METHOD AND APPARATUS FOR AUTOMATIC ANALYSIS OF BRAIN WAVE SIGNALS

• US 3,760,796 A
• Filed: 09/29/1971
• Issued: 09/25/1973
• Est. Priority Date: 09/29/1971
• Status: Expired due to Term

• Current Assignee: Harvey F. Glassner, Lech Pisarski, Lee R. Baessler
• Original Assignee: Harvey F. Glassner, Lech Pisarski, Lee R. Baessler
• Inventors: Baessler, Lee R., Pisarski, Lech, Glassner, Harvey F.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/184,825
• Time in Patent Office: 727 Days
• Field of Search: 128/2.5T,2.6A,2.6F,2.1B,2.1R 328/136,140
• US Class Current: 600/544
• 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 5/7242 using integration

Abstract

A method and apparatus for the automatic analysis of the electroencephalogram waveform through the evaluation of the waves of the EEG waveform which occur within the frequency range from 3.5 Hz. to 7.0 Hz. within a predetermined time interval, e.g. 10 seconds. A linear ramp signal is generated for the time periods between zero crossovers of the EEG signal which represent a frequency within the 3.5 to 7 Hz. range. The cumulative amplitude that the ramp attains during the predetermined time interval is compared with a predetermined value to indicate a characteristic of the EEG waveform.

Claims

1. A method of evaluating EEG signals comprising the steps of:

a. detecting to be evaluated an EEG signal variable in both amplitude and frequency;

g. generating a first series of pulses related in occurrence to the frequency of the EEG signal;

c. generating a second series of constant amplitude pulses related in width to the temporal spacing of the pulses in the first series of pulses;

d. summing within a predetermined time interval the energy in the pulses in the second series of pulses by adding up to a predetermined maximum the energy in each pulse which exceeds a first predetermined width and by subtracting energy equal to the predetermined maximum for each pulse which exceeds a second predetermined width;

e. comparing the summed energy with a predetermined reference; and

, f. indicating the results of the comparison as an evaluation of the EEG signal.

2. The method of claim 1 including the steps of detecting the presence of 60 Hz. components above a predetermined value in the generated EEG signal;

and, inhibiting both the summing of energy and the running of the predetermined time interval responsively to the detection of the presence of 60 Hz. components above the predetermined value.

3. A method of EEG evaluation comprising the steps of:

a. detecting an EEG signal to be evaluated;

b. generating an output signal related in amplitude to the frequency of the EEG signal over a predetermined time interval;

c. comparing the amplitude of the output signal with a predetermined reference value; and

, d. indicating the results of the comparison as an evaluation of the EEG signal.

4. The method of claim 3 including the steps of inhibiting the generation of the output signal during the predetermined time interval in response to predetermined frequency components in the EEG signal.

5. The method of claim 4 including the step of extending the duration of the predetermined time interval by an amount equal to the time that the generation of the output signal is inhibited.

6. Apparatus for automatically evaluating an EEG waveform comprising:

means for providing an EEG waveform to be evaluated, said waveform being variable both in frequency and amplitude;

means for detecting the frequency of said EEG waveform;

means for generating a series of pulses having a width related to the detected frequency;

means for generating an output signal related to the integral oF the energy in the pulses in said series of pulses having a width within predetermined limits;

means for comparing said output signal with a predetermined reference; and

, means for indicating the results of the comparison as an evaluation of the EEG waveform.

7. The apparatus of claim 6 including means for detecting 60 Hz. signals in said EEG waveform to be evaluated;

and, means responsive to said 60 Hz. detecting means for inhibiting the evaluation of said EEG waveform.

8. The apparatus of claim 7 including timing means for limiting the duration of the operation of said output signal generating means, and means responsive to said evaluation inhibiting means for extending the duration of said output signal generating means.

9. Apparatus for automatically evaluating an EEG signal comprising:

electrode means for providing an electrical signal related to brain activity;

means for generating pulses related in energy content to the frequency of said electrical signal;

means for providing an ouput signal related to the integral of the energy in selected ones of said pulses; and

, means for comparing said energy related signal with a predetermined reference and for indicating the result of the comparison as an evaluation of the EEG signal.

10. The apparatus of claim 9 wherein the relationship between the energy content of said pulses and the frequency of the EEG signal is inverse.

11. The apparatus of claim 10 wherein said pulses are uniform in amplitude and variable in width.

12. The apparatus of claim 11 wherein said output signal generating means is functionally responsive only to pulses having a width within a predetermined range.

13. The apparatus of claim 12 wherein said pulse width range corresponds to a frequency range of about 3.5 Hz.

14. The apparatus of claim 12 wherein said pulse width frequency range corresponds to frequencies between about 3.5 Hz. and about 7.0 Hz.

15. The apparatus of claim 9 including means for detecting power supply frequency components in said electrical signal, and means responsive to said detecting means for inhibiting said output signal generating means.

16. The apparatus of claim 9 wherein said pulses are uniform in amplitude and variable in width.

17. The apparatus of claim 16 wherein the width of said selected pulses corresponds to frequencies between about 3.5 Hz. and 7.0 Hz.

18. The apparatus of claim 9 wherein said pulse generating means includes:

a time varying signal generator means;

a binary means;

a first threshold detector means responsive to the attainment of a first predetermined value by said time varying signal for setting said binary means to a first condition; and

, means responsive to said electrical signal for resetting said binary means to a second condition.

19. The apparatus of claim 18 wherein said output signal generating means includes a second threshold detector means responsive to the attainment of a second predetermined value by said time varying signal for resetting said binary means to a second condition and for reducing the value of said output signal by an amount equal to the energy in the pulse a width related to the time between the setting and resetting of said binary means.

20. The apparatus of claim 19 wherein the width of said selected pulses corresponds to a frequency between about 3.5 Hz. and 7.0 Hz.

21. A method of evaluating an EEG signal comprising the steps of:

a. providing a signal to be evaluated;

b. comparing the EEG signal to be evaluated with a predetermined reference to thereby define a series of time intervals;

c. providing a signal related to the cumulative duration of the time intervals within a predetermined range of time interval durations; and

, d. evaluating the cumulative duration of time interval related signals as an evaluation of the signal to be evaluated.

22. The method of claim 21 wherein the predetermined range of time intervals corresponds to a frequency range of about 3.5 Hz.