We have examined the effect of single visual stimulus upon the amplitude and phase of alpha waves by a complex demodulation method. The frequency for demodulation is set with the peak frequency of the subjects' alpha activity. The visual stimuli were generated by LED-mounted goggls in an eyes-closed condition. The data for the analysis are measured at Pz, which is a dominant electrode for event-related potentials. The interstimulus interval (ISI) was 10sec with a constant interval. The subjects were 10 healthy adult students with normal vision. The amplitude of alpha wave decreased gradually after the stimulus, showing a minimum at around 300msec after stimulus. Then it recovered to the same level around 700msec after stimulus with the pre-stimulus amplitude level. It continued to increase showing some rebound, and returned again around 2, 200msec after stimulus. The averaged phase variation is calculated with the reference at stimulus onset as zero. The variation after stimulus tends to be significantly larger than that before stimulus. Averaged phase showed a uniform delay before stimulus and showed acceleration after stimulus. This means that the frequency after stimulus is higher than that before stimulus. Moreover, averaged phase returned to the same slope as pre-stimulus around 2, 550msec after stimulus. According to the results of amplitude and phase variation, visual stimulus effects alpha waves until about 2, 500msec after the stimulus. Phase variation before and after stimulus shows significance from 112 to 678msec after stimulus. This result indicates that there are some relations between event-related potentials and alpha waves.

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Detection and extraction of a single waveform, which appears in electroencephalogram (EEG) data, are an important step for neurophysiological diagnosis. The correlation coefficient is a useful index for correlating two similar signals of variable amplitude, but does not apply to signals of variable duration. In this study, a similarity coefficient was defined and used for extracting the single waveform of both variable duration and variable amplitude. The similarity coefficient was defined by introducing a time-scale factor into the correlation coefficient to measure the similarity of two signals. A single waveform of variable duration and variable amplitude in an EEG record was accurately detected and extracted by the use of the similarity coefficient. The method was evaluated using the simulated data of a single waveform with noise and then applied to actual EEG data contaminated with epileptic spikes. The spikes were accurately detected and extracted from the raw EEG data using the similarity coefficient. Furthermore, the spikes were subtracted from the raw EEG to make the background EEG stand out. The proposed method, with the similarity coefficient, is widely applicable for extracting any kind of burst signal of EEG record and evoked potentials for extracting the characteristics of single waveforms.

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Using discrete wavelet transformation, we devised an improved method for focus detection in an automatic measurement system for counting numerical chromosomal aberrations per nucleus. In the previous system we had developed, the focus was determined by detecting the maximum intensity. However, the focus sometimes needed to be adjusted if it happened to be on the fluorescence noise that accompanied the preparation of specimens when the noise intensity was high. By using an appropriate level of wavelet transformation of the microscopic images, the focus position for cell nuclei could be obtained even in the presence of fluorescence. In addition, in the previous system, even if undamaged nuclei were selected correctly, the system picked up only a small proportion of nuclei that satisfied the criterion, which resulted in most nuclei being excluded from measurement. This also entailed the possibility of taking up an eccentric population of nuclei, and thus reducing the reliability of the measurement results. Therefore, we have attempted to find a criterion that will allow us to select a large proportion of undamaged nuclei. Since the contour of a good nucleus is close to a circle, circles having the minimum average difference from the contour of the nucleus, the smallest standard deviation, or the largest difference were chosen. Using these parameter values, the nuclei of lymphocytes suitable for measurement were determined, and 80% of the total nuclei among those considered suitable were correctly selected. By this method, the precision and reliability of the automatic counting system were improved.

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A radio frequency (RF) telemetry system with a shape memory alloy (SMA) microelectrode was designed and fabricated. The total size and weight are 15×8mm and 0.1g without batteries. Since the telemeter is small and light enough to be loaded on a small animal such as an insect with no restraint on motion, the system can work for the neural recording of a free-moving insect. The SMA microelectrode fabricated by microelectromechanical system (MEMS) technologies can easily attach to the nerve by electrically actuating the electrode structure. Also, it does not detach from the nerve during motion due to its clipping structures. The telemeter can transmit signals by frequency modulation (FM) transmission at 80-90MHz. The transmitted signals can be received about 16m away from the telemeter with a high S/N ratio. The neural activity can be detected without attenuation using an instrumentation a mplifier with input impedance set to 2MΩ at 1kHz. The telemeter was loaded on a cockroach and the neural activity during free-walking was successfully measured through this telemetry system.

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Transthoracic impedance or admittance cardiography has been one of the simple and useful methods for noninvasive monitoring of cardiovascular function. Generally, a tetra-polar band-electrode system proposed by Kubicek et al. has been used in this method. However, the band-electrode attachment is troublesome, makes the subject uncomfortable during long-term monitoring and is often inconvenient for clinical practice. We designed a new spot-electrode array in place of the band-electrode array. Its location was determined by measuring current distribution on the thorax using a 64-ch impedance mapping system. A uniform distribution of current density suitable for an electrical cylinder model of the thorax was evaluated using this mapping. The new spot-electrode array was developed and investigated for suitability in a cylindrical model using 11 normal male subjects in supine position. The current distribution made by the new spot-electrode array was similar to the uniform current distribution (γ=0.920-0.962, p<0.001) and capable of emulating the band-electrode array (γ=0.969-0.975, p<0.001). In a comparison between the new spot-electrode array and band-electrode array for impedance cardiography, the stroke volume values obtained by the spot electrode were 5-19% larger than those by the band electrode. The loss of uniform current distribution on the thorax under the impedance change related to cardiac ejection, which was observed in this study, may cause an over-estimation of the stroke volume measured by the new spot-electrode array.

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We realized a new electrical impedance tomography (EIT) based on the tetrapolar circuit method with the scanning of magnetic field superimposed for localizing the current distribution in biological tissues. In this method, two voltage differences are detected on two sides of the body, in which the distribution of constant current component is parallel. As the voltage difference of one side becomes zero, the eddy current component is produced by a magnetic field applied to the body from an electromagnetic core. Sustaining this state, the electromagnetic core is moved from side to side. The voltage differences at the other side measured during this movement of the magnetic field are used to estimate the resistance distribution of one dimension. As the result of a model experiment, it was confirmed that this method would be useful to realize EIT.

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A phenomenon called “Deh-chi” is described as a kind of soreness, numbness or heavy swelling in deep tissues during acupuncture. Deh-chi and the right point of acupuncture are essential for the analgesic and therapeutical effects of acupuncture. In this study, we measured multiple biosignals (electroencephalogram: EEG), finger photo plethysmogram, respiration, skin temperature and skin impedance) when the needle was inserted into the acupoint called “Hegu, LI₄” to examine how the physiological and psychological condition changed during acupuncture. As a result, it was confirmed that the physiological and psychological state of the subjects became more relaxed for some minutes after the beginning of acupuncture, when the needle was at the right acupoint and there was Deh-chi. Deh-chi was reflected as a remarkable variation in EEG and skin impedance. These results suggested the possibility of establishing an objective evaluation method of the therapeutical effect of acupuncture by quantifying the changes in EEG and skin impedance.

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