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Biomedical subjects

Yoshihisa Masakado

Publications and source records attributed to Yoshihisa Masakado.

At least 19 recordsLinked to original sources
PubMed2006

Modulation of the soleus H-reflex during static and dynamic imposed hip angle changes.

The aim of the study was to investigate the modulation of the soleus H-reflex during static and dynamic imposed hip angle changes. Five healthy subjects participated. H-reflexes were measured during hip joint passively flexed and extended in the sagittal plane. In flexion phase, the soleus H-reflex during dynamic conditions was lower than the stationary controls. By contrast, it was conversely higher in extension phase. The findings suggest that the modulation of the soleus H-reflex from hip proprioceptors is a major factor in passive hip movement. Additionally, the central pattern generator might modulate the soleus H-reflex.

Adult↗
PubMed2005

Inhibition from the plantar nerve to soleus muscle during the stance phase of walking.

The purpose of this study is to investigate the effect and the circuit from the branch of tibial (plantar) nerve to soleus muscle and its modulation during walking in humans. Stimulation of the plantar nerve produced short latency inhibition of soleus EMG activity and the H-reflex in humans. The threshold of afferent fibers was lower than that of motor fibers. This inhibition did not converge to disynaptic reciprocal Ia inhibition nor did inhibition from the cutaneous nerve of the big toe, but to Ib inhibition from the medial gastrocnemius nerve. The inhibitory pathway from the plantar nerve therefore is considered to include Ib inhibitory interneurones. Modulation of the inhibition was investigated during walking. Less EMG depression after plantar nerve stimulation occurred in the stance phase of walking than for tonic or dynamic plantar flexion at similar background EMG activity level. The inhibition of the soleus H-reflex after plantar nerve stimulation was also decreased during the stance phase. For investigating the influence of load on the inhibition from the plantar nerve, more EMG depression occurred in the stance phase with body unloading. Similar findings were observed in Ib inhibition from the medial gastrocnemius nerve, but not in disynaptic reciprocal Ia inhibition to soleus muscle. It is concluded that transmission of inhibition from the plantar nerve to soleus muscle is modulated during walking. It would minimize this inhibition during the stance phase of walking and might enhance soleus muscle activity via this reflex pathway for the support of weight.

Adult↗
PubMed2005

Soleus H-reflex modulation pattern for a fine angle of hip and knee joint passive movement.

OBJECTIVE: To elucidate whether hip and knee joint movement modulate soleus H-reflex, the authors measured the soleus H-reflex for a very fine angle during movement. METHODS: Eight healthy subjects participated. The knee and hip joints were passively flexed and extended ranging from 0 degrees to 120 degrees simultaneously. RESULTS: In the flexion phase, H-reflex decreased. It decreased more during fast movement. In the extension phase, H-reflex increased markedly. CONCLUSION: By measuring for a fine angle, it was clearly found that the stretch of the muscles around the knee and hip joints caused the changes in soleus H-reflex.

Adult↗
PubMed2005

Excitability of spinal inhibitory circuits in patients with spasticity.

The excitability of Ia inhibition and D1 inhibition after stimulation of the common peroneal nerve to the soleus motoneuron pool was investigated in 37 spastic patients at rest and onset of voluntary ankle dorsiflexion. Ia inhibition was determined as the short-latency depression of the soleus H-reflex and D1 inhibition as the long-latency depression. There was no significant difference in Ia inhibition between the paraplegic and control groups, however Ia inhibition in the hemiplegic group was significantly decreased. D1 inhibition was reduced in the paraplegic and hemiplegic groups compared with controls. Although inhibition of the soleus H-reflex appeared at the onset of voluntary dorsiflexion in control subjects, it was not observed in the patients. Although the excitability of the Ia inhibitory pathway at rest in the patients did not differ from that in control subjects, facilitation of the Ia inhibitory pathway at the onset of movement was decreased in the patients. Ia inhibition and D1 inhibition were evaluated in two paraplegic patients who were treated with local anesthesia and surgery, respectively. The excitability of both inhibitory pathways at rest was unchanged despite improvement of reciprocal movement in one patient, and was enhanced despite reduction in muscle strength in the other patient. The excitability of spinal inhibitory pathways at rest was not always reflected by motor function in spastic patients.

Adult↗
PubMed2005

Clinical electromyography and electrodiagnosis course at Keio University Hospital--a 7-year experience.

Although electromyography and electrodiagnosis (EMG-EDX) is one of the most fundamental skills in rehabilitation medicine, the number of residency programs that can provide comprehensive postgraduate EMG-EDX training is still limited in Japan. Under these circumstances, we started a 2-day primer course in EMG-EDX at Keio University Hospital in 1998. To review our 7-year experience with the course, we analyzed the number and specialty of the participants, their appraisal of the lectures and practical sessions, and the score distribution of the final examination. The number of participants totaled 288 during the past 7 years, and the mean number for each year was 41. The distribution by specialty for the whole period was 64.0% for rehabilitation medicine, 25.4% for orthopedic surgery, 5.1% for neurology, 1.0% for pediatrics, 0.5% for gerontology and 4.1% for physical therapists and occupational therapists. The difficulty levels of the lectures were judged as appropriate by 81 to 95.5% of the participants, and the presentation was judged as good by 34 to 67% of them. For the practice sessions, the difficulty levels were judged as appropriate by 88% of the participants, and the quality of the supervisors was judged as good by 64% of them. The mean score for the final examination was 56.0 (SD 15.2, median 60). In conclusion, our course has played an important role to promote EMG-EDX in our country by providing compact introductory exposure to EMG-EDX for beginners. A follow-up system for the course graduates is planned to support their EMG-EDX practice.

Diagnostic Techniques, Neurological↗
PubMed2005

[Reflex responses from the sural nerve to tibialis anterior muscle in hemiplegic patients: the relation between the responses and Babinski sign].

Stimulation of the sural nerve of healthy subjects induced short latency inhibition in the ipsilateral tibialis anterior muscle and facilitation in peroneal muscle. We examined lower limb muscle responses after stimulation of the sural nerve in 19 patients with hemiplegia caused by cerebro-vascular disease and compared them with the control responses. The sural nerve was stimulated electrically (3 or 5 square wave pulses of 0.5 ms repeated at 250 Hz) during weak tonic contraction. Stimulation was triggered to average the rectified surface electromyography (EMG) of the test muscle. Usually 100 - 200 sweeps were averaged. After stimulation, the tibialis anterior muscle on the affected side of the hemiplegic patients showed the patterns of inhibition, facilitation, and no response, whereas all responses on the unaffected side, except those of one patient, were inhibition. The peroneal muscle on both sides showed only facilitation as in the controls. Abnormal responses of the tibialis anterior muscle on the affected side were present in many patients who had the Babinski sign. Abnormal responses in the tibialis anterior muscle of the affected side may have been due to contributions by disinhibition of the flexor reflex, late-recruited motor units or both.

Adult↗
PubMed2004

The suppression of the long-latency stretch reflex in the human tibialis anterior muscle by transcranial magnetic stimulation.

The purpose of this study was to investigate the transcortical nature of the long-latency stretch reflex (M3) in the human tibialis anterior muscle. This was achieved by applying a single pulse of subthreshold (90% motor threshold) transcortical magnetic stimulation (subTMS) at the site of the motor cortex. Such a stimulus is able to activate intracortical inhibitory circuits and thereby depress motor cortical output. We hypothesized that it would also suppress a transcortical reflex loop. The stretch reflex was elicited using a pedal attached to an electric motor. SubTMS was applied at several intervals prior to M3. Recordings were repeated 20-40 times. The reflex components were quantified using 20-ms windows in the averaged rectified electromyogram (EMG). SubTMS evoked significantly larger depression of M3 than of the background EMG in the same time frame when applied 55-85 ms prior to M3 ( P<0.05, n=10). Furthermore, the effect on M3 was significantly larger than the effect on the spinal M2 ( P<0.01, n=7). Our results provide evidence that the long-latency stretch reflex in the tibialis anterior muscle is at least partly transcortical.

Adult↗
PubMed2004

Twenty-seven years of complication-free life with clean intermittent self-catheterization in a patient with spinal cord injury: A case report.

Currently, clean intermittent self-catheterization (CISC) is the most prevalent method of bladder management in patients with spinal cord injury (SCI) at discharge from rehabilitation centers. However, half of the patients discontinue using CISC and change to other methods of bladder management several months postdischarge despite the fact that it the best way to prevent urinary tract complications. Few studies, however, report the long-term consequences of CISC. In this case, we present a woman in her early fifties who had sustained thoracic SCI and had continued using CISC for 27 years without developing any complications. The possible reasons for her success were absence of incontinence because of underactive and normal capacity bladder; normal upper-extremity functions and absence of marked spasticity of lower extremities that facilitated CISC technique; and absence of sociovocational problems, enabling her to keep proper intervals between catheterizations each day. This case indicates that CISC is useful for long-term bladder management in patients with SCI, even for 25 years or more. Long-term outcomes of CISC and factors leading to success need to be delineated in future studies with larger samples.

Female↗
PubMed2004

The physiological functional loss of single thenar motor units in the stroke patients: when does it occur? Does it progress?

OBJECTIVE: We examined the time at which loss of functioning motor units occurs on the hemiparetic side, the relationship between that loss and hemiparetic severity, and how long that loss continues. METHODS: Sample surface motor unit action potentials (S-MUAPs) were evoked in F-waves. They entirely represent the activity of the relative numbers of different shape S-MUAPs for each abductor pollicis brevis muscle. S-MUAPs from selected population of F-waves were averaged after aligning onset latency. Motor unit number was obtained by dividing the maximum M-potential negative peak amplitude by the averaged S-MUAP one. RESULTS: The motor unit number on the hemiparetic side was significantly lower than that on the unaffected side in stroke patients who had suffered hemiparesis for more than 9 days. This motor unit loss was greater in patients with severe hemiparesis. One year after onset, the chronic stroke patients showed the same motor unit loss on hemiparetic side as they had 3-4 months after onset. CONCLUSIONS: Motor unit loss on the hemiparetic side is present as early as the second week after onset and is correlated with hemiparesis severity, and this loss continues out to 1 year. This may be due to trans-synaptic degeneration that occurs secondarily to upper motor neuron lesion.

Action Potentials↗
PubMed2004

Development of a new measure to assess trunk impairment after stroke (trunk impairment scale): its psychometric properties.

OBJECTIVE: The purpose of this study was to investigate reliability, validity, internal structure, and responsiveness of our newly developed Trunk Impairment Scale (TIS) for patients with stroke. DESIGN: A total of 73 patients with stroke participated in this prospective study. Interrater reliability (weighted kappa statistics), content validity (principal component analysis), concurrent validity (Spearman's rank correlation with the Trunk Control Test), predictive validity (prediction of discharge FIM scores), and responsiveness (standardized response mean values) were examined. Internal consistency and item difficulties were analyzed with Rasch analysis. RESULTS: The weighted kappa of each TIS item ranged from 0.66 to 1.0. Principal component analysis revealed that the TIS measured a domain similar to the Stroke Impairment Assessment Set trunk items but different from the Stroke Impairment Assessment Set motor and visuospatial items. The TIS correlated with the Trunk Control Test (r = 0.91). To predict discharge FIM motor scores, addition of the TIS as one of the predictors to age, time from onset, and admission FIM score increased the adjusted R2 from 0.66 to 0.75. With Rasch analysis, the misfit was acceptable, except for the abdominal muscle strength item. The difficulty patterns were similar at admission and discharge, except for the abdominal muscle strength item. The responsiveness of the TIS was satisfactory and comparable with that of the Trunk Control Test (standardized response mean values, 0.94 and 1.06). CONCLUSIONS: Our newly developed TIS is reliable, valid, and responsive for use in stroke outcome research.

Adult↗
PubMed2004

Physical fitness in persons with hemiparetic stroke: its structure and longitudinal changes during an inpatient rehabilitation programme.

OBJECTIVE: To test the hypothesis that the structure of fitness in patients with hemiparetic stroke can be categorized into impairment/disability, cardiopulmonary, muscular and metabolic domains, and to study longitudinal changes in their fitness during an inpatient rehabilitation programme. DESIGN: Structure analysis of multiple fitness parameters with principal component analysis (PCA), and a before and after trial. SETTING: Tertiary rehabilitation centre in Japan. PATIENTS: One hundred and seven consecutive inpatients with hemiparetic stroke. INTERVENTION: A conventional stroke rehabilitation programme consisting of 80 minutes of physical therapy and occupational therapy sessions five days a week, and daily rehabilitation nursing for a median duration of 105.5 days. MAIN OUTCOME MEASURES: Principal component scores extracted from measurement of paresis/daily living (the Stroke Impairment Assessment Set (SIAS) and the Functional Independence Measure (FIM)); muscular (grip strength (GS), knee extensor torque, and cross-sectional areas of thigh muscles); metabolic (body mass index (BMI) and fat accumulation on CT); cardiopulmonary (heart rate oxygen coefficient (HR-O2-Coeff) obtained with a graded bridging activity and a 12-minute propulsion distance). RESULTS: PCA categorized the original 15 variables into four factors corresponding to paresis/activities of daily living, muscular, metabolic and cardiopulmonary domains, and explained 78.1% of the total variance at admission and 69.6% at discharge. Except the metabolic domain, PCA scores for the other three domains improved significantly at discharge (paired t-test, p < 0.05). CONCLUSION: The hypothetical structure of fitness was confirmed, and the PCA scores were useful in following longitudinal changes of fitness during inpatient rehabilitation.

Adult↗
PubMed2003

Rehabilitation research from a non-English speaking country published in peer-reviewed English journals--the Japanese experience.

PURPOSE: To study the status of contribution by non-English speaking countries to international rehabilitation literature taking Japan as an example, and to suggest recommendations to overcome the language barrier. METHOD: Descriptive study using a systematic MEDLINE search with outcome measures of annual numbers and proportions of articles by Japanese physiatrists published in peer-reviewed English rehabilitation journals, and of categories and types of studies. A database containing 292 relevant articles were used for analysis. RESULTS: The publications have steadily increased annually both in absolute number and in proportion. The number was the largest for Arch Phys Med Rehabil (16.8%), followed by Am J Phys Med Rehabil (12.3%), Prosthet Orthot Int (8.6%), Disabil Rehabil (5.1 %) and so on. The percentage by category was the highest for stroke (26.0%), followed by spinal cord injury (11.6%), neurophysiology (11.6%) and amputation (6.2%), 67.8% of the articles were related to evaluation, 6.5% to outcome studies and 25.7% to therapy. The majority were descriptive studies (45.5%), followed by case control studies (13.0%), before-and-after trials (12.3%), case reports (7.2%) and others. CONCLUSION: The contribution from Japan to international rehabilitation literature is increasing. Measures were suggested to facilitate more scientific contribution by non-English speaking researchers.

Humans↗
PubMed2003

Reassessment of parameters for applying motor-unit triggered stimuli in peri-stimulus time histograms.

We reassessed the response properties of peri-stimulus time histograms (PSTHs) in cases when a test stimulus was triggered by a motor-unit discharge with a constant delay time. In this experiment, single motor unit action potentials were recorded from the right tibialis anterior (TA) muscle of five healthy persons. A test stimulus of the common peroneal nerve with low intensity to activate only Ia afferents of the TA was applied through a bipolar stimulating electrode placed distal to the neck of the fibula. We obtained several PSTHs with various delay times and stimulus intensities in the same recording session for maintaining the background property as the same among the test situations. As a result, we confirmed three characteristics of PSTHs from observed data: (1) given the same delay time (the same background firing properties), a weaker stimulus intensity evokes a lessened effect on PSTHs, naturally; (2) delay time alters the induction balance of direct and indirect effects on PSTHs even if the stimulus intensity is the same because the background firing properties are different; and (3) response probabilities do not correspond directly to stimulus intensities when background firing properties are different; it is possible for a relatively strong intensity stimulus to produce a weaker effect than a weak stimulus. We concluded that comparisons of effects taken at different phases in the control distribution (and also effects taken from different control distributions or different motor units) can be misleading. Therefore, such comparisons should only be made within data obtained from the same phase in the same control distribution of the same motor unit.

Adult↗
PubMed2003

Long-loop reflex from arm afferents to remote muscles in normal man.

The present study was designed to examine the effects of median nerve stimulation on motoneurones of remote muscles in healthy subjects using H-reflex, averaged EMG and PSTH methods. Stimulation of the median nerve induced facilitation of soleus H-reflex from about 50 ms and it reached a peak at about 100 ms of conditioning-test interval. Afferents that induced the facilitation consisted of at least two types of fibres, the high-threshold cutaneous fibres and the low-threshold fibres. When the effects were examined by the averaged surface EMG and PSTH, no facilitation but rather inhibition or inhibition-facilitation was induced in all tested muscles except for the upper limb muscles on the stimulated side. The inhibition latency was shortest in masseter muscle and longest in leg muscles, while values for the contralateral upper limb muscles were in the middle, indicating that the onset of inhibition was delayed from rostral to caudal muscles. Inputs from the median nerve converged to inhibitory interneurones, which mediate the masseter inhibitory reflex. Our findings suggested that inputs from the median nerve initially ascend to the brain, at least to the brainstem, and then descend to the spinal cord. Therefore, inhibition induced by median nerve stimulation was not considered as an interlimb reflex mediated by a propriospinal pathway, but long-loop reflex, at least via the pons. The discrepancy between the results of reflex and motor units suggests that facilitation of soleus H-reflex following median nerve stimulation was mainly due to reduced presynaptic inhibition.

Adult↗
PubMed2003

Trunk muscles in persons with hemiparetic stroke evaluated with computed tomography.

OBJECTIVES: To analyse side difference in bilateral trunk muscles in patients with hemiparetic stroke, to relate it with impairment and disability variables and to evaluate longitudinal changes. METHODS: In a sample of 83 inpatients with hemiparetic stroke undergoing rehabilitation, we measured the cross-sectional area of the paravertebral muscle and thigh muscles using computed tomography at admission and discharge. Classifying them by paravertebral muscle side difference (group I: contralateral > ipsilateral; II: contralateral = ipsilateral; III: contralateral < ipsilateral) we analysed group difference in the Stroke Impairment Assessment Set, the Functional Independence Measure and walk velocity. RESULTS: In contrast to thigh muscles, the paravertebral muscle cross-sectional area was significantly greater on the side contralateral to the brain lesion. Discharge paravertebral muscle cross-sectional area increased significantly from admission values. The Stroke Impairment Assessment Set, Functional Independence Measure and walk velocity were significantly lower in group I. CONCLUSION: The contralateral paravertebral muscle cross-sectional area was larger than the ipsilateral ones, and this was related to the degree of impairment and functional limitations.

Adult↗
PubMed2003

Formula-based approach of statistical tests for peri-stimulus time histograms.

We introduce formula-based approaches for statistical tests regarding peri-stimulus time histograms (PSTHs) in cases when a conditioning stimulus was triggered by a motor-unit discharge with a constant delay time. The individual bin test and the cumulative sum test have recently been reported as methods for the quantitative analysis of PSTHs in the evaluation of human neural projections. These tests calculate confidence intervals using simulated point processes on the discharge of a motor unit, but require a significant amount of calculation time for the point process simulation. In order to overcome such a disadvantage in practical use, we provide a statistical formulization of the two above-mentioned tests using a combination theory. In general, the time required for calculating confidence intervals using these formula-based approaches was 2-13 times faster than when using the previous approaches. Unlike the previous ones, these formula-based approaches do not need to judge that a simulation process converges to the substationary state, and calculate an ideal distribution of statistical noise on the histogram, thereby providing high accuracy. We conclude that the formula-based approaches increase reliability and are sufficiently sophisticated for practical use.

Action Potentials↗
PubMed2002

Synchronization analysis using joint peri-stimulus time histograms for human motor units.

The concurrence of action potentials from two motor units (MUs) happens more frequently in human than what one would expect by chance. It can be visualized as the central peak of the Cross-Correlogram of spike trains from two MUs. It is widely believed that a common pre-synaptic input to motoneurons from the cortical tract generates the concurrence. A number of synchronization indices have been proposed in order to evaluate the quantity of the common input, however, these indices are dependent on the firing rates of the MUs. To resolve this issue, we introduce a new synchronization index beta using a joint peri-stimulus time histograms (JPSTH). In this paper, we discuss the dependence of synchronization indices on firing rates using a spike model, and the application of JPSTH and the index beta to experimental data for the quantitative analysis of MU synchronization. We confirm that the novel index beta represents the synchronization state independently from firing rates, and that it also accurately traces event-related temporal modulation of synchronization. In conclusion, we consider the index beta to be a valuable index for the analysis of MU synchronization.

Action Potentials↗