Method and apparatus for brain waveform examination

• US 4,092,981 A
• Filed: 07/15/1976
• Issued: 06/06/1978
• Est. Priority Date: 07/15/1976
• Status: Expired due to Term

• Current Assignee: Perpetual Eucharistic Adoration Incorporated A Religious Corporation of CA
• Original Assignee: John Paul Ertl
• Inventors: Ertl, John Paul
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/705,400
• Time in Patent Office: 691 Days
• Field of Search: 128/2.1 B, 128/2.1 R
• US Class Current: 600/544
• 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

Abstract

A neural efficiency rating is arrived at by amplifying and band-limiting an EEG waveform of a subject, discarding those parts of the waveform during which alpha rhythm is present, and measuring the average frequency of the remainder of the waveform. By comparing the phases and amplitudes of the waveforms produced by opposite sides of the subject'"'"'s brain, abnormalities of brain function may be detected, which together with the neural efficiency rating serves to evaluate brain function.

Claims

1. A method of determining the average frequency of a sample of a band-limited EEG waveform in the presence of an intermittent interfering unwanted alpha rhythm waveform of relatively greater amplitude than the components of the wanted waveform and of a defined frequency range within said band limits, comprising sensing a subject'"'"'s brain waveform, limiting said waveform to frequencies within said band limits, detecting in a sample of said waveform at least every alternate zero crossing point in the waveform, counting the events defined by adjacent alternate crossing points, identifying events having durations respectively within and outside a range corresponding to the duration of a cycle of a waveform within the defined frequency range of the unwanted waveform, determining the number and the sum of the durations of the events having durations outside said range during said sample, and calculating from said number and said sum the average frequency of these latter events.

2. A method according to claim 1, wherein said number and said sum are determined by determining the total number of events in the sample, deducting from this total the number of events having durations within said range, determining the duration of the sample and deducting the duration of those events having durations within said range from the duration of the sample, and the so reduced total of events is divided by the so reduced duration of the sample to calculate the average frequency of the EEG waveform.

3. A method according to claim 1, wherein the EEG waveform bandwidth is about 4-40 Hz and the unwanted waveforms have a frequency range of about 7-12 Hz.

4. A method of obtaining data relating to the brain function of a subject, comprising sensing, amplifying and band limiting the subject'"'"'s brain waveform, detecting the presence of alpha rhythm in said waveform, discarding those portions of the waveform in which said alpha rhythm is present, and determining the average frequency of the remainder of the band limited waveform.

5. A method of providing data relating to the brain function of a subject comprising sensing the subject'"'"'s brain waveform, amplifying and band limiting said waveform, sensing at least each alternate zero crossing of said waveform, sensing the number and duration of the time intervals between said alternate zero crossings, isolating those intervals whose combined duration corresponds to the cycle length of an alpha event, and ascertaining the mean duration of the remaining intervals whereby to determine the mean frequency of the band limited waveform when alpha events are not taking place.

6. A method according to claim 5, including sensing the subject'"'"'s brain waveform from both sides of the brain simultaneously, similarly amplifying and band limiting both waveforms, comparing the mean amplitudes of the two amplified and band limited waveforms, and indicating the magnitude of any difference between said mean amplitudes.

7. A method according to claim 5, including sensing the subject'"'"'s brain waveform from both sides of the brain simultaneously, similarly amplifying and band limiting both waveforms, comparing the relative phases of the two amplified and band limited waveforms, and indicating the magnitude of any phase difference between the waveforms.

8. Apparatus for determining the average frequency of non-alpha events in the brain waveform of a subject, comprising electrode means to sense a subject'"'"'s brain waveform, an EEG amplifier receiving and amplifying signals from said electrode assembly, band limiting means receiving the output of said amplifier and operative to exclude unwanted components of the waveform, zero crossing detector means receiving said band limited signal and operative to detect at least each alternate zero crossing of the waveform so as to divide it into a series of events, means receiving the output of the zero crossing detector means and operative to detect which of said events have a duration corresponding to the periodicity of alpha rhythm, and means controlled by said output receiving means to collect sufficient data relating to the events detected thereby to define the average frequency of the non-alpha events.

9. Apparatus according to claim 8, including timer means to set a defined period wherein the data collection means includes means counting the total number of events in the defined period, means counting the total number of alpha events within the defined period, and means registering the total duration of the alpha events within said defined period.

10. Apparatus according to claim 9, wherein the data collection means includes computation means receiving the counts accumulated by said counting means and said registering means at the end of said defined period, and computing the average frequency of the non-alpha events to provide an output according to the following formula

11. Apparatus according to claim 9, wherein display means are associated with said counting means and said registering means to display their respective counts at the end of said defined period.

12. Apparatus according to claim 8, comprising duplicated electrode means, amplifiers, filters and zero crossing detectors, whereby to process signals from both sides of a subject'"'"'s brain simultaneously, and further including a phase difference detector receiving the outputs of the two zero crossing detector means, and means to receive the output of the phase difference detector and display the phase differences detected thereby.

13. Apparatus according to claim 12, further including means to detect the difference in amplitude of the signals in the two channels, and means to receive the output of the amplitude difference detector and display the amplitude difference detected thereby.