In order to understand human motor function, it is necessary to clarify how humans achieve adaptive motions regarding to external environment or their own purpose. This study analyzes human standing-up motion in different chair seat heights and motion speeds using muscle synergy analysis to find important modules to achieve the movement. Muscle synergy is determined from measured eight muscle activations (n=10), and relationship between muscle synergy and body kinematics is clarified. As a result, invariant three muscle synergies were found in human standing-up motion regardless of different seat heights and motion speeds. On the other hand, amplitude and duration of time-varying activation of muscle synergies were properly adujusted to enviromental change. Moreover, it was observed that time-varying activations were strongly corresponded to characteristic kinematic event of standing-up motion. This result implies that humans can achieve the adaptive standing-up motion mainly by controlling time-varying activation of three muscle synergies.
In Japan, number of nursing facility users who require high nursing care level is increasing every year. The previous study was showed that “meal assistance” was the most difficult care technique for the nursing care staff. In this study, a swallowing sensor was developed to reduce burden of nursing care staff for meal assistance. The electromyogram and acceleration of the digastric muscle was measured both at the resting and at the time of swallowing, and evaluated the time of swallowing by computing an integrated root mean square of electromyogram (iERMS) and that of acceleration (iARMS). Eight healthy males swallowed 2 g or 10 g of pudding, respectively. iERMS and iARMS at the time of swallowing were significantly larger than those at the resting, respectively. Elderly people in a special elderly nursing home also ate their lunch, and iERMS and iARMS were obtained. iERMS and iARMS at the time of swallowing were also significantly larger than those at the resting.
Sensor systems have been developed that can automatically obtain physiological data in bathrooms and toilet stalls. In order to measure the physiological data of individuals who live with a number of other people, each person has to be identified separately. However, it is difficult to obtain active user cooperation. Ideally, personal identification should be achieved without requiring subjects to cooperate. Therefore, we measured changes in the load and trajectory of the center of foot pressure when opening a door by utilizing the features of a Nintendo® Wii balance board as a load sensor. We calculated the Euclidean distance between the registered data and the test data. Personal identification was achieved by using the nearest neighbor algorithm. Data generated while walking through a door were obtained for five subjects, yielding an identification rate of 93.7%.
We report the results of a preliminary trial to visualize a cell during freezing process using microscopic electrical impedance tomography (micro-EIT). A printed circuit board was developed for micro-EIT with two measurement chambers, 5mm in diameter and 1.6mm in depth. These chambers were filled with ethanol (2mS/cm) which was then kept at -30°C by placing it on a copper block filled with liquid nitrogen and by using a heater with a programmable controller. A grain of Citrus Sudachi and an egg of Cypselurus Agoo Agoo were placed into the measurement chamber and were recorded data during freezing by using a CCD microscope and micro-EIT. When the sample started freezing, the brightness of the sample became higher and the relative impedance in micro-EIT image also increased. Similar results were obtained in all the four trials respectively. Therefore, these results indicate that EIT is useful to observe freezing process of a cell.
We developed a photoplethysmographic (PPG) linear sensor to obtain PPG signal in the condition of rest sitting with subject's clothes on. The linear sensor is composed of eight-LEDs and eight-phototransistors. The PPG signals were obtained via the clothes by a high brightness of LED pulse. Electrocardiogram and PPG were simultaneously obtained from 10 healthy young males. The relationship between heart rate and pulse rate in 2383 beats were analyzed and no significant differences were obtained in the mean intervals and the standard deviation of intervals.
We developed a prototype of a multi-channel current stimulator chip that can be connected to high-impedance neural stimulating electrodes was designed and fabricated by utilizing 0.25µm high-voltage CMOS technology. The chip consists of five current buffers for the line-parallel multi-channel outputs and multiple registers for setting the stimulation parameters, enabling a multiplexed stimulation with up to 20 channels per chip. The current buffer was designed to generate biphasic pulses with the maximum amplitude of ±100µA. We demonstrated that the current pulses generated by our chip were able to be delivered to the mammalian brain in-vivo.
We investigated the relationship between the green auto-fluorescence (GAF) and the spontaneous electro-encephalographic signals (EEG) recorded from the neocortex of mice under urethane anesthesia. Power spectral density analysis showed that both the GAF and the EEG have a significant activity in the delta frequency band (0.5-1Hz). Cross-correlation analysis and coherence analysis revealed that the GAF and the EEG were correlated in the delta frequency band. These results suggest that the delta frequency component of GAF would be useful to study the spontaneous activity of the neocortex. Visualization of the spatio-temporal dynamics of the GAF delta activity revealed complex phenomena such as propagation of the localized activity and disappearance of the activity after collision. These data suggest the usability of GAF for investigation of the delta activity.
In recent years, the applications of an idea on muscle synergies have been increasing in terms of a coordinated muscle activities for motions. However, a few studies have discussed the relationship between muscle synergies and dynamic motions. We examined the relationship for squatting, pedaling, and ski turning that have the different reproducibility. Furthermore, we discussed the influence of muscle fatigue on muscle synergies. As a result, the robustness of muscle synergies are different depending on the degree of reproducibility of motions and the synergy profiles and weights are effective to identify the small number of muscles that should be measured. Nevertheless, muscle synergies should be further studied regarding the assessment of muscle fatigue with the ling-term trend and fatigue-related changes in muscle coordination.
We propose an algorithm to estimate the shape of the thoracic cavity using curvature sensors. Eight measurement points of curvature were identified and the thoracic shape was estimated using the proposed algorithm from this eight point curvature data. To compare these estimated shapes with those obtained from the CT images, we calculated eccentricity values ‘e’ in seven patients. The mean error in ‘e’ in these seven patients was 13.6%, indicating that the estimated shapes did not match well with the CT data. These results indicate that we may need to increase the number of curvature sensors as well as further refine our algorithm. However, we consider that due to its simplicity and ease of incorporation into EIT firmware, the proposed algorithm can be used in wearable EIT.
This paper evaluated a bed occupancy monitor system, which we proposed previously. In particular, the validity of the system was investigated using testing data. The system, employing capacitively coupled electrodes, converts change in load into change in capacitance. The capacitor was involved in a CR oscillation circuit, and the change is finally converted into voltage using a frequency-voltage converter. The results of the investigation revealed that the accuracy of the algorithm for the system was greater than 90% for three conditions: no occupation, sitting and lying on the bed.