ELECTRODE ATTACHMENT STATE DETERMINATION SYSTEM, ELECTRODE ATTACHMENT STATE DETERMINATION METHOD, AND PROGRAM THEREOF

• US 20120029336A1
• Filed: 09/02/2011
• Published: 02/02/2012
• Est. Priority Date: 12/15/2009
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: MORIKAWA, Koji, TERADA, Yoshihisa
• Granted Patent: US 10,226,198 B2
• Time in Patent Office: Days
• US Class Current: 600/383
• CPC Class Codes: A61B 2560/0276 Determining malfunction
• CPC Class Codes: A61B 2562/0215 Silver or silver chloride containing
• CPC Class Codes: A61B 5/291 for electroencephalography [EEG]
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/374 Detecting the frequency distribution of signals, e.g. detecting delta, theta, alpha, beta or gamma waves
• CPC Class Codes: A61B 5/6803 Head-worn items, e.g. helmets, masks, headphones or goggles
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure

Abstract

An electrode attachment state determination system includes: an electroencephalogram measurement section for measuring an electroencephalogram signal of a user by using at least one set of electrodes including a ground electrode, a reference electrode, and a measurement electrode; a frequency analysis section for performing a frequency analysis of the electroencephalogram signal; an insufficient electrode determination section for extracting at least one parameter of a total frequency power and a noise amount from a result of the frequency analysis, and through a comparison of a value of the parameter against a predetermined threshold value, determining whether the ground electrode, the reference electrode, or the measurement electrode has an insufficient state of attachment; and an output section for, when an insufficient state of attachment is determined, presenting information indicating the insufficient state of electrode attachment to the user.

Claims

1. An electrode attachment state determination system comprising:

an electroencephalogram measurement section for measuring an electroencephalogram signal of a user by using at least one set of electrodes, the set including a ground electrode, a reference electrode, and a measurement electrode;

a frequency analysis section for performing a frequency analysis of the electroencephalogram signal;

an insufficient electrode determination section for extracting at least one parameter of a total frequency power and a noise amount from a result of the frequency analysis, and through a comparison of a value of the at least one parameter against a predetermined threshold value, determining whether the ground electrode, the reference electrode, or the measurement electrode has an insufficient state of attachment; and

an output section for, when an insufficient state of attachment is determined, presenting information indicating the insufficient state of attachment of the electrode to the user.

2. The electrode attachment state determination system of claim 1, wherein the insufficient electrode determination section extracts the noise amount parameter from the result of the frequency analysis, and if the noise amount parameter has a value exceeding a predetermined first threshold value, determines that the ground electrode has an insufficient state of attachment.

3. The electrode attachment state determination system of claim 2, wherein the insufficient electrode determination section further extracts the total frequency power parameter from the result of the frequency analysis, and if the total frequency power parameter has a value exceeding a predetermined second threshold value, determines that one of the reference electrode and the measurement electrode has an insufficient state of attachment.

4. The electrode attachment state determination system of claim 3, wherein,

the electroencephalogram measurement section uses a plurality of sets of electrodes each including a ground electrode, a reference electrode, and a measurement electrode, to measure an electroencephalogram signal with each set;

the frequency analysis section performs a frequency analysis of each electroencephalogram signal; and

the insufficient electrode determination section

extracts a noise amount parameter from a result of the frequency analysis of each electroencephalogram signal, and if all of the extracted noise amount parameters have values exceeding a predetermined first threshold value, determines that the ground electrode has an insufficient state of attachment, and

extracts a total frequency power parameter from the result of the frequency analysis of each electroencephalogram signal, and if all of the extracted total frequency power parameters have values exceeding a predetermined second threshold value, determines that the reference electrode has an insufficient state of attachment, or if some of the extracted total frequency power parameters have values exceeding the second threshold value, determines that the measurement electrode has an insufficient state of attachment.

5. The electrode attachment state determination system of claim 1, wherein the electroencephalogram measurement section measures a first potential difference between the ground electrode and the reference electrode and a second potential difference between the ground electrode and the measurement electrode, and measures the electroencephalogram signal based on a difference between the second potential difference and the first potential difference.

6. The electrode attachment state determination system of claim 5, wherein,

a noise being steadily mixed from an external environment at a previously identified frequency is superposed on the electroencephalogram signal;

and

from the result of the frequency analysis, the insufficient electrode determination section extracts a frequency power of the noise as the noise amount parameter.

7. The electrode attachment state determination system of claim 6, wherein the previously identified frequency is a frequency of a commercial-power noise of a device which is in the external environment.

8. The electrode attachment state determination system of claim 5, wherein, as the total frequency power parameter, the insufficient electrode determination section extracts an average value of a power of the electroencephalogram signal in an analyzable frequency band.

9. The electrode attachment state determination system of claim 5, further comprising an electrode restoration determination section for determining, based on a signal measured by using an insufficient electrode which is determined as having an insufficient state of attachment, whether the insufficiency in the state of attachment of the insufficient electrode has been eliminated or not, wherein,

when the insufficient electrode is the ground electrode,

the electrode restoration determination section extracts the noise amount parameter from the result of the frequency analysis of the signal as measured by using the insufficient electrode, and, if the noise amount parameter has a value exceeding a predetermined third threshold value, the electrode restoration determination section determines that the insufficiency in the state of attachment of the insufficient electrode has not been eliminated, or if the noise amount parameter does not have a value exceeding a predetermined third threshold value, the electrode restoration determination section determines that the insufficiency in the state of attachment of the insufficient electrode has been eliminated.

10. The electrode attachment state determination system of claim 5, further comprising an electrode restoration determination section for determining, based on a signal measured by using an insufficient electrode which is determined as having an insufficient state of attachment, whether the insufficiency in the state of attachment of the insufficient electrode has been eliminated or not, wherein,

when the insufficient electrode is one of the reference electrode and the measurement electrode,

the electrode restoration determination section calculates an average value and variance of the signal as measured by using the insufficient electrode, and, if both of the average value and the variance are zero, the electrode restoration determination section determines that the insufficiency in the state of attachment of the insufficient electrode has not been eliminated, or if not both of the average value and the variance are zero, the electrode restoration determination section determines that the insufficiency in the state of attachment of the insufficient electrode has been eliminated.

11. The electrode attachment state determination system of claim 5, further comprising a measurement electrode replacement section for, based on prestored electrode information, replacing an insufficient electrode which is determined as having an insufficient state of attachment with a replacing electrode, wherein,

the electrode information describes information of a type and position of each of electrodes which are available for measuring an electroencephalogram signal of the user;

with respect to an insufficient electrode which is determined as having an insufficient state of attachment, the measurement electrode replacement section identifies the type and position of the insufficient electrode, and refers to the electrode information to identify the replacing electrode based on electroencephalographic characteristics of an electroencephalogram signal to be measured by the insufficient electrode; and

instead of the insufficient electrode, the electroencephalogram measurement section uses the identified replacing electrode to measure an electroencephalogram signal.

12. The electrode attachment state determination system of claim 11, further comprising an electroencephalogram processing section for distinguishing an intent of the user by utilizing a characteristic component contained in the measured electroencephalogram signal, wherein,

when the insufficient electrode is the measurement electrode, the measurement electrode replacement section refers to the electrode information to identify, as the replacing electrode, an electrode which is within a predetermined distance from the insufficient electrode and which is at a closest distance from a brain position where the characteristic component of the electroencephalogram signal is generated.

13. The electrode attachment state determination system of claim 11, further comprising an electroencephalogram processing section for distinguishing an intent of the user by utilizing a characteristic component contained in the measured electroencephalogram signal, wherein,

when the insufficient electrode is the reference electrode, the measurement electrode replacement section refers to the electrode information to identify, as the replacing electrode, an electrode which is within a predetermined distance from a mastoid.

14. The electrode attachment state determination system of claim 1, further comprising an electroencephalogram processing section for distinguishing an intent of the user by utilizing a characteristic component contained in the measured electroencephalogram signal, and executing a process which is in accordance with the intent of the user, wherein,

from a result of the frequency analysis, the insufficient electrode determination section extracts at least one parameter of a total frequency power and a noise amount, and through a comparison of a value of the at least one parameter against a predetermined threshold value, determines a state of attachment of the ground electrode, the reference electrode, or the measurement electrode to be sufficient or insufficient;

and

if the state of attachment is determined to be insufficient, the output section presents information indicating the insufficient state of attachment of the electrode to the user, and if the state of attachment is determined to be sufficient, the output section outputs a result of the process which is in accordance with the intent of the user.

15. An electrode attachment state determination method comprising the steps of:

measuring an electroencephalogram signal of a user by using at least one set of electrodes including a ground electrode, a reference electrode, and a measurement electrode;

performing a frequency analysis of the electroencephalogram signal;

from a result of the frequency analysis, extracting at least one parameter of a total frequency power and a noise amount, and through a comparison of a value of the at least one parameter against a predetermined threshold value, determining whether the ground electrode, the reference electrode, or the measurement electrode has an insufficient state of attachment; and

when an insufficient state of attachment is determined, presenting information indicating the insufficient state of attachment of the electrode to the user.

16. A computer program, stored on a non-transitory computer-readable storage medium, to be executed by a computer for determining a state of electrode attachment, wherein the computer program causes the computer to execute the steps of:

measuring an electroencephalogram signal of a user by using at least one set of electrodes including a ground electrode, a reference electrode, and a measurement electrode;

performing a frequency analysis of the electroencephalogram signal;

from a result of the frequency analysis, extracting at least one parameter of a total frequency power and a noise amount, and through a comparison of a value of the at least one parameter against a predetermined threshold value, determining whether the ground electrode, the reference electrode, or the measurement electrode has an insufficient state of attachment; and

when an insufficient state of attachment is determined, presenting information indicating the insufficient state of attachment of the electrode to the user.