Ocular microtremors are known to be closely related to brain function and physiological states such as arousal, and measuring such microtremors may allow noninvasive brain function measurement. However, the differences between left and right eye microtremors have not been studied in detail. To analyze the differences between left and right eye movements, we developed a binocular microsaccade measurement system that simultaneously records the movements of both eyes at 800Hz. We used the system to examine five healthy male volunteers while performing a one-point fixation task for 30 seconds, and evaluated microsaccades using a formula that represents the difference between the left and right eye movements. As a result, we found several characteristics of the microsaccades. There was no left-right difference in the number of microsaccades, and the left-right difference in the time to reach peak velocity was less than 2.5ms. The results suggest that the difference in microsaccade direction at the time of peak velocity may indicate brain dysfunction and brain activities such as arousal. Additionally, the amplitude of the microsaccades may be regarded as a quantitative personal index of the subject.
A support system for clothes selection by oneself is necessary as a psychological support to help the visually impaired to live independently and be able to socialize. We previously developed an environmental light utilization system in which a smartphone used the light of an indoor environment for illumination. However, for correct color recognition, it was necessary to photograph the clothes with color-rendering indexes (references:color standards) by a smartphone camera, and then correct the colors using appropriate numerical formula for adjusting colors suitable for the illumination conditions. In this study, we developed a novel technique that allows correct color recognition using only a smartphone without the references. In the new system, we used a flash light as the dominant source of illumination, and we developed a numerical formula for adjusting colors which allows correct color recognition even when the indoor light environment changes. We confirmed the precision of color recognition by experiments. Good color difference between 5 and 7 was obtained in the CIE1976 L*a*b*color space. In addition, colors and patterns on clothes were output almost precisely by sounds in experiments on subjects. The results were evaluated on a four-grade scale (between 0 and 3), and average scores of color recognition and pattern recognition were 2.34 and 2.58, respectively. The present results demonstrate that this system is very effective to support visually impaired persons in clothes selection. The use of this system is expected to be widespread in the future because it does not require references.
Knee joint injuries frequently occur in individuals performing sport activities. Knee taping is found to reduce the burden on knee ligaments, particularly the patellar tendon. However, methods for quantitative verification of the kinetic effects of taping on the patellar tendon are limited. In this study, a measurement method using ultrasound imaging was developed to quantify the effects of knee taping on the patellar tendon, and the effects were verified in healthy subjects. The experiment was conducted under five conditions:no taping on the knee joint and taping by four different methods. To verify the differences in taping effect on the patellar tendon under five experimental conditions, we calculated the stress-strain curve from the cross-sectional area and elongation of the patellar tendon acquired using ultrasound imaging. Twelve healthy men (aged 22.6±1.1 years) participated in the experiment. Each subject was asked to sit on a chair with the knee joint flexed at 90°, extend the knee joint, and maintain the extension force for 3 s. During the last isometric contraction, the extension force was changed from 40, 80, 120, 160N to the maximum voluntary extension force of each subject. We succeeded to measure the elastic modulus of the patellar tendon under knee taping condition. The stress-strain curve under no taping condition was significantly different from all four taping conditions (p<0.05).
The surround of a visually recognized target modulates visual recognition. Surround modulation is stronger in the periphery than in the center of the visual field. A previous study of the early visual cortex of cats showed that surround modulation is stronger in the cortical regions corresponding to the periphery of the visual field than in those corresponding to the center. To date, the neural mechanisms underlying surround modulation is poorly understood. In the present study, an electrode array with 5×5 recording points was inserted into the cortex corresponding to the peripheral visual field. In this manner, the spiking activities of the neurons responding to the center and to the periphery of the stimulus were recorded. Two types of visual stimuli were used:(1)center-surround stimuli with a center spot of 5° diameter and a differently controlled grating in the periphery, and(2)full-field stimuli with a uniform grating. Cross-correlations of the spikes were analyzed in a total of 436 cell pairs, and 26 pairs correlated significantly. Significance was defined as a cross-correlation value exceeding 5 SD of the mean values between time lag of ±25ms and ±50ms. Of these 26 pairs, 11 showed significant cross-correlation in response to center-surround stimuli, but not to full-field stimuli. Time lag of the significant cross-correlation indicated the direction of information flow between the neurons. In 8 of the 11 pairs, the information flow was directed from the periphery to the center of the stimuli, and in 3 pairs from the center to the periphery. Of the 11 pairs, 5 pairs showed time lag of 1-5ms and fewer pairs showed time lag of <1ms, 5-10ms and >10ms. These results suggest that the information flow caused by center-surround stimuli is detectable using multichannel recording electrodes and analysis of cross-correlation of spiking activities originating from single neurons.
Recently, magnetic particle imaging (MPI) has gained attention as a new medical imaging diagnosis technology. In MPI, an image is reconstructed by detecting the signals from magnetic nanoparticles (MNPs) injected into the body. Since MNPs have the property of accumulating in cancer cells, MPI is expected to be applicable to early diagnosis of cancer. The fundamental method of MPI involves reconstructing the MNP distribution by detecting the odd harmonics generated from MNPs. However, this method has a problem in that image blurring and artifacts occur due to signals from MNPs outside the signal detection region. In order to resolve this problem, a reconstruction method based on solution of the inverse problem has been proposed. This method suppresses image blurring and artifacts by considering the signals from MNPs outside the target measurement region. However, this method requires huge matrix operation and thereby increasing reconstruction time. In this paper, we propose a new image reconstruction method with orthonormal basis calculated using singular value decomposition. The system function and the observed signals from the distribution of unknown MNPs, which are used for image reconstruction, are expanded using the orthonormal basis. Since the proposed method has a reduced matrix size compared with the conventional solution of the inverse problem, image reconstruction time can be reduced. By numerical simulation, we confirmed that image reconstruction with an image quality equivalent to that of the conventional solution of the inverse problem was obtained in 1/39 calculation time for a 11×11 matrix size image.