is assumed to be caused by the malfunction of a
thalamofrontal circuit in the mood disorder state. It is suggested
that the thalamofrontal circuit related to the rostal reticular and
the mediodorsal nucleus of a thalamus interferes with the sleep
spindles of about 12 Hz.
[0079] As described above, based on the difference in the
distribution of the powers of the electroencephalograms in the
specific frequency band between the mood disorder state and the
normal state, it is possible to diagnose whether the test subject
is in the mood disorder state or the normal state. The first
measurement electrode 121 and the second measurement electrode 122
are arranged at the regions at which the difference in the
distribution of the powers can be detected. Specifically, the first
region at which the first measurement electrode is arranged and the
second region at which the second measurement electrode 122 is
arranged can be set such that the first region and the second
region are on the front and rear sides of the head H of the test
subject, respectively. More specifically, the first region can be
set as the prefrontal region (the Fp region based on the
International 10-20 system), while the second region can be set as
the frontal region (the F region based on the International 10-20
system).
[0080] As the specific frequency band for use in the diagnosis, the
frequency band (generally 10.5 Hz to 16 Hz) of the sleep spindles
can be set. Particularly, the frequency band (generally 10.5 Hz to
12.5 Hz) of the slow sleep spindles is effective because the
difference in the distribution of the powers can be notably seen.
Note that the specific frequency band is not limited to the
frequency band of the sleep spindles, and any frequency bands are
available so long as the difference in the distribution of the
powers between the mood disorder state and the normal state can be
seen in the frequency bands.
[0081] As described above, using the electroencephalogram analysis
apparatus 100 according to the embodiment, it is possible to
provide an objective barometer indicating whether the test subject
is in the mood disorder state or the normal state. Because it is
only necessary for the test subject to be in a sleep state and only
a small burden is placed on the test subject to perform the
diagnosis, the present disclosure is also applicable to home
monitoring.
[0082] The present disclosure is not limited to the above
respective embodiments but can be modified without departing from
the spirit of the present disclosure.
[0083] Note that the present disclosure may also employ the
following configurations.
[0084] (1) An electroencephalogram analysis apparatus,
including:
[0085] an electroencephalogram acquisition part configured to
acquire a first electroencephalogram measured at a first region on
a head of a test subject and a second electroencephalogram measured
at a second region positioned behind the first region on the head
of the test subject; and
[0086] a comparison part configured to compare a power of the first
electroencephalogram in a specific frequency band with a power of
the second encephalogram in the specific frequency band.
[0087] (2) The electroencephalogram analysis apparatus according to
(1), in which
[0088] the first region is a prefrontal region, and the second
region is a frontal region.
[0089] (3) The electroencephalogram analysis apparatus according to
(1) or (2), in which
[0090] the first region is an Fp region defined based on the
International 10-20 system, and the second region is an F region
defined based on the International 10-20 system.
[0091] (4) The electroencephalogram analysis apparatus according to
any one of (1) to (3), in which
[0092] the specific frequency band is a frequency band of sleep
spindles.
[0093] (5) The electroencephalogram analysis apparatus according to
any one of (1) to (4), in which
[0094] the specific frequency band is a frequency band of slow
sleep spindles.
[0095] (6) The electroencephalogram analysis apparatus according to
any one of (1) to (5), in which
[0096] the frequency band of the slow sleep spindles is greater
than or equal to 10.5 Hz and less than or equal to 12.5 Hz.
[0097] (7) The electroencephalogram analysis apparatus according to
any one of (1) to (6), further including
[0098] a stage discrimination part configured to discriminate a
sleep stage of the test subject, in which
[0099] the first electroencephalogram is an electroencephalogram of
any of sleep stages 2 to 4 measured at the first region, and
[0100] the second electroencephalogram is an electroencephalogram
of any of the sleep stages 2 to 4 measured at the second
region.
[0101] (8) The electroencephalogram analysis apparatus according to
any one of (1) to (7), in which
[0102] the comparison part transforms the first
electroencephalogram into a frequency component to generate a first
electroencephalogram spectrum, transforms the second
electroencephalogram into a frequency component to generate a
second electroencephalogram spectrum, and compares an integral
value of the first electroencephalogram spectrum in the specific
frequency band with an integral value of the second
electroencephalogram spectrum in the specific frequency band.
[0103] (9) The electroencephalogram analysis apparatus according to
any one of (1) to (8), further including:
[0104] a diagnosis part configured to diagnose whether the test
subject is in a mood disorder state based on a comparison result of
the comparison part.
[0105] (10) The electroencephalogram analysis apparatus according
to any one of (1) to (9), in which
[0106] the diagnosis part diagnoses that the test subject is in the
mood disorder state when the power of the first
electroencephalogram in the specific frequency band is greater than
the power of the second electroencephalogram in the specific
frequency band.
[0107] (11) An electroencephalogram analysis program that causes a
computer to function as:
[0108] an electroencephalogram acquisition part configured to
acquire a first electroencephalogram measured at a first region on
a head of a test subject and a second electroencephalogram measured
at a second region positioned behind the first region on the head
of the test subject; and
[0109] a comparison part configured to compare a power of the first
electroencephalogram in a specific frequency band with a power of
the second encephalogram in the specific frequency band.
[0110] (12) An electroencephalogram analysis method, including:
[0111] acquiring a first electroencephalogram measured at a first
region on a head of a test subject and a second
electroencephalogram measured at a second region positioned behind
the first region on the head of the test subject; and
[0112] comparing a power of the first electroencephalogram in a
specific frequency band with a power of the second encephalogram in
the specific frequency band.
[0113] It should be understood that various changes and
modifications to the presently preferred embodiments described
herein will be apparent to those skilled in the art. Such changes
and modifications can be made without departing from the spirit and
scope of the present subject matter and without diminishing its
intended advantages. It is therefore intended that such changes and
modifications be covered by the appended claims.
* * * * *