JPH0595925A - Light stimulator for visual evoked brain magnetic wave measuring apparatus - Google Patents

Abstract

PURPOSE:To enable the measurement of a fine visual evoked brain magnetic wave by flashing an arbitrary pattern with a leakage magnetic flux noise small sufficiently and with sufficient contrast and brightness at a high speed to be presented to a person to be inspected. CONSTITUTION:A plurality of light emitting elements are so arranged to form a specified light stimulation pattern so that an arbitrary pattern with a leakage magnetic flux noise small sufficiently and with sufficient contrast and brightness can be flashed at a high speed to be presented to a person 5 to be tested. An inversion pattern section 4 which comprises light emitting elements of the light stimulation pattern section 2 and a plurality of elements with the current consumed equal to that of the light emitting elements of the light stimulation pattern section 2 are arranged so that a pattern inverted for a light stimulation pattern of the light stimulation pattern section 2 is formed with respect to the light stimulation pattern section 2 which applies a light stimulation to the person 5 to be tested. Thus, the current consumed of a light stimulator as a whole in operation can always be maintained constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures the evoked magnetoencephalogram generated by photostimulation among the cerebral magnetoencephalograms, which are minute biological magnetic fields generated from the human brain, to measure physiological and basic medical functions of the brain. The present invention relates to an optical stimulator used in a magnetoencephalography device used for research and clarification, medical treatment and treatment of brain diseases, and the like.

[0002]

2. Description of the Related Art Conventionally used visual evoked brain magnetic wave measurement systems have used a TV display to post a pattern or have a colored glass or the like on which a pattern is drawn in front of a strobe light to blink the pattern. Has been adopted. However, unlike the EEG measured directly as the potential difference on the scalp, in the EEG measurement system, which is weak against noise, especially magnetic flux noise, the magnetic flux noise generated by the screen scanning and the blinking of the lamp is large in the TV display and the strobe light, and is practical Cannot be used.

To solve this problem, FIG. 4 of the accompanying drawings
As shown in, an image display device A such as a TV display or a liquid crystal display, which is a source of magnetic flux noise, is placed away from the brain magnetic wave detection coil B, and a decrease in the angle of view caused by it is magnified by a lens C, A visual evoked brain magnetic wave measurement system has been proposed which is configured to be projected on a transmissive slide screen D and displayed on a subject. However, with this method, it is impossible to post a pattern having a sufficient contrast necessary for a photostimulation device, the pattern illuminance is low, and the pattern switching time is long, so that the photostimulation device that can be put to practical use is provided. Has not yet been provided.

Therefore, as a photostimulation device having sufficient contrast and brightness necessary for a photostimulation device for visually evoked brain magnetic waves, a plurality of light emitting elements are arranged and a pattern is formed by blinking each light emitting device. It is considered that it is optimal to perform optical stimulation, and from this point of view, one conventional example of a conventional optical stimulation apparatus in which a pattern is configured by utilizing blinking of a light emitting element is shown in FIG. In FIG. 5, E is the main body of the optical stimulator, and is composed of several point-source-like light emitting diodes F.
And these light emitting diodes F are directly driven by the control device G. H is a magnetoencephalogram detection coil.

Further, in Japanese Patent Application No. 2-99366, a light stimulating device for performing light stimulation while switching a light emission pattern, and a signal processing device for processing a signal induced in response to light stimulation by the light stimulating device. A photostimulation-induced brain magnetic wave measurement device having a plurality of self-luminous light-emitting surfaces having light-emitting surfaces that are arranged closely to each other and form surface-emitting patterns that are mutually lit. The light stimulating device is configured to form an arbitrary light emitting pattern by switching the light emitting timing of each self light emitting device. Furthermore, Japanese Patent Application No. 2-2371
In No. 24, a brain magnetic wave measuring device used to measure the brain magnetic wave generated from the brain of the subject and perform physiological and basic medical research and elucidation of the function of the brain, medical treatment and treatment of brain diseases, etc. This method proposes a localization method and device, which externally stimulates a subject such as light or sound when resting, measures the evoked brain magnetic waves generated from the subject in response to this stimulus, and obtains the information thus obtained. , Which comprises calibrating the position based on the anatomical information of the subject to identify the position of the affected part of the subject in a magnetoencephalography device, and as an apparatus for performing this method, an optical stimulus signal to the subject. A stimulator, a device for measuring and processing brain magnetic waves induced in response to stimulation by an optical stimulator, and means for measuring anatomical information of the brain of a subject are provided.

In these earlier patent applications and the 5th Annual Meeting of the Biomedical Society of Japan (June 1-2, 1990), the effectiveness of pattern reversal stimulation consisting of a separate light emitting element in a visually evoked brain magnetic wave measuring device was shown. Was done. The pattern reversal stimulus is an optical stimulus in which square patterns are arranged in a checkerboard pattern and are alternately lit in a checkerboard pattern.The illuminance of the entire light emitting surface does not change over time, and only the pattern movement is applied to the subject. It is posted, and is suitable for diagnosing abnormalities of the visual nervous system and for verifying the visual information processing system of the subject with respect to a simple visual stimulus.

[0007]

By the way, it is known that the nervous system and the visual cortex that are excited are different depending on the pattern used for visual stimulation and the stimulation method.
In order to make a detailed diagnosis and to study the higher-order visual information processing mechanism possessed by humans, it is necessary to study using complex pattern stimuli such as figures and letters other than pattern reversal stimuli. However, unlike the pattern reversal stimulation generally used in the previously proposed methods, these complicated pattern stimulation methods cause a large change in the illuminance of the light emitting surface with time. Therefore, the method shown in FIG. Such a method of displaying a light pattern with a light emitting element is an ultra-sensitive magnetic sensor because the current value flowing in the photostimulation device changes greatly with time and the change in the magnetic flux leaking from the display device also increases accordingly. A biomagnetic measurement system using a superconducting quantum interference device (SQUID) has a problem that it is difficult to measure a minute visually evoked brain magnetic wave except when a simple point light source stimulus is used. For example, in a conventional photostimulation device using light emitting elements as shown in FIG. 5, each light emitting diode has a dozen mA when lighted.
When the number of light emitting diodes is increased in order to form a complicated pattern, the consumption current that fluctuates by blinking affects the brain wave detection coil, making it difficult to measure the visually evoked brain wave.

Therefore, the present invention solves the problems associated with the prior art and has sufficiently small leakage magnetic flux noise and sufficient contrast and brightness, which are necessary for ultrasensitive magnetoencephalography. An object of the present invention is to provide an optical stimulator for a visually evoked brain magnetic wave measuring device, which is capable of blinking an arbitrary pattern at high speed and displaying it on a subject so as to measure a minute visually evoked brain magnetic wave.

[0009]

In the present invention, of the magnetic flux noise leaking from the optical stimulator, the direct current component affects the visually evoked brain magnetic waves (generally in the frequency range of 1 to 1000 Hz). In view of this, therefore, in order to achieve the above-mentioned object, the optical stimulator for the visual evoked brain magnetic wave measuring device according to the present invention has a plurality of optical stimulators arranged to form a specific stimulation pattern. A light stimulus pattern section that is composed of a light emitting element and gives a light stimulus to a subject
Arranged to form an inverted pattern with respect to the photostimulation pattern of the photostimulation pattern part, and having each light emitting element of the photostimulation pattern part and an inversion pattern part composed of a plurality of elements having the same current consumption, It is characterized in that it is configured so that the total current consumption in the above is always kept constant. Each element of the inverted pattern portion may preferably be composed of the same light emitting element as each of the light emitting elements forming the photostimulation pattern portion, and the inverted pattern portion may be positioned in a position invisible to the subject. Alternatively, each element of the inversion pattern portion may be composed of a resistance element having the same current consumption as each light emitting element forming the photostimulation pattern portion.

[0010]

In the light stimulating device of the present invention having the above-described structure, the light stimulus pattern portion for giving the light stimulus to the subject, and the light stimulus pattern portion and the reversal pattern portion are biased in the mutually inverted state, that is, Depending on whether each light-emitting element of the planar light-emitting body in the stimulus pattern section is turned on or off, a plurality of elements in the reversal pattern section, each of which has a pattern inverted with respect to the light stimulus pattern and consumes the same current as the light-emitting element, are turned off. As a result, one of the light emitting element in the photostimulation pattern section and the element in the inversion pattern section is always energized at each position of the pattern, and the current consumption of the entire photostimulation apparatus is increased. Is almost constant, and the generation of leakage magnetic flux noise is suppressed.

[0011]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3 of the accompanying drawings. FIG. 1 schematically shows the configuration of a visual evoked brain magnetic wave measuring apparatus using an optical stimulating device according to an embodiment of the present invention. The illustrated optical stimulating device 1 includes an optical stimulating pattern unit 2, a light shielding plate 3, and an inversion pattern. Consists of part 4 and
The reversal pattern portion 4 is arranged on the rear side of the light shielding plate 3 so that the subject 5 cannot see it. Each of the light stimulus pattern portion 2 and the reversal pattern portion 4 has a rectangular outer shape of 15 mm × 15 mm and a light emitting surface of 14 mm × 14 mm. They are arranged in a matrix, that is, in a matrix. Each light emitting diode is connected to a light emitting diode drive circuit (not shown). In FIG. 1, 6 is a control device provided at a position sufficiently distant from the photostimulation device 1 so that the blinking of each light emitting diode of the photostimulation pattern unit 2 is always inverted with the light emitting diode of the corresponding position in the reversal pattern unit 4. In addition, the operation of the optical stimulator 1 is controlled. Therefore, the control device 6 has a logic circuit 7 as shown in FIG.
A pattern setting device 8 including a switch, a rectangular wave oscillating circuit 9 for setting the blinking time of the pattern, and a power supply 10 for each light emitting diode of the photostimulation device 1,
Each is connected as shown. Reference numeral 11 is a brain magnetic wave detection SQUID system, which includes a detection coil 12. 13 is a filter unit equipped with a low-frequency cutoff filter, a high-frequency cutoff filter, and a power line noise cutoff filter, and 14 is an arithmetic mean-display device.

The operation of the illustrated apparatus thus configured will be described. If the light emitting diode in the i-th row and the j-th column of the light stimulation pattern portion 2 is D _ij and the light emitting diode in the inversion pattern portion 4 at a position corresponding to this is D _ij ′, the light emitting diode D _ij and the light emitting diode D _ij are generated at a certain moment during operation. Since only one of the light emitting diodes D _ij ′ is turned on, the current consumption I ij of each part specified in the i-th row and the j-th column is substantially constant regardless of time, and therefore the current consumption of them is The sum of I _ij , that is, the current I _D (I _D = ΣijI _ij ) supplied from the power supply 10 to the photostimulation apparatus 1 becomes almost direct current, and the detection coil 12 of the SQUID system 11 for detecting a brain magnetic wave is shown.
Only produces a steady DC magnetic field. This DC component is easily removed by the low-frequency cutoff filter in the filter unit 13. Further, the filter unit 13 also deals with transient switching noise generated when the light emitting diodes in the light stimulation pattern section 2 and the inversion pattern section 4 blink.
Can be removed by a high pass filter at. The signal thus processed by the filter unit 13 is processed and displayed by the averaging-display device 14 with reference to the synchronizing signal from the rectangular wave oscillation circuit 9 in the control device 6.

FIG. 3 shows an example of the measurement of the visually evoked magnetoencephalographic wave measured with the illustrated apparatus. In this case, as the light stimulus, four central light emitting diodes in the light stimulus pattern portion 2 shown by hatching in FIG. 1 are simultaneously turned on for 500 msec and 500 msec.
The LEDs are turned off periodically, and the remaining 12 light emitting diodes in the surrounding area are always turned off.Blinking in a square pattern is used, and the brightness of each of the four light emitting diodes is 50 Cd / m ²
The measurement chamber was turned off and the measurement was performed. The distance between the eye of the subject 5 and the photostimulation pattern unit 2 of the photostimulation device 1 was set to 50 cm, and the left half side visual field stimulation was performed by the right eye monocular. A second-order differential gradiometer is used for the detection coil 12, and the origin 5 cm above the occipital process of the subject 5 is set along the scalp in a coordinate system with the horizontal direction as the X axis (+2 cm, +
The magnetic field appearing perpendicular to the scalp was measured at a point of 2 cm. The signal measured in this way is 0.3 in the filter unit 13.
The signal-to-noise ratio was improved by passing through a band pass filter of ˜100 Hz and a filter for blocking power line noise, and sending to an averaging-display unit 14 and averaging 200 times.

In the illustrated embodiment, the reversal pattern section 4 is composed of the same light emitting diode as the photostimulation pattern section 2, but the reversal pattern section 4 does not necessarily have to be composed of a light emitting diode. It is also possible to replace each light-emitting diode forming the pattern portion 2 with another element such as a resistor having the same current consumption, and in that case, the light shielding plate 3 can be omitted. In the circuit configuration of the device shown in FIG. 2, the logic circuit 7 in the control device 6 consumes an order of magnitude less than the current consumption of the photostimulation pattern unit 2 and the inversion pattern unit 4 in the photostimulation device 1. It can also be provided in the photostimulation device 1. Furthermore, in the illustrated photostimulation device, the number of light emitting diodes forming each of the photostimulation pattern unit 2 and the inversion pattern unit 4 is not limited to 16, and 16 or more light emitting diodes should be used. In that case, even if the number of light emitting diodes is increased, the consumption current does not change according to the blinking of the pattern, so that it is possible to form a complicated pattern such as a character. Furthermore, by changing the color, blinking time, etc. of the light-emitting diodes that make up the light stimulation pattern unit 2, it is possible to detect differences in visually evoked brain magnetic waves due to stimulation colors, complex color pattern stimulation, stimulation frequency dependence, etc. It can also be used for research.

[0015]

As described above, the photostimulation device according to the present invention is provided with the reversal pattern part that reverses the photostimulation pattern part so that the current consumption of the photostimulation device as a whole is always constant. Since it is configured as
The current value flowing in the optical stimulator does not change significantly with time, which allows the visually evoked brain wave measuring device to measure even a minute visually evoked brain wave without being substantially affected by changes in the magnetic field. Therefore, it is possible to provide an optical stimulator with extremely little leakage magnetic flux noise.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 is a schematic block diagram showing an example of a circuit configuration of the device shown in FIG.

FIG. 3 is a graph showing an example of measurement of visually evoked brain magnetic waves by blinking green square stimuli detected by the device shown in FIG. 1.

FIG. 4 is a schematic diagram showing an example of a conventional technique.

FIG. 5 is a schematic diagram showing another example of the prior art.

[Explanation of symbols]

 1: Photostimulation device 2: Photostimulation pattern part 3: Light-shielding plate 4: Inversion pattern part 5: Subject 6: Control device 7: Logic circuit 8: Pattern setting device 9: Rectangular wave oscillation circuit 10: Power supply 11: Brain magnetic wave detection SQUID system for use 12: Detection coil 13: Filter unit 14: Addition average-display device

Claims (4)

[Claims] 1. A photostimulation device used in a device for measuring a visually evoked electroencephalogram generated by photostimulation among magnetoencephalograms, which are minute biomagnetic fields generated from the brain of a subject,
It is composed of a plurality of light emitting elements arranged so as to form a specific light stimulus pattern, and forms a light stimulus pattern part that gives a light stimulus to a subject and a pattern that is the reverse of the light stimulus pattern of this light stimulus pattern part. Arranged, each light emitting element of the photostimulation pattern section and an inversion pattern section composed of a plurality of elements having the same current consumption, characterized in that it is configured to always maintain a constant overall current consumption during operation. Optical stimulator for visually evoked brain magnetic wave measuring device. 2. The device according to claim 1, wherein each element of the inversion pattern portion is composed of the same light emitting element as each light emitting element constituting the light stimulation pattern portion, and the inversion pattern portion is positioned in a position invisible to the subject. An optical stimulator for a visually evoked brain magnetic wave measuring device according to claim 1. 3. The optical stimulator for a visual evoked brain magnetic wave measuring apparatus according to claim 2, wherein the optical stimulus pattern portion and the inverted pattern portion are arranged in front and back through a light shielding plate. 4. The optical stimulator for a visually evoked brain magnetic wave measurement device according to claim 1, wherein each element of the inversion pattern portion is composed of a resistance element having the same current consumption as each light emitting element constituting the optical stimulation pattern portion.