Skin Potential Level (SPL) on the palmar surface increases at the early stage of sleep and recovers with arousal. We applied the phenomenon to sleep control by using the biofeedback technique. Two ways of control are possible : inhibition and promotion of sleep.
First, an SPL biofeedback system for doze suppression was constructed. In the system an alarm sound was issued to a subject when his SPL exceeded a certain threshold level. This doze alarm system was proved to operate well through a series of experiments.
Second, a possibility for promotion of sleep was tested by feeding back the SPL of a subject to himself with auditory information. The surf sound was adopted as the feedback signal. Our SPL biofeedback system was effective for subjects who suffered from sleeplessness as well as for normal people.
Such techniques will be applicable to a doze alarm system for drivers, to clinical therapy of sleep disorder, and so forth.

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In clinical EEG recording by monopolar derivation, earlobe is usually used as a reference point. But this point is more or less influenced by temporal activity. While the balanced non-cephalic reference electrode method (B reference electrode method) is theoretically ideal for monopolar derivation, this method has some drawbacks, e. g., the ECG artifacts.
In this paper, we present the principle and the device for eliminating the ECG artifacts, when using the B reference electrode method. EEG signals with ECG artifacts (original EEG signals) derived from the B reference electrode method were averaged by computer which was triggered by QRS complex, and, consequently, averaged ECG pattern mixed in EEG signal was detected. Then the averaged ECG pattern was subtracted from the original EEG signals. By these procedures ECG artifacts were eliminated without deformation of EEG signals. Amplitude difference between averaged ECG and individual ECG mixed in EEG was indicated by percentage for averaged ECG amplitude which was 10-15%. If the amplitude of ECG artifacts derived by the B reference electrode method was 100 μV, this percentage (10-15%) was negligible because this value was equivalent to deflection of 10-15 μV in the EEG record. It was confirmed that our method of ECG elimination was also available for subjects with arrthymias, but not for some subjects with transiently deformed ECG pattern, e. g., ventricular premature beat.
EEGs recorded by the B reference electrode method using our device were compared with those recorded by the traditional monopolar method with the reference electrode at the earlobe. The difference was also shown as the power spectra. It was concluded that the B reference electrode method with our device was more available than the traditional reference electrode method, especially for measurement of amplitude, phase-relation and distribution of EEG activity.

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Response characteristics of human operators in manual pursuit tracking with auditory input are investigated. The human operator hears through his left ear a sound whose frequency varies in proportion to an external random signal. At the same time, he hears through his right ear another sound whose frequency varies in proportion to the angle of the control lever of a potentiometer. The operator controls the angle of the lever so that the frequencies of the sounds in both ears remain as close as possible. The dynamics of the human operator is studied by assuming a 'man-machine system' whose input is the external signal and whose output is the voltage of the potentiometer. A learning identification method proposed by one of the authors is used to calculate the weighting function of the man-machine system, which is displayed on a CRT screen in real time.
Results of the experiments are summarized as follows;
(1) The shapes of the weighting functions of the auditory tracking systems are classified into two modes-the stable mode corresponding to smooth control, and the unstable one corresponding to awkward control.
(2) Smooth tracking controls are further divided into fine tracking and rough tracking.
(3) There are significant differences in tracking performance between subjects.
Comparisons of the results obtained from the auditory tracking system with those of visual and combined tracking systems show that (1) the visual tracking system is more stable than the auditory system only for relatively poor trackers, and (2) the response of the combined tracking system is most stable and rapid for all subjects.

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This paper describes a new and simpler method for measuring temporal MTF (Modulation Transfer Function) of human vision. The test pattern using a television monitor consists of temporal frequency bursts which are made of vertical stripes and are aligned from 1 Hz to 30 Hz in the horizontal direction. Contrast of the test pattern changes exponentially in the vertical direction. A subject traces the position at a threshold level of the test pattern under the natural viewing condition, and the temporal MTF of the subject is obtained within two minutes. The experimental value obtained with the proposed method agrees well with the result of the conventional single frequency method. This method is expected to find application in the eye clinics.

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For indirect measurement of both beat-to-beat systolic and diastolic pressures and pressure waveform in the human finger, a new hydraulic servocontrol system, which is to maintain the vascular volume in the unloaded state, has been designed. The proposed system consists of a compression chamber equipped with an occluding cuff and a transmittance photoelectric plethysmograph, an electromagnetic shaker, and a volume servo circuit. The shaker connected to a diaphragm actuator is used for controlling the chamber pressure (cuff pressure). The vascular volume change in the finger is detected by the photoelectric plethysmograph. The output signal from the plethysmograph is fed into the servo circuit to control the cuff pressure, which is clamped at a proper value corresponding to the unloaded vascular volume. At this state the cuff pressure thus automatically controlled follows the intra-arterial pressure. The accuracy of this method has been evaluated by both the in vitro experiment using a vascular model and the animal experiment using the rat's tail. Very close agreement between the simultaneous data from this method and the direct measurement was obtained. Comparisons with direct measurement w ere also carried out successfully in four normotensive and six hypertensive subjects.

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This paper describes several discussions about detection impedance of the endocardial electrodes related to the surface areas in order to evaluate the sensing function of cardiac pacemakers.
The conclusions reached are as follows :
(1) Detection impedance of the electrodes-meaning the electrode impedance when the electrodes are used to pick up the signals induced-were found to be approximately in inverse proportion to their surface areas. Polarization impedance became predominant under increasing detection impedance as the surface area became smaller. Therefore, reduction of electrode polarization is most effective to decrease the detection impedance, which would pose serious sensing problems for the pacemakers if conducted with such small electrodes.
(2) Detection impedance of the electrodes went down day by day during a few days after electrode implantation; it then increased gradually until the electrodes reached their own stable states.
This seems to be a safe side variation for pacemaker sensing because the decrease of detection impedance may compensate for the reduction of QRS amplitude that transitorily appears immediately after electrode implantation.

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From a law of physics, it is obvious that the momentum of blood ejected from heart during systole can be divided into two forms. The one is the momentum of blood running away distally and the other is that of the aortic root and blood in it. The motion of aortic root is related to the stroke volume by the equation of SV∝ D²V_ao^1/2× AOT, where D is the diameter of the aortic root, V_ao is the mean velocity of the anterior wall during systole and AOT is the duration of aortic valve opening. Stroke volume estimated by the present method was found to be highly correlated with the stroke volume measured by the thermodilution method (r=0.81, p<0.001). A similar correlation was also observed with stroke volume determined from the left ventricular dimensions in an ordinary manner. Since the parameters that appeared in the present method were not directly affected by the mode of heart contraction, such as symmetrical or asymmetrical, it may be useful to determine stroke volume even in a heart contracting asymmetrically.

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