Patent No. 3893450 Method and apparatus for brain waveform examination

 

Patent No. 3893450  Method and apparatus for brain waveform examination (Ertl, Oct9, 1973)

Abstract

A method and apparatus for examining the brain waveform of a subject, for example in a type of electro-encephalography (EEG), by providing a stimuli, such as a light, and determining a characteristic of a mathematically determinable point in the brain waveforms of the subject. A number of brain waveforms are obtained after successive stimuli and where the mathematically determinable point is the zero crossing point, the time intervals to the second and third falling zero crossings in the brain waveform are considered to provide average values which are identified as the "A score" and the "B score" respectively and are utilized to indicate the condition of the subject. A closed loop feedback path may be used for stimulation of the subject.

 

Notes:

 

BACKGROUND AND NATURE OF THE INVENTION

This invention relates to a method and apparatus for determining the response of a subject to an external stimulus, for example, a video or sound stimulus. I have previously proposed the use of evoked potentials for determining the response of a subject in brain wave analysis or electro-encephalographs (EEG) -- see my U.S. Pat. No. 3,498,287 (issued Mar. 3, 1970) in which the information obtained was then used in assessing human intelligence.

During my work on the evoked responses of different subjects, I have established a statistically weak relationship between human intelligence as measured by IQ tests and various parameters of the electrical activity of the brain and I now believe that there are four general problems in attempting to use brain wave data to measure human intelligence:

A. The nature of human intelligence is poorly understood and its measure via IQ tests relies on a circular definition, i.e., that intelligence is a score on an IQ test.

B. Brain wave data sensed from the surface of the head are reflections of a large number of microscopic processes going on within the brain. Significant information concerning these processes is difficult to analyze and extract by conventional signal processing techniques.

C. Methods of sensory stimulation of the brain are critical in terms of understanding the underlying information processing activity within the matrix of brain cells.

D. There are a number of artefacts which impede the measurement of brain responses to stimulation. Some of these artefacts are of a physiological nature, whilst others are concerned with technological limitations of measurement and still others are due to electrical interference from the environment in which the subject is tested.

From one aspect, it is an object of the present invention to provide a method of determining the response of a subject to an external stimulus in which difficulties arising from the above-identified problems are substantially reduced or obviated.

Accordingly, the present invention provides a method of determining the response of a subject to an external stimulus including the steps of: positioning detection means in relation to a subject so as to detect the electrical activity of the brain of the subject; positioning a source of stimulation in an operative position in relation to the subject; providing control means for causing said source to be activated a number of times in succession to provide a plurality of subject stimuli; obtaining the resultant electrical activity by means of said detection means; generating a plurality of successive pulses, spaced from each other in time whereby each is capable of being effective to cause said source to be activated to produce an individual resultant brain waveform in said electrical activity; determining the passage of each of said resultant brain waveforms through at least one particular selected mathematically determinable point; determining a characteristic of said particular selected mathematically determinable point in the respective resultant brain waveform; and utilizing said brain waveform to provide an indication of the condition of the subject.

From another aspect of the present invention, it is an object to provide apparatus for determining the response of a subject to an external stimulus in which the inaccuracies of the above-identified problems are substantially reduced or obviated.

Accordingly, the present invention provides apparatus for determining the response of a subject to an external stimulus including detection means capable of being so positioned in relation to a subject as to be able to detect the electrical activity of the brain; a source of stimulation adapted to be positioned in an operative position in relation to the subject; control means for causing said source to be activated a number of times in succession to provide a plurality of patient stimuli; electrical connections to said detection means for obtaining the resultant electrical activity; pulse generating means capable of cooperating with said control means and for generating a plurality of successive pulses, spaced from each other in time whereby each is effective to cause said source to be activated to produce an individual resultant brain waveform in said electrical activity; first determining means for determining the passage of each of said resultant brain waveforms through at least one particular selected mathematically determinable point; characteristic determining means for determining a characteristic of said particular selected mathematically determinable point in the respective resultant brain waveform; and utilization means for utilizing said brain waveform to provide an indication of the condition of the subject.

The expression "mathematically determinable point, " as used in the present specification, will be understood to mean any point on a waveform which can be mathematically determined. The major points are, of course, the maximum point, the minimum point and the zero crossing points of the waveform. So far as EEG is concerned, mathematically determinable point may be regarded as any time-voltage co-ordinate either of the basic EEG or the amplitude average known as the evoked response following any method of sensory stimulation, such as photic, audatory, tactile, odorous or gustatory, -- any mathematical combination of the above-defined mathematical points may be used to improve the prediction of intelligence and/or IQ from brain-wave analysis. For example, step-wise multiple regression analysis.