Yuji Higashi

Quantitative evaluation of movement using the timed up-and-go test

In this study, the combined use of an accelerometer and rate gyrosensor to identify the activity phases of the timed up-and-go test (TUG-T) was proposed. Measurements during clinical rehabilitation of hemiplegic patients have been attempted using a triaxial accelerometer to measure the activity objectively, which allows a quantitative evaluation. A waist gyrosensor is useful for measuring the postural displacement with high accuracy. By using both the accelerometer and gyrosensor signals, it was possible to detect the activity phases, which were similar to those observed by the therapists. In addition, the walking activity was extracted from the TUG-T, and the RMS value and CV from the acceleration were calculated in every walking cycle. A qualitative difference between the subjects who could walk independently and those requiring supervision was revealed.

Fractal dynamics of body motion in patients with Parkinson's disease

In this paper, we assess the complexity (fractal measure) of body motion during walking in patients with Parkinsons disease. The body motion of 11 patients with Parkinsons disease and 10 healthy elderly subjects was recorded using a triaxial accelerometry technique. A triaxial accelerometer was attached to the lumbar region. An assessment of the complexity of body motion was made using a maximum-likelihood-estimator-based fractal analysis method. Our data suggest that the fractal measures of the body motion of patients with Parkinsons disease are higher than those of healthy elderly subjects. These results were statistically different in the X (anteroposterior), Y (lateral) and Z (vertical) directions of body motion between patients with Parkinsons disease and the healthy elderly subjects (p < 0.01 in X and Z directions and p < 0.05 in Y direction). The complexity (fractal measure) of body motion can be useful to assess and monitor the output from the motor system during walking in clinical practice.

An ambulatory fall monitor for the elderly

Prevention of falling during walking or transfer is important for maintaining quality of life in the elderly. Analysis of falls among the elderly is useful not only for preventing falls, but also for detecting disease in its early stage. The aim of this study is to develop an ambulatory monitor that records falling time. The system consists of a fall sensor, a sensor driver circuit, a microprocessor and a real-time clock. A photo-interrupter is used as the fall sensor because it does not require an electrical switch. The photo-interrupter outputs a trigger signal when the subject is falling and the microprocessor records the falling time. To minimize the power consumption, the photo-interrupter is driven with pulse current, and the microprocessor that records falling time is only operated when the subject is falling. The system works continuously for one week. In this preliminary study, the system was tested for normal adults and hemiplegic patients, and operated without any trouble. Using this ambulatory system, we can obtain data about falling over a long period.

A gait abnormality measure based on root mean square of trunk acceleration

BackgroundRoot mean square (RMS) of trunk acceleration is seen frequently in gait analysis research. However, many studies have reported that the RMS value was related to walking speed. Therefore, the relationship between the RMS value and walking speed should be considered when the RMS value is used to assess gait abnormality. We hypothesized that the RMS values in three sensing axes exhibit common proportions for healthy people if they walk at their own preferred speed and that the RMS proportions in abnormal gait deviate from the common proportions. In this study, we proposed the RMS ratio (RMSR) as a gait abnormality measure and verified its ability to discriminate abnormal gait.MethodsForty-seven healthy male subjects (24–49 years) were recruited to examine the relationship between walking speed and the RMSR. To verify its ability to discriminate abnormal gait, twenty age-matched male hemiplegic patients (30–48 years) participated as typical subjects with gait abnormality. A tri-axial accelerometer was attached to their lower back, and they walked along a corridor at their own preferred speed. We defined the RMSR as the ratio between RMS in each direction and the RMS vector magnitude.ResultsIn the healthy subjects, the RMS in all directions related to preferred walking speed. In contrast, RMSR in the mediolateral (ML) direction did not correlate with preferred walking speed (rs = -0.10, p = 0.54) and represented the similar value among the healthy subjects. Moreover, the RMSR in the ML direction for the hemiplegic patients was significantly higher than that for the healthy subjects (p < 0.01).ConclusionsThese results suggest that the RMSR in the ML direction exhibits a common value when healthy subjects walk at their own preferred speed, even if their preferred walking speed were different. For subjects with gait abnormality, the RMSR in the ML direction deviates from the common value of healthy subjects. The RMSR in the ML direction may potentially be a quantitative measure of gait abnormality.

Unconstrained monitoring of body motion during walking

Discusses using the matching pursuit algorithm to characterize time-frequency patterns of body motion in poststroke hemiplegic patients. We have been working on the quantification of body motions in healthy young and elderly subjects, patients with Parkinsons disease (PD), and poststroke hemiplegic (PSH) patients using an accelerometry technique and advanced signal processing methods. In this article, we use the matching pursuit (MP) algorithm to characterize the time-frequency patterns of the acceleration signal recorded from both healthy subjects and poststroke hemilpegic patients. The MP algorithm was chosen since it provides better time and frequency resolutions than other time-frequency analysis methods and is an algorithm that decomposes any signal into several already-known time-frequency patterns, which are called atoms. It also provides detailed information about each time-frequency pattern including its energy, time and frequency localization, and phase and scale (time duration), which can be used for the comparison and the statistical analysis.

Fractal dynamics of body motion in post-stroke hemiplegic patients during walking

In this paper, we quantify the complexity of body motion during walking in post-stroke hemiplegic patients. The body motion of patients and healthy elderly subjects was measured by using the accelerometry technique. The complexity of body motion was quantified using the maximum likelihood estimator (MLE-) based fractal analysis methods. Our results suggest that the fractal dimensions of the body motion in post-stroke hemiplegic patients at several Brunnstrom stages were significantly higher than those of healthy elderly subjects (p < 0.05). However, in the hemiplegic patients, the fractal dimensions were more related to Brunnstrom stages.

Assessment of gait parameter in hemiplegic patients by accelerometry

A portable microprocessor-based data acquisition system was used to measure the acceleration of joints during walking in ambulatory subjects and to evaluate temporal and spatial parameters of the gait. The system consists of two triaxial accelerometers and a microdata logger with removable memory. After examination, the recorded data are downloaded to a personal computer to analyze the gait cycle, power spectrum, and attractor of two sites. Experiments were performed on 28 hemiplegic patients of different Brunnstrom stages (Br. stages). The orthogonal accelerations at the head of the fibula were measured when walking at a normal speed. The gait cycle for a subject of a low Br. stage was significantly larger than that for a high Br. stage. The frequency distribution of gait for a low Br. stage subject was significantly smaller than that for a high Br. stage. The attractors of normal subjects and unaffected sites were simple figures with small variance, while those of affected sites were complex forms with large variance. The attractor changes simple form with higher Br. stage. Thus, the authors could estimate the rehabilitation effect from the attractor. This monitor may permit a quantitative evaluation of the recovery of paralyzed patients, both in hospital and at home.

A fully automated health-care monitoring at home without attachment of any biological sensors and its clinical evaluation

Daily monitoring of health condition is important for an effective scheme for early diagnosis, treatment and prevention of lifestyle-related diseases such as adiposis, diabetes, cardiovascular diseases and other diseases. Commercially available devices for health care monitoring at home are cumbersome in terms of self-attachment of biological sensors and self-operation of the devices. From this viewpoint, we have been developing a non-conscious physiological monitor installed in a bath, a lavatory, and a bed for home health care and evaluated its measurement accuracy by simultaneous recordings of a biological sensors directly attached to the body surface. In order to investigate its applicability to health condition monitoring, we have further developed a new monitoring system which can automatically monitor and store the health condition data. In this study, by evaluation on 3 patients with cardiac infarct or sleep apnea syndrome, patients’ health condition such as body and excretion weight in the toilet and apnea and hypopnea during sleeping were successfully monitored, indicating that the system appears useful for monitoring the health condition during daily living.

Metabolic changes in the brain of patients with late-onset major depression

Positron emission tomography (PET) with fluorodeoxyglucose-F18 was used to examine glucose metabolism in patients with late-onset major depression, all hospitalized non-responders to antidepressant medication. The three-dimensional stereotactic surface projection (3D-SSP) method provided 3D-SSP images and relative metabolic values with minimal partial volume effects. The 3D-SSP score map showed decreased relative metabolism in the prefontal, cingulate and parietal regions in both hemispheres, and in the temporal region on the right, and increased relative metabolism in the occipital pole, vermis, cerebellum, dorsal-frontal, central convexity areas and basal ganglia in both hemispheres in patients compared with controls. The ratio of the parietal to occipital values in right plus left hemispheres was significantly decreased. Correlation coefficients of the anterior cingulate-primary sensorimotor, posterior cingulate-primary sensorimotor and occipital-media frontal in both hemispheres, of the frontal-primary sensorimotor, occipital-parahippocampal, primary visual-medial frontal and parahippocampal-amygdala in the right, and the frontal-vermis, parietal-thalamus, temporal-vermis, occipital-putamen, primary visual-putamen, thalamus-vermis and thalamus-cerebellum in the left were significantly different in patients compared with controls. Patients with late-onset depression who were treatment non-responders showed alterations not only in limbic-cortical circuits, but also in a wider network of thalamo-cortical circuits.

Dysfunctional Cortical Connectivity During the Auditory Oddball Task in Patients with Schizophrenia

Background: We studied the imaginary coherence (IC) of gamma frequency oscillations between brain regions of male schizophrenia patients during an auditory oddball task using magnetoencephalography (MEG) and electroencephalography (EEG). Methods: Subjects were 10 right-handed male schizophrenia patients, evaluated by the positive and negative symptom scale (PANSS), and 10 healthy controls. Functional connectivity during the auditory oddball task was reconstructed in low (30-50 Hz) and high (50-100 Hz) gamma bands, and represented by imaginary coherence (IC) based on significant oscillatory power changes. We calculated correlations between PANSS scores and IC. Results: In the high gamma band, IC between left occipital and right prefrontal lobe areas during the time window 750-1000 ms from stimulus onset showed negative correlations with total negative scores, total positive scores, the sum of positive and negative scores in PANSS, conceptual disorganization, and social avoidance scores. In the low gamma band, IC between the same areas from 250-500 ms also showed a negative correlation with the conceptual disorganization score. In the same time window, IC between left occipital and right frontoparietal lobe areas in the low gamma band showed a positive correlation with hallucinatory behavior; IC between right temporal pole and left prefrontal lobe areas showed a positive correlation with delusion scores, although these ICs were decreased relative to controls. Conclusions: Functional disconnection of high and low gamma bands in auditory oddball task may play an important role in the auditory processing in schizophrenia patients.