Device and method for sensing electrical activity in tissue

• US 20070055169A1
• Filed: 08/08/2006
• Published: 03/08/2007
• Est. Priority Date: 09/02/2005
• Status: Active Grant

• Current Assignee: Nielsen Consumer LLC (Nielsen Holdings plc)
• Original Assignee: Nielsen Company (US) LLC (RR Donnelley & Sons Company)
• Inventors: Lee, Michael, Lee, Hans
• Granted Patent: US 9,351,658 B2
• Time in Patent Office: Days
• US Class Current: 600/544
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/0015 characterised by features of the telemetry system
• CPC Class Codes: A61B 5/165 Evaluating the state of mind, e.g. depression, anxiety
• CPC Class Codes: A61B 5/291 for electroencephalography [EEG]
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• 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 5/6814 Head
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence

Abstract

An exemplary embodiment providing one or more improvements includes apparatus and methods for sensing electrical activity in tissue of a person in a manner which is substantially limits or eliminates interference from noise in a surrounding environment.

Claims

1. A method for sensing electrical activity in tissue of a user in an environment which can cause electrical noise in electronics, comprising:

detecting the electrical activity from the tissue between a first point and a second point on skin of the user and generating a voltage signal in response thereto which contains a signal of interest and undesired signals;

amplifying the voltage signal to amplify the signal of interest and undesired signals without substantially amplifying the noise, the amplification resulting in an output signal.

2. A method as defined in claim 1 wherein amplifying the voltage signal involves using electronic components which use a local voltage reference, the method further comprising:

connecting the second point directly to the local voltage reference.

3. A method as defined in claim 1 wherein amplifying the voltage signal involves using electronic components which use a local voltage reference and source voltages, the method further comprising;

locating the electronic components in an area in close proximity to the second point so as to substantially couple the local voltage reference and source voltages to the second point.

4. A method as defined in claim 1 wherein amplifying the voltage signal involves using electronic components in an electronics module and detecting the electrical activity involves using conductors extending from the electronics module to electrodes at the first and second points, the method further comprising:

electrically isolating the electronics module by keeping the module free of wires, optical fibers or other extensions other than the conductors extending to the electrodes.

5. A method as defined in claim 1, further comprising;

filtering the output signal to attenuate the undesired signals and isolate the signal of interest from the undesired signals.

6. A method as defined in claim 5, further comprising:

communicating the signal of interest to a computing device.

7. A method as defined in claim 6 wherein the signal of interest is communicated over a wireless link to the computing device.

8. A method as defined in claim 6 wherein the computing device displays information relating to the signal of interest.

9. A method as defined in claim 6 wherein the computing device produces audio related to the signal of interest.

10. A method as defined in claim 5 wherein the signal of interest relates to electrical activity in brain tissue of the user.

11. A method as defined in claim 5 wherein the signal of interest relates to electrical activity in muscle tissue of the user.

12. A method as defined in claim 5 wherein the signal of interest relates to electrical activity in heart tissue of the user.

13. A method as defined in claim 5 wherein filtering the output signal attenuates undesired signals below 4 Hz and above 12 Hz.

14. A method as defined in claim 5 wherein the signals of interest are Alpha and Theta band brain waves.

15. A method as defined in claim 1 wherein the second point is on the ear of the user.

16. A method as defined in claim 1 wherein the second point is approximately 4 inches from the first point.

17. A method as defined in claim 1 wherein the second point is on the forehead of the user.

18. A method as defined in claim 1 wherein the second point is within 8 inches of the first point.

19. A method as defined in claim 1 wherein the undesired signals include noise signals caused by environmental noise.

20. A method for sensing electrical activity in tissue of a user in a noise environment subjected to electrical noise, comprising:

connecting a sensor electrode with skin of the user at a first point;

connecting a reference electrode with skin of the user at a second point which is in a spaced apart relationship to the first point to allow the sensor electrode to sense the electrical activity in the tissue at the first point relative to the second point; and

providing an amplifier which is configured to amplify the electrical activity while substantially reducing the influence from the noise environment.

21. A method as defined in claim 20 wherein connecting the reference electrode with the skin of the user causes a contact resistance between a surface of the reference electrode and the skin, the method further comprising:

configuring the amplifier to allow a surface of the reference electrode to directly contact the skin of the user at the second point without having to prepare the skin or use a material which decreases the contact resistance.

22. A method as defined in claim 21 wherein the amplifier is configured to allow the contact resistance to be as high as 500,000 ohms.

23. A method as defined in claim 20, further comprising:

positioning the amplifier in close proximity to the reference electrode such that the reference electrode and the amplifier are substantially in the same noise environment.

24. A method as defined in claim 20, further comprising:

positioning the amplifier in close proximity to the reference electrode such that the reference electrode and the amplifier are coupled capacitively.

25. A method as defined in claim 20, further comprising:

positioning the amplifier at the temple and the reference electrode at the ear of the user.

26. A method as defined in claim 25 wherein the amplifier and reference electrode are positioned at the right temple and ear of the user.

27. A method as defined in claim 20, further comprising:

isolating a signal of interest from the sensed electrical activity by filtering the amplified electrical activity.

28. A method as defined in claim 27 wherein the signal of interest relates to electrical activity in brain tissue of the user.

29. A method as defined in claim 27 wherein the signal of interest relates to electrical activity in muscle tissue of the user.

30. A method as defined in claim 27 wherein the signal of interest relates to electrical activity in heart tissue of the user.

31. A method as defined in claim 27 wherein filtering the amplified electrical activity attenuates undesired signals below 4 Hz and above 12 Hz.

32. A method as defined in claim 27 wherein the desired signals are Alpha and Theta band brain waves.

33. A method as defined in claim 20 wherein the electrical activity is communicated over a wireless link to a display device.

34. A method as defined in claim 20 wherein the amplifier produces an output signal in analog form, the method further comprising:

converting the output signal from analog to digital.

35. A method as defined in claim 34 wherein the output signal is converted at a rate that is a multiple of 60 Hz.

36. A method as defined in claim 34 wherein the digital output signal is tested for data that is inconsistent with EEG data, and the inconsistent data is removed from the digital output signal.

37. A method as defined in claim 34 wherein the digital output signal is transformed using a discrete Fourier Transform to determine an energy spectrum signal based on the energy spectrum of the digital output signal.

38. A method as defined in claim 37 wherein the energy spectrum signal is divided into groups of 60 samples and separates the energy spectrum into 1 Hz wide bins.

39. A method as defined in claim 37 wherein the energy spectrum signal is divided into groups of 30 samples and separates the energy spectrum into 2 Hz wide bins.

40. A method as defined in claim 37 wherein the energy spectrum signal is divided into groups of samples and separates the energy spectrum into bins which each represent energy in a certain range of frequencies, and energy in bins that have 4-8 Hz are summed to create a Theta band energy signal.

41. A method as defined in claim 40 wherein energy in bins that have 8-12 Hz are summed to create an Alpha band energy signal.

42. A method as defined in claim 41 wherein a signal of interest is created by determining a ratio of the Alpha and Theta band energy signals.

43. A method as defined in claim 42 wherein the ratio is (Theta signal−

Alpha signal)/(Theta signal+Alpha signal).

44. A method as defined in claim 20 wherein the amplifier produces an output signal in analog form, the method further comprising:

sampling the output signal for a certain number of samples in each 1/60^th of a second; and

summing the samples from each 1/60^th of a second to create a processed signal with no 60 Hz interference.

45. A sensor circuit for sensing electrical activity in tissue of a user and isolating and amplifying a signal of interest from the sensed electrical activity, the circuit comprising:

a sensor electrode for placing on skin of the user at a first point;

a reference electrode for placing at a second point which is a distance away from the first point to allow the sensor electrode to sense the electrical activity and to produce a voltage signal relative to the second point which includes the signal of interest in response; and

an electronic module comprising;

a power source with positive and negative source voltages and a source reference voltage which is electrically connected to the reference electrode;

an amplifier connected to receive power from the power source and to receive the voltage signal from the sensor electrode and the power source reference voltage, and wherein the amplifier produces an output signal which is proportional to the voltage signal relative to the power source reference voltage; and

a filter portion which receives the output signal from the amplifier and attenuates electrical activity unrelated to the signal of interest while passing the signal of interest.

46. A sensor circuit as defined in claim 45, further comprising:

a communication section for communicating the signal of interest to a computing device.

47. A sensor circuit as defined in claim 46 wherein the computing device displays information relating to the signal of interest.

48. A sensor circuit as defined in claim 46 wherein the communication section includes a wireless transmitter and a wireless receiver which is used to communicate the signal of interest to the computing device.

49. A sensor circuit as defined in claim 48 wherein the wireless transmitter and receiver use radio frequency waves.

50. A sensor circuit as defined in claim 48 wherein the wireless transmitter and receiver use infrared light.

51. A sensor circuit as defined in claim 45 wherein the sensor electrode includes a surface made from a non-reactive material.

52. A sensor circuit as defined in claim 51 wherein the non-reactive material is copper.

53. A sensor circuit as defined in claim 51 wherein the non-reactive material is gold.

54. A sensor circuit as defined in claim 51 wherein the non-reactive material is a conductive rubber.

55. A sensor circuit as defined in claim 51 wherein the non-reactive material is a conductive plastic.

56. A sensor circuit as defined in claim 45 wherein the distance between the first point and the second point is about 4 inches.

57. A sensor circuit as defined in claim 45 wherein the distance between the first point and the second point is less than 8 inches.

58. A sensor circuit as defined in claim 45 wherein the electrical activity is in brain tissue of the user.

59. A sensor circuit as defined in claim 45 wherein the electrical activity is in heart tissue of the user.

60. A sensor circuit as defined in claim 45 wherein the electrical activity is in muscle tissue of the user.

61. A sensor circuit as defined in claim 45 wherein the power source includes a charge pump.

62. A sensor circuit as defined in claim 45 wherein the signal of interest is from 4 to 12 Hz.

63. A sensor circuit as defined in claim 45 wherein the signal of interest is related to Alpha and Theta band brain waves and the filter attenuates 60 Hz and harmonics of 60 Hz signals.

64. A sensor circuit as defined in claim 45 wherein the first point is on the forehead of the user and the second point is on the right ear of the user.

65. A sensor circuit as defined in claim 45 wherein the sensor electrode is mounted to a frame which is supported by ears and nose bridge of the user.

66. A sensor circuit as defined in claim 65 wherein the electronic module is also supported by the frame.

67. A sensor circuit as defined in claim 45 wherein the sensor electrode is held against the skin of the user at the first point using an elastic band.

68. A sensor circuit as defined in claim 67 wherein the electronic module is supported by the elastic band.

69. A sensor circuit as defined in claim 67 wherein the elastic band extends around the head of the user to hold the sensor electrode against the skin of the forehead of the user at the first point.

70. A sensor circuit as defined in claim 67 wherein the elastic band forms a portion of a hat.

71. A sensor circuit as defined in claim 45 wherein the sensor electrode is held against the skin of the user with a mounting device that provides for 1.5 oz. of force to press the electrode against the skin.

72. A sensor circuit as defined in claim 45 wherein the sensor electrode is held against the skin of the user with a mounting device that provides for 1 to 4 oz. of force to press the electrode against the skin.

73. A sensor circuit as defined in claim 45 wherein the electronic module further comprises:

an averaging circuit for removing substantially all 60 Hz and harmonics of 60 Hz signals from the signal of interest.

74. A system for sensing electrical activity in tissue of a user, comprising:

means for detecting electrical activity from the tissue of the user at a first point on the skin of the user relative to a second point which is in a spaced apart relationship to the first point and generating a voltage signal in response thereto which contains a signal of interest and undesired signals;

means for amplifying the voltage signal to amplify the signal of interest and the undesired signals without substantially amplifying the noise, the amplification resulting in an output signal.

75. A system for sensing electrical activity in tissue of a user, comprising:

an arrangement which detects electrical activity from the tissue of the user at a first point on the skin of the user relative to a second point which is in a spaced apart relationship to the first point and generating a voltage signal in response thereto which contains a signal of interest and undesired signals;

an arrangement which amplifies the voltage signal to amplify the signal of interest and the undesired signals without substantially amplifying the noise, the amplification resulting in an output signal.