The effect of contradiction between the visual and the vestibular information on the human postural control has been analyzed by means of the artificial alteration to the visual feedback information. To give the stereoscopic vision depending upon the motion of the test subject's head to his eyes, the three dimensional visor display system has been developed. This system can separate the visual information about the head motion into the rotational and the translational components and alter them independently of each other by changing the corresponding display gains. In the first experiment, the test subjects stood upright and carried out the tracking tasks by using their head rotation in different combinations of the display gain. The body sway increased more in amplitude in the case where the reversed component of the rotational head motion was displayed than in the case where the component was not displayed. This means that it is more important for the postural control system to maintain the consistent relationship between the visual and the vestibular information rather than to acquire the amount of the feedback information. In the second experiment, the increase in the display gain of the rotational component increased the body sway more in amplitude than that of the translational component. It can be guessed that this phenomenon is related to a psychological constancy that the display gain with respect to the rotational component of the head motion is primarily unchangeable.

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The purpose of this study is to estimate tidal volume from mluti-lead electrocardiograms without devices such as a nose clip or a face mask. The estimating method proposed in this study assumes that the direction of the vector loop (DVL) determined by the orthogonal leads represents the change in lung volume. DVL is defined as the diagonal direction of the rectangle which circumscribes the QRS vector loop. Another estimating method using the direction of the mean electrical axis (DMA) is compared with the method using DVL. The standard lead electrocardiograms and the change in lung volume are measured in our experiment. The change in lung volume is obtained by electrical integration of respiratory flow. During measurement subjects (aged 22 to 44 years, 15 males and 1 female) are instructed to change their tidal volume (ranging from 0.2 to 2.0l) voluntarily. Correlation coefficients between tidal volume and the changes in DVL and DMA are calculated to evaluate the two methods. The correlation coefficients obtained from DVL range from 0.61 to 0.96 (mean=0.86), while those obtained from DMA range from 0.22 to 0.90 (mean=0.60). In 11 subjects, the correlation coefficients obtained from DVL are significantly larger than those obtained from DMA. These results indicate that the change in DVL is closely correlated with tidal volume and reflects tidal volume more accurately, and that the estimating method proposed in this study can be used for respiratory monitoring.

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Membrane capacitance measurements are important in studying the mechanisms of exocytosis and endocytosis cycle in the exocrine gland cells. It is expected that the cell membrane capacitance would change during this cycle because of changes of the surface membrane area. A patch clamp system to measure small capacitance changes was studied. 1) A capacitance cancellation circuit was designed to compensate the stray capacitances of the headstage of the patch clamp amplifier and of the electrode. The frequency response of the amplifier had a notched characteristic because of this cancellation circuit and differential amplifier stage. The frequency response was improved by using an operational amplifier with large gain-bandwidth product, and by using specially designed low-pass and high-pass filters. 2) Small capacitance changes of a membrane model were measured with a combined system of a patch clamp amplifier and a two phase lock-in amplifier. It was desired that an access conductance was made large in so far as possible. That made the error of the measurement system less. 3) The measurement system was applied to two different secretory cells, for analysing the responses of exocytosis to intracellular GTP-γS stimulation. In the whole cell configuration of the rat peritoneal mast cells GTP-γS stimulation caused a large increase in membrane capacitance but a small increase in membrane conductance. In the dispersed single acinar cell of mouse pancreas, however, the membrane capacitance change could not be detected because of a large increase in membrane conductance comparing to a near level of access conductance. It is suggested that this capacitance measurement system is applicable to the exocrine gland cells like mouse pancreatic acinar cells only under special conditions where membrane conductance change is reduced or access conductance is very high.

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Contracting muscle fiber is accompanied with a rumbling noise due to lateral expansion of the muscle fiber. It is referred to as muscular sound (MS). The purpose of the present study is to assess muscular function of patients with cerebral palsy (CP) using MS. MS was derived from the belly surface of the biceps brachii muscle by a contact acceleration sensor with a piezo-electric element. Twelve CP patients and 12 normal persons performed an isometric elbow flexion from 10% to 60% of their maximum voluntary contraction (MVC). The recorded MS was processed by the FFT method to determine its power spectral distribution (PSD). After being smoothed with the B-spline function, the PSD was separated into two Gaussian distributions with the simplex method: a relatively lower frequency distribution (D₁) and relatively higher frequency distribution (D₂). The PSD in both subject groups deviated towards the high frequency range with increase in muscle contraction and demonstrated a trend to bimodal distribution at contractions beyond 30% MVC. The power in patients was, however, significantly smaller than that in normal subjects. The mean frequency and standard deviation of D₁ showed a similar change with contraction level in both subject groups. These parameters of D₂ increased linearly along with contraction level; however, the increments at contraction levels beyound 30% MVC were extremely lower in CP patients compared with those in normal subjects. These findings suggest that CP patients have a disuse atrophy of muscle and muscular dysfunction may appear selectively in fast twitch muscle fibers.

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To make clear the characteristics of cuff-pressure fluctuation ΔP_c, which is the base of oscillometric method, real phenomena occurring in human brachial artery under the cuff were examined using various non-invasive techniques. In the experiment the following factors were measured. Cuff-pressure P_c, local arterial volume change, blood velocity, finger arterial pressure, etc. From the experiments following results are obtained. ΔP_c wave-forms agree well with those of arterial volume change, but their amplitude ratio is a function of cuff-pressure whose changing rate is high in low cuff-pressure region. When wave reflection at near the cuff downstream margin does not occur, the shape of the artery under the cuff tapers off downstream and, hence, static model analysis is not good for this P_c region. The wave reflection is caused by recovery of arterial pressure distal to the cuff and increases arterial volume change of distal half and changes the ΔP_c profile. Hence the arterial pressure distal to the cuff is one of important factors to be considered.

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We have proposed an eddy current superposing tetrapolar circuit method to detect the impedance changes in a pair of closely-situated two parts of living tissue independently and simultaneously. In this paper, we applied this method to rheoencephalography (REG), and compared REG measured by this method and that by the conventional method. For simultaneous measurement by the both methods, we used constant currents of three frequency components. Two frequency components of these currents were used for the proposed method and the other one was for the conventional method. Measurements of REG were performed for cases with such as electric stimulation to the pollex or visual stimulation to the eyes. By the proposed method, impedance decreases corresponding to the activation of the brain were exclusively measured in the respective parts of the head, for example, in the contrateral hemisphere for the electric stimulation to the pollex. Such a localized impedance change was also obtained in the occipital part as a result of visual stimulation to the eyes. Fog repetitive experiment of touching stimulation to the face using soft paper, moreover, the impedance change suggesting a habituation process of the brain activity was observed. By the conventional method, however, such changes were not detected. We think, therefore, that the effectiveness of the tetrapolar circuit method using magnetic field for REG measurement was shown by in-vivo measurement.

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