Yuichi Shimatani

Long-term recordings from afferent taste fibers

The receptor cells of taste buds have a life span of about 10 days but it is not known if response characteristics of these receptors alter during the turnover cycle. To examine taste cell responses over time, a micromachined polyimide sieve electrode array was implanted between the cut ends of the rat chorda tympani nerve, which then regenerated through the electrode array. Long-term stable recordings from regenerated single afferent fibers innervating taste buds were possible using this technique for up to 21 days. Responses to taste stimuli recorded from the same fiber changed with time. The changes occurred in both the magnitude of response and the relative response profiles to four chemical stimuli, NaCl, sucrose, HCl, and quinine HCl. These changes in response characteristics were hypothesized to result from changes in the taste receptor cells as the receptor cells turnover in the taste buds.

Application of Near-field intra-body communication and spread spectrum technique to vital-sign monitor

As a novel vital sign monitor, we have developed wireless ECG monitoring system with Near-field intra-body communication technique. However, communication reliability is not so high because transmission channel is noisy and unstable. In order to improve the problem, we utilize spread spectrum (SS), which is known as robust communication technique even through poor transmission channel. First of all, we evaluated characteristics of human body to SS signal. The results show that SS can be used even through human body. Based on this result, we developed and tested near-field intra-body communication device enhanced by SS. The test result shows that SS can solve the problem mentioned above.

Individual identification with high frequency ECG : Preprocessing and classification by neural network

In this research, we proposed that high frequency component of HFECG was applicable biometric feature for new identification system. We developed identification method by using neural network (NN), and aimed at the improvement of the classification rate. Preprocessing prior to NN is performed by justification on time axis and normalization on amplitude. As a result, an average of 99% classification rate was obtained from 9 subjects. We also made an attempt to identify in shorter time by shifting of the HFECG by a few samples to NN.

Central orexin inhibits reflex swallowing elicited by the superior laryngeal nerve via caudal brainstem in the rat.

We examined the effects of orexins on the reflex swallowing using anesthetized rats. Orexins were administered into the fourth ventricle. Swallowing was induced by repeated electrical stimulation of the central cut end of the superior laryngeal nerve (SLN) and was identified by the electromyogram lead penetrated the mylohyoid muscle through bipolar electrodes. The frequency of swallowing during the electrical stimulation of the SLN decreased after the administration of orexin-A in a dose-dependent manner. The latency of the first swallowing tended to be extended after the administration of orexin-A. The administration of orexin-B did not affect swallowing frequency. Pre-administration of SB334867, an orexin-1 receptor antagonist, attenuated the degree of inhibition of swallowing frequency induced by the administration of orexin-A. To identify the effective site of orexin-A, the effect of a microinjection of orexin-A into the dorsal vagal complex (DVC) was evaluated. Orexin-A was injected into one of the lateral DVC, the intermediate DVC, or the medial DVC. Microinjection of orexin-A into the medial DVC but not the other two sites decreased swallowing frequency. Pre-injection of SB334867 into the medial DVC disrupted the inhibitory response induced by fourth ventricular administration of orexin-A. The electrical lesion of the commissural part of the NTS, but not ablation of the AP, abolished the inhibition of reflex swallowing induced by fourth ventricular administration of orexin-A. These results suggest that orexin-A inhibits reflex swallowing via orexin-1 receptors situated in the commissural part of the NTS and/or its vicinity.

Improvement of temporal resolution in blood concentration imaging using NIR speckle patterns

In the imaging of blood concentration change using near infrared bio-speckles, temporal averaging of speckle images is necessary for speckle reduction. To improve the temporal resolution in blood concentration imaging, use of spatial averaging is investigated to measured data in rat experiments. Results show that three frames in temporal averaging with (2×2) pixels in spatial averaging can be accepted to obtain the temporal resolution of ten concentration images per second.

Measurements of blood flow and hemoglobin concentration change in anesthetized rat using two-wavelength laser speckle imaging

We measured simultaneously blood flow and hemoglobin concentration change in the exposed area of an anesthetized rat using laser speckle patterns acquired at two wavelengths. Blood flow was successfully analyzed in a frame rate. Changes of oxy- and deoxy-hemoglobin concentrations were temporally measured. These results indicate the usefulness of the method.

Application of near-field intra-body communication and spread spectrum technique to vital-sign monitor evaluation of error rate in ambulatory status

As a novel vital sign monitor, we have developed wireless ECG monitoring system with Near-field intra-body communication (NF-IBC) technique. However, it was hard to ensure communication reliability because transmission channel is noisy and unstable. In order to improve the problem, we utilize spread spectrum (SS), which is known as robust communication technique even through poor transmission channel. In previous study, we have already developed an ECG monitor using NF-IBC enhanced by SS. In this paper, we evaluated bit error rate (BER) of the system devices in ambulatory status of the user such like walking. The test result shows that communication reliability depends on walking speed. However, it was found that reliability was high enough for practical use. These results indicated that the wireless monitor based on SS NF-IBC was applicable to unrestrained vital-sign monitor.

A study on reception electrodes for the vital-sign monitor using near-field intra-body communication enhanced by spread spectrum technique

As a novel vital sign monitor, we have developed wireless ECG monitoring system with Near-field intra-body communication (NF-IBC) technique. However, it was hard to ensure communication reliability because transmission channel is noisy and unstable. In order to solve the problem, we utilize spread spectrum (SS), which is known as robust communication technique even through poor transmission channel. In previous study, we have already developed an ECG monitor using NF-IBC enhanced by SS. In this paper, we evaluated on structure of the reception electrode for reliable communication. Based on the evaluations with bit error rate, we suggested the reception electrode structure which can keep the communication reliability. As the results we considered that we can expand the reception electrode up to 2.25m2. Moreover, we proposed the structure of the reception electrodes that can keep the communication reliability. Finally we suggested how to use the SS NF-IBC vital-sign monitor in room that larger than 2.25m2, and we had shown the practicability of the systems.

Measurement of Contractile Activity in Small Animal's Digestive Organ by Carbon Nanotube-Based Force Transducer

A carbon nanotube (CNT)-based force transducer designed to be embedded in the body of a live animal was fabricated and implanted into the stomach of a rat omit to measure contractile movement. The transducer comprised dispersed poly(ethylene glycol)-grafted multiwalled CNTs applied to a comb-like Au-electrode formed on a poly(dimethylsiloxane) sheet. The implanted rat was injected with acetylcholine to induce muscular contractions and changes in the resistance of the transducer were measured. Such changes arise owing to strain in the CNT network upon distortion. The measured resistance change was found to be proportional to the concentration of injected acetylcholine.

Estimation of individual response in finger blood concentration change under occlusion on human arm using speckle patterns

We have developed the method for imaging blood flow and blood concentration change by using laser speckle in fiber illumination. We experimentally discuss the relationship of blood occlusion condition and individual response of blood concentration change measured by the method.