Prevention of distortion of brainwave data due to eye movement or other artifacts

• US 4,171,696 A
• Filed: 01/30/1978
• Issued: 10/23/1979
• Est. Priority Date: 01/30/1978
• Status: Expired due to Term

• Current Assignee: New York Medical College (Touro College & University System)
• Original Assignee: John E. Roy
• Inventors: John, E. Roy
• Primary Examiner(s): Kamm, W. E.
• Application Number:
  US05/873,119
• Time in Patent Office: 631 Days
• Field of Search: 128/2.1 B, 128/2.1 M, 128/2.1 R, 128/2.06 B
• US Class Current: 600/544
• CPC Class Codes: A61B 5/276 Protection against electrode failure
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: A61B 5/398 Electrooculography [EOG], e.g. detecting nystagmus; Electroretinography [ERG]

Abstract

Eye and head movements produce large voltages which obscure the electrical activity of the brain, interfering with diagnostic procedures. In the system and method of the present invention electrical response to such movement artifact is detected by a set of electrodes and transmitted to amplifiers, analog-to-digital converters and an on-line to a digital computer. The computer monitors each of the 19 channels corresponding to the 19 electrodes on the subject'"'"'s head and a pair of electrodes located diagonally above and below one eye (trans-orbital) to detect artifacts associated with eye movement. Each channel of brain waves and artifact signals, converted into digital information, are compared with a threshold selected digital value set by the operator either by using standard values, by empirically eliciting sample artifacts, or by a standard deviation determination. The computer, after determining that there exists a movement artifact, i.e., an artifact in excess of the digital threshold value, either blanks out the brain wave data for that period or magnetically "marks" the appropriate channel(s) of the multi-channel recording at the time corresponding to the artifact distortion, which may be in all or only some channels.

Claims

1. A method in electroencephalography to decrease misleading effects from movement artifacts arising from the subject under test during the recording of the subject'"'"'s brain waves, including the steps of:

removably attaching a brain wave detection electrode to the scalp of the subject under test to detect the subject'"'"'s brain waves and produce an electrical signal corresponding to said brain waves;

removably attaching two muscle artifact electrodes across one of the subject'"'"'s eyes in a trans-orbital position to detect movement artifact and produce electrical signals corresponding to said detected movement artifact;

amplifying the said electrical signals from the brain wave electrode and converting the amplified brain wave signals into digital form;

amplifying the said movement artifact signals and converting the amplified signals into digital form;

establishing a threshold value in digital form of artifact activity by establishing a set of rest values for artifact and brain wave activity and automatically obtaining or arbitrarily defining a predetermined deviation therefrom;

modifying the amplified brain wave signals when said amplified movement artifact signals exceed said established threshold value; and

recording said modified brain wave signals.

2. The method of claim 1, wherein said modification is the use of those movement artifact signals in excess of the threshold to blank out the recording of the simultaneously occurring brain waves.

3. A method in electroencephalography to decrease misleading effects from movement artifacts arising from the subject under test during the recording of the subject'"'"'s brain waves, including the steps of:

removably attaching a brain wave detection electrode to the scalp of the subject under test to detect the subject'"'"'s brain waves and produce an electrical signal corresponding to said brain waves;

removably attaching two muscle artifact electrodes across one of the subject'"'"'s eyes in a trans-orbital position to detect movement artifact and produce electrical signals corresponding to said detected movement artifact;

amplifying the said electrical signals from the brain wave electrode and converting the amplified brain wave signals into digital form;

amplifying the said movement artifact signals and converting the amplified signals into digital form;

establishing a threshold value in digital form of artifact activity by establishing a set of rest values for artifact and brain wave activity and automatically obtaining or arbitrarily defining a predetermined deviation therefrom;

marking the amplified brain wave signals when said amplified movement artifact signals exceed said established threshold value; and

recording said marked brain wave signals.

4. An electroencephalographic system to decrease misleading effects from movement artifact of the subject under test during the recording of the subject'"'"'s brain waves, including:

a removably attachable brain wave detection electrode adapted to be attached to the scalp of the subject under test to detect the subject'"'"'s brain waves and produce an electrical signal corresponding to said brain waves;

two removably attachable movement artifact electrodes which are attached across one of the subject'"'"'s eyes in a transorbital position to detect movement and produce electrical signals corresponding to said movement;

an amplifier connected to said brain wave electrode to amplify the said electrical signals from the brain wave electrode;

a first analog-to-digital converter to convert said brain wave signals into digital form;

an amplifier connected to said movement artifact electrodes to amplify the said movement artifact signals;

a second analog-to-digital converter to convert said movement artifact signals into digital form;

means to determine base line values for said movement artifact and brain wave signals based upon the subjects at rest;

means to automatically fix a minimum threshold in digital form for said movement artifact signals based upon a selected statistical standard and said base line values;

means to modify the amplified brain wave signals based upon said amplified movement artifact signals in excess of said threshold; and

means to record said modified brain wave signals.

5. A system as in claim 4 and further including a digital computer connected to said analog-to-digital converters and a multi-channel recorder connected to said digital computer to record the same amplified brain wave and movement artifact signals in parallel tracks on the same record.