A method to evaluate rider's mental and physical workloads (MPWL) using R-R interval (RRI) was studied and proposed. The RRI of 4 subjects riding a motorcycle over 400km was measured and compared with that of the non-riding day, and the relation with MPWL based on subjective evaluation was discussed. While the average RRI of 5 minutes duration, defined as RRM, is a statistic which would reflect MPWL, the effect of circadian rhythm is not negligible, and therefore RRM in long-term riding should be adjusted by the RRM in the non-riding day so as to reflect the rider's MPWL more clearly. The standard deviation of RRI reflects not only short-term RRI variability but also trend of RRI caused by transient change in tension. Thus, it is not suitable for describing tonic states such as rider's MPWL which is reflected by short-term RRI variability. To obtain a more robust statistic in relation to this variability, a new statistic named RRV15 was introduced. RRV15 is a statistic which would reflect tonic states, but the tonic states itself could show circadian rhythm, and so it is not possible to estimate pure MPWL directly from RRV15 itself. There was a remarkable tendency during the riding test for RRV15 to gradually decrease while riding and to recover quickly while taking a rest. Accordingly, a new statistic, RER, referred to as the Recovery Ratio, was defined to quantify recovery performance from the MPWL due to riding. This was an attempt to estimate the MPWL level from recovery performance in RRV15, and was confirmed to agree quite well with the subjective evaluation of MPWL in riding. This method does not require compensation with the non-riding day, and is believed to be practical and useful in evaluation the actual MPWL level in practical circumstances such as operating a vehicle.

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In order to investigate neuronal activities related to binocular rivalry (BR), we have studied spatio-temporal characteristics of EEG rhythmic activities and event-related-potentials (ERPs) elicited by the switching from binocular fusion (BF) to BR and vice versa. EEGs were measured and analyzed at 20 electrode positions over the entire head in nine healthy subjects. The variance of EEGs in the α band (8-13Hz) was attenuated largely in the occipital, posterior-temporal and parietal regions and the minimum variance was observed at 727ms (P₃) after the switching from BF to BR (F to R). Subsequently the variance was recovered slightly. On the other hand, the variance in the α band recovered largely after the slight attenuation until 719ms (P₃) in the alternation from BR to BF (R to F). In the steady state of BR before the switching of the stimuli, the variance in the α band was significantly smaller than the one in BF (paired t-test, n=9, p<0.01). A similar attenuation and recovery of variance in the β band (16-24Hz) was observed in the parietal and central regions. A prominent late negative component peaking at about 500ms was observed in the parietal region in the ERPs elicited by the switching from R to F and from F to R. The amplitude of the late negative component in R to F was significantly smaller than that of F to R (n=9, p<0.01). Therefore, it is possible to interpret that the difference of the late negative component and attenuation of variance in the α band reflects neural activities related to the perception of pattern alternation and the difference of variance in steady state in the α band reflects the difference in the neural activities involved in BR and BF.

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This paper presents an automatic extractiton method of soft tissues from 3D MRI images of the head. A 3D region growing algorithm is used to extract soft tissues such as cerebrum, cerebellum and brain stem. Four information sources are used to control the 3D region growing. Model of each soft tissue has been constructed in advance and provides a 3D region growing space. Head skin area which is automatically extracted from input image provides an unsearchable area. Zero-crossing points are detected by using Laplacian operator, and by examining sign change between neighborhoods. They are used as a control condition in the 3D region growing process. Graylevels of voxels are also directly used to extract each tissue region as a control condition. Experimental results applied to 19 samples show that the method is successful.

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Indocyanine green (ICG) is used for clinical tests, such as liver function, by means of the absorption property in near infrared light. ICG also emits near infrared fluorescence when it is excited with near infrared light. In the present study, we compared fluorescence imaging and absorption imaging of ICG using a simple imaging system composed of CCD (charge coupled device) camera and a Xenon lamp with optical filters. ICG dissolved in DMSO was injected into polyethylene tube penetrated into the head of mice at various depths. At 2 to 4mm depth from the surface of the head, the location of a piece of ICG tube was clearly detected through skin, skull bone and brain tissue by means of fluorescence imaging. In contrast, absorption imaging did not identify the shape of ICG tube nor a syringe needle at 2mm depth, indicating that the failure of identification of ICG by absorption imaging was not due to insufficiency of absorption of near infrared light. These results demonstrate that near infrared fluorescence imaging exceeds in detectability of ICG in biological tissues compared with near infrared absorption imaging. In addition, the ICG fluorescence imaging does not require intricate imaging system, such as computed tomography, when applied to detection of ICG near the surface of biological tissue.

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In the implantable functional electrical stimulation (FES) system, the electromagnetic induction was used to make the implanted stimulator be powered and controlled externally. This could lead to disturb transmitted stimulus data from the external unit to the implanted stimulator by environmental electromagnetic noise. As one of fail-safe methods to improve noise immunity, an application of the error detecting and correcting circuit to the implantable FES system was described. The term “noise immunity” meant the property of a system enabling it to reject influence of an external electromagnetic noise. The circuit was based on the Hamming coding, made high-speed error detection and correction feasible, and allowed hardware simplicity. An encoder and a decoder were incorporated into the prototype FES system. In the evaluation of the noise immunity capability, an electromagnetic noise generator, which was composed of a sinusoidal oscillator and a disturbance coil, was employed. The disturbance coil was moved coaxially and parallel close to the transmitting coil. Then, with varying frequency of sinusoidal wave of the oscillator, an attention was paid to the distance between the transmitting coil and the disturbance coil. The distance where the bit error rate of transmitted data was 2.5×10^-4 was measured in the cases with and without the error correcting circuit (ECC), respectively. The experimental results clearly showed that the system with the ECC was more insensitive to disturbance noise than that without the ECC. The ECC also worked effectively even in the cases of utilizing other electromagnetic disturbances, such as some electric appliances and a 430MHz-band radio ham transceiver. It was concluded that the reliability of transmitted stimulus data would be verified by using the ECC for the implantable FES system.

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Changes in proliferation and physiological reaction of osteoblast-like cells (MC3T3-E1) under a mechanical stress was investigated, and effects of the mechanical stimulation on the function-expression of the cells was evaluated in this study. MC3T3-E1 cells were cultured for four days in a culture dish with α-MEM containing 10% FBS at 37°C under a 5%-CO₂ atmosphere. The effect of mechanical stress on proliferation of MC3T3-E1 cells was evaluated by comparing the number of cells in the dish under stress with that in the control dish. The number of cells was obtained at prescribed area on the dish every day for three days. To explore the response of osteoblast-like cells to the mechanical stress, we observed intracellular Ca²⁺ concentration. Changes in intracellular Ca²⁺ concentration after mechanical stress were evaluated through fluorescence intensity using a confocal laser scanning microscopy. The results led to the following conclusion: (1) Mechanical stress may be a factor that affects the proliferation of osteoblast-like cells, and there must be an optimal condition for proliferation. (2) Osteoblast-like cells may have detecting mechanisms for mechanical stress. (3) Mechanical stress may be a factor regulating function-expression of osteoblast-like cells. The results expect the effects of the mechanical stimulation on the matrix formation of bone tissues although the optimal parameters for the stimulation have not been determined so far.

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Human in vivo sublingual microvessels new observed directly after administrating nitroglycerin (Glyceryl trinitrate; GTN) by our novel needle-type CCD intravital microscope (magnification 200×). Subjects were all healthy and non-smoker volunteers. Hemodynamics were monitored continuously using a non-invasive automatic tonometer at sitting position. After mental and physical relaxation, the control images were taken by making an access of the needle lens probe (diameter; 4mm) onto sublingual microvessels. Then microvascular diameter changes after GTN were monitored for 5min. The images were stored on the videotape with hemodynamic data was transferred to a computer, and the diameter changes of the microvessels were analyzed at end diastole. The microvessels were divided into two groups (arteriole or venule<100μm and small artery or vein≥100μm), because of their possible different responses to nitroglycerin. The sublingual microvessels could be observed clearly in all subjects. The diameter of venules dilated gradually after GTN and its dilatory responses were continued. Small veins dilated, but they exhibited smaller responses than venules. Their maximum dilation was 18±3% and 8±2%, respectively (p<0.05, vs. control). Arterioles showed dilatory responses as seen in venules. Arteriolar and small arteries maximum diameter dilation was 25±4% and 8±4%, respectively (p<0.05, vs. control). In conclusion, the sublingual microvessels were clearly visualized non-invasively by our needle-type CCD intravital microscope. The degree of vasodilation to GTN was higher in venules and arterioles (<100μm) than small veins and arteries (≥100μm) in human. Those vascular changes may be important for reduction both preload and afterload, relieving anginal attack.

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A feedback sway control system of trunk inclination angles was designed to improve the postural stability of paraplegic standing by functional electrical stimulation (FES). The system was constructed of two proportional-and-derivative (PD) controllers and four co-activation stimulation maps. The performance in postural stability was clinically evaluated by applying a step disturbance while a paraplegic subject with spinal cord injury in thoracic 8th level is quietly standing between parallel bars using knee-ankle-foot-orthosis. The decrease of the backward sway magnitude by using the proposed system was statistically significant, when the 10N backward disturbance was applied.

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To Exploring the response of osteoblast-like cells to mechanical stresses, we developed an experimental apparatus which applies mechanical stresses to osteoblast-like cells. The main part of the apparatus is composed of a piezo ceramics and a pulse generator. This apparatus can apply a variety of frequency, amplitude, and wave form of the vibration to the cells. To evaluate the capability of the apparatus, we measured the strain on a culture dish developed by the apparatus. It was shown that control of the strain on the culture dish was possible with the apparatus, and that this apparatus is useful to study the cell reaction to the mechanical stresses.

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One of the important subjects in constructing the computer-aided diagnosis system for detecting breast cancers is to get the knowledge of the diagnostic process when experts diagnose breast cancers by using mammograms. In this study, we investigated the classification logic for the diagnosis of breast masses on mammograms in cooperation with a mommographic specialist. From many features of the masses such as “sharp outline” and “stellate boundary”, we selected 13 features and weighted them by integer values from -1 to 2. The classification was achieved based on the total amount of the weighted values for all features. We tested our classification logic by use of 103 mammograms, and except the very difficult three cases the classification rate for defining the mass as malignant or benign was very high (sensitivity of 84% and specificity of 96%).

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We have developed a portable measurement system for automatic transcutaneous blood-glucose monitoring by adopting the suction effusion fluid (SEF) from human skin as a sample. We applied our newly developed system to the glucose measurement on human subjects. The SEF can be obtainable transcutaneously by sucking human skin of which a corneous layer was stripped. The glucose concentration of SEF has shown good correlation to blood serum. Since the effusion rate of SEF was 5-15μl/cm²/h, the miniature ion sensitive field effect transistor (ISFET) glucose sensor which could repeatedly measure glucose concentration of small volume sample was employed to measure the glucose concentration in the SEF. Our system consists of a main frame (1100g in weight) and a suction apparatus (120g in weight). These apparatus were easily fixed on waist and arm with belts. The unique component devices such as a glucose sensor apparatus and pumps were originally developed to realize the portable automatic glucose measurement system. Our system had been applied to rabbit model to evaluate accuracy of the system. The results had shown that there were good correlation between measurement value of our system and conventional method. We applied this system to human subjects. The glucose concentration in the SEF was automatically measured every 30 minutes for 3 hours. The glucose concentration in the SEF from a different portion of human skin was measured by the conventional method. Blood glucose concentration was also measured. The glucose concentration from our system and the conventional method showed almost the same time-history with ±10% correlation error and 0.916 of correlation coefficient. Since we demonstrated excellent performance of our portable system, this system would be great contribution to human glucose monitoring.

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Single neuron activities from cortical areas of a monkey were recorded while performing a sensory-motor task (a choice reaction time task). Quantitative trial by trial analysis revealed that the timing of peak activity exhibited large variation from trial to trial compared to the variation in the behavioral reaction time of the task. Therefore, we developed a multi-unit dynamic neural network model to investigate the effects of structure of neural connections between cortical areas on the variation of timing of peak activity. Computer simulation of the model showed that, even though several units are connected in cascade fashion, if there is variation in the parameters of neural activity, there exists wide variation in the timing of peak occurrence compare to variation in the reaction time because there are multi-pathways in the neuronal network from the sensory stimulus to the motor response. Analysis of relationship between the amplitude of peak activity and difference of the time variance of peak activity and the time variance of behavioral reaction time suggests that neurons which had high peak activity form part of pathways that were strongly related to triggering the motor response.

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The effect of a burst of temporal pattern stimulation on the induction of long-term potentiation (LTP) was investigated in CA1 neurons of hippocampal slices of guinea-pigs. Three types of statistical stimuli (periodic, normal distributed, and Markovian stimulus) with a single pulse or the burst (4 pulses at 100Hz) for each consisting stimulus were applied to the Schaffer commissural-collateral fibers as temporal pattern stimuli; two factors were independently controlled, one was the burst with a short interval and the other was temporal pattern with long mean intervals. As a result of the experiment, the effect of burst stimulus in the LTP was observed independent of that of temporal pattern stimulus. From the observation, there may be two important time factors for the effective LTP, one is a short duration (20-30ms) and the other is a long-interval duration of the order of several hundreds ms. The both effects were discussed from the point of view of information processing, learning and memory in the hippocampus.

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We proposed a spatiotemporal model of simple cell based on resent physiological findings and indicated its capability of detecting velocity of moving image. The model consists of several simple cells mutually connected and four types of LGN cells (spatial type, on/off center and temporal type, nonlagged/lagged). One simple cell connects to four types of LGN cells which are spatially placed in a form of periodical band. The periodical band is shifted in position among simple cells. The spatial receptive-field profile of simple cell can be approximated to Gabor function and the shift correspond to phase difference of the function. We showed that the model has selectivities in spatial frequency, orientation and velocity of stimulus and the responces agree with the physiological experimental data. Then, we proposed a network consisting of simple cell models of different optimal spatial frequencies and indicated that the network can detect velocity of drifting grating stimuli.

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Various optimal criteria have been proposed for trajectory planning in multi-joint arm movements. The minimum-jerk criterion plans smooth trajectories in the extrinsic task space. The minimum-joint-angle-jerk criterion, the minimum-torque-change criterion, and the minimum-motor-command-change criterion plan smooth trajectories in the intrinsic body space. Assuming that realized trajectories reflect planned trajectories, we compared the values of above four optimal criteria calculated from observed movement data. If the value of a certain criterion is larger in a spontaneously generated movement than in some other movement, that criterion can be rejected. If, however, the value of a certain criterion is smaller in a spontaneously generated movement than in any other movement, it supports that criterion. Subjects were instructed to move their hand to a target passing through a via-point. Several via-points were given randomly to make subjects generate hand paths with various curvatures. The curvatures of the paths that have minimum values of a certain criterion are compared to curvatures of the spontaneously generated paths. The values of hand-jerk and joint-angle-jerk were obtained from measured position data. The values of torque-change were obtained using the dynamics equation of a two-joint arm model with estimated physical parameters. The values of motor-command-change were obtained from quasi-tension calculated from rectified EMG using a second-order low-pass-filter. The minimum-jerk criterion was larger in spontaneously curved movements than in movements with straighter hand paths. This result rejects the minimum-hand-jerk criterion. However, joint angle jerk was not always minimum around the hand paths predicted by the minimum-joint-angle-jerk criterion. Subjects tend to generate trajectories that have lower values of minimum-motor-command-change criterion.

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In multi-joint movements, possible trajectories for a given target are infinite, but actually have certain invariant features. It has been discussed whether trajectories of the human arm are planned in an extrinsic space or in an intrinsic space. Hand paths planned in the former are predicted to be always straight, while those in the latter are generally curved. Both Uno et al. and Osu et al. reported that actual hand paths tended to significantly curve for some specific arm postures, movement distances, and movement durations. We have extended the previous studies by using various initial and final positions located within a workspace and examined if the curvature of a trajectory quantitatively varies with arm posture when subjects make point to point reaching movements on a horizontal plane. Curvatures of measured hand trajectories were linearly estimated using two models, hand position and hand translation, which are represented by extrinsic coordinates, and other two models, joint angle and joint rotation, which are represented by intrinsic coordinates. In experiment I and II, movement durations were restricted, and in experiment III, movement durations were flexible and added to parameters. Movement durations and joint rotation significantly contributed to curvature. We succeeded in predicting the curvature of hand paths by using the arm posture before and after a movement. The results suggest that trajectory curvature depends on arm posture and is in accordance with predictions made under planning in the intrinsic space, rather than that in the extrinsic space. Furthermore, the result that a longer movement duration causes a larger curvature is in agreement with the predictions of Uno and Kawato, in which a longer movement duration makes paths expand toward the outer side because of an effectively larger viscosity ratio.

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Short-term memory (STM) function has an important role for flexible processing of temporal sequence in human auditory system. In this article, we report the results of basic experiments on mismatch response to a change in tone duration. These experiments were executed to obtain findings for elucidating the mechanism for encoding information of time domain and its short-term memory system. In this study, we measured both mismatch negativity (MMN) by electroencephalogram (EEG) and mismatch field (MMF) by magnetoencephalogram (MEG), and investigated properties of duration mismatch response and its relation to the human cognitive processes. Four subjects were measured MMN on the oddball-paradigm experiments, in which successive tones (durations 100, 200, 300 and 400ms) as standard stimuli, and the tones with different durations (60, 70, 80, 90% of the standard ones, other attributes were same as standard ones) as deviant stimuli. We observed the relationship between the amplitude and latency of MMN, and the ratio of the durations of standard and deviant stimuli. It was suggested from these results that the duration mismatch response reflected the properties of discrimination and short-term memory of tone duration. One subject was also measured MMF in the same paradigm by the 64 channel first-order SQUID gradiometer, in which the duration of standard stimuli were fixed to 100ms. As a result, it was confirmed that the properties of the amplitude and latency of duration MMF was almost same as those of duration MMN, and that the estimated current sources of MMF distributed in the auditory cortex and their locations were anterior to those of N100m. The result of MMF recording by the 256 channel whole-head SQUID magnetometer system on one condition is also shown in this article. From this experiment, it was suggested that duration mismatch response is a unique measure for elucidating higher-order brain function, e. g., short-term memory. Such a technique to observe brain activity in a macroscopic way is thought to provide valuable findings to approach to the mechanism of human brain from the systematic sight of view.

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A nonlinear dynamical model of the neuro-musculo-skeletal system that generates pathological gaits is presented. This model was originally proposed to show that the normal gait of humans is generated by the dynamic interaction of the entrainment between the model neural system composed of neural oscillators and the musculo-skeletal system. In this paper, a series of computer simulations demonstrated that asymmetric gaits, irregular and unstable gaits with changing step length and shuffling gaits with small step length are generated by changing various parameters of the neural system or by destroying a part of the neural system. General conditions under which specific patterns of gaits are produced are discussed in relation to the pathological gaits of patients with the hemiplegia, the cerebellar disease and the Parkinson's disease.

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