Surgery – Diagnostic testing – Detecting brain electric signal
Reexamination Certificate
1998-10-06
2001-01-16
Getzow, Scott M. (Department: 3737)
Surgery
Diagnostic testing
Detecting brain electric signal
Reexamination Certificate
active
06175762
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention concerns an EEG based activation system that may be used to turn an appliance or device ON or OFF. The system may also be used to provide proportional control, which could be used, for example, to vary the sound level output of a TV or stereo sound system.
2. Background Art
Considerable interest surrounds the detection, analysis and utilization of electrical signals generated within the brain. The detection and analysis of such signals by using electrodes pressed against the scalp to sense the signals is generally referred to as electroencephalography (EEG). The application of EEG to assist in medical diagnosis and in biofeedback studies is well established. Biofeedback using EEG, in which subjects may modify their EEG waveform in response to some visual stimulus, offers promise in control applications. Powerful signal processing tools such as artificial neural networks, are being incorporated to improve the reliability of similar systems.
Though significant advances in the utilization of EEG signals for control purposes through biofeedback methods have been made in recent years, a number of difficulties remain. In situations where the control of components in the EEG waveform must be learned, the training time using biofeedback methods may span from days to months. Not all subjects are capable of learning control through biofeedback and others are unable to transfer a learned effect out of a laboratory situation. Additionally, many low impedance contacts may need to be made to the scalp to sense EEG signals. This is time consuming, attracts user hostility, and over time ‘good’ electrical contact between one or more electrodes and the scalp may become impaired.
SUMMARY OF THE INVENTION
The present invention, as currently envisaged, provides an EEG based activation system. The system has an input port to receive electrical signals from scalp electrodes, an amplifier to amplify the signals, a bandpass filter to filter the signals and a signal averager to smooth out the signals. The speed and reliability of the system are provided by the signal averager which integrates any received signal in the passband of the filter and provides a ramping output. The integrating time constant may be between 1 and 5 seconds, and is advantageously around 2 seconds to give a tradeoff between spurious switching and switching delay.
The EEG based activation system is electronic technology which allows a person to rapidly and remotely control electronics devices or appliances in the environment using their brain signals. The system requires no training and the self controlled signal that is harnessed by the system is highly reliable and reproducible. It is not based on biofeedback principles and no training is required to operate the system.
The bandpass filter passes signals in the alpha-band, between 8 and 13 Hz, since human subjects consistently show an increase in alpha activity upon eye closure. The filter advantageously passes signals in the range 9 to 11 Hz since these signals show a consistent change in average level when the eyes are opened and closed.
A comparator may compare the smoothed signal with a reference and provide an output signal that changes state whenever the smoothed signal exceeds a predetermined threshold. The reference will generally be derived through trial and error. As the output voltage from the signal averager increases approximately linearly with time, the system can be adapted for multi-level switching or even proportional control.
A noise protection module may receive the signals from the electrodes and extract a noise band using another bandpass filter. This noiseband signal may also be averaged, and then be used to freeze the output of the activation system when the averaged noise signal exceeds a predetermined threshold. The noiseband may be between 27 to 29 Hz to pick up noise due to head movement and teeth grinding.
Embodiments of this system allow a person to activate an electrical appliance or device through self-control of EEG signals without the training that biofeedback requires. In a preferred form it involves a subject closing their eyes, opening their eyes or both opening and closing their eyes. Indications are that in excess of 90% of the adult population is able to effect this control.
The system may be made insensitive to sources of interfering signals such as eye movement, blinking or external electromagnetic interference.
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J.R. Wolpaw et al, “An EEG-Based Brain-Computer Interface for Cursor Control”, Electroencephalography and Clinical Neurophysiology, vol. 78, No. 3, Mar. 1, 1991, pp. 252-259.
Craig Ashley Ronald
Kirkup Leslie
McIsaac Paul Francis
Searle Andrew Peter
Christie Parker & Hale LLP
Getzow Scott M.
University of Technology Sydney
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