Yoshihiro Muraoka - Academia.edu (original) (raw)

Papers by Yoshihiro Muraoka

Journal of Physical Therapy Science, 2017

The soleus H-reflex is depressed at stimulation rates greater than 0.1 Hz. This reflex depression... more The soleus H-reflex is depressed at stimulation rates greater than 0.1 Hz. This reflex depression is referred to as postactivation depression. Postactivation depression reflects the reduced efficacy of the Iamotoneurons synapses when they are evaluated after a previous activation. The aim of this study was to determine whether the recovery of motor functions in the lower extremities affects the PAD of the soleus H-reflex in patients with subacute stroke undergoing rehabilitation. [Subjects and Methods] Eight patients with subacute stroke patients were recruited. Postactivation depression, Fugl-Meyer score (lower-limb portion), walking velocity, the Modified Ashworth Scale, and center of pressure sway during standing were measured within three days of admission to rehabilitation and 50 days later. [Results] After rehabilitation, Fugl-Meyer scores, center of pressure path length, and walking velocity were significantly improved, and postactivation depression had significantly increased. There was a significant positive correlation between the rates of change of postactivation depression and center of pressure path length. [Conclusion] The results demonstrated that postactivation depression is partially normalized after rehabilitation in patients with subacute stroke, and suggested that the recovery in lower extremity function after stroke particularly standing stability is affected by spinal synaptic plasticity.

The Japanese Journal of Rehabilitation Medicine, 2002

The Japanese Journal of Rehabilitation Medicine, 2005

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2013

An electromyogram (EMG)-driven neuromuscular stimulator for upper limb functional recovery (Murao... more An electromyogram (EMG)-driven neuromuscular stimulator for upper limb functional recovery (Muraoka et al., 1998) can stimulate target muscles in proportion to the amount of voluntary EMG of the identical target muscles. Furthermore, it can facilitate the contraction of paralyzed muscles by electrical stimulation at subthreshold intensity level. Although it has been suggested that to use the stimulator for as long a time as possible might be needed for more effective treatment, the utilization time was limited by the size of the stimulator, which involved a laptop personal computer. To use in daily life, the device was improved to be a smaller size of 95×65×40 mm (including batteries) which was equivalent to a mobile phone (in 2002). The stimulator was called the Integrated Volitional-control Electrical Stimulator (IVES). IVES has already been manufactured and its use has spread in Japan since 2008. Nowadays, therapy using IVES is an effective therapy to improve the motor function o...

The Tokai journal of experimental and clinical medicine, Jan 20, 2013

Changes in cortical excitability during motor imagery were investigated in order to reveal the ef... more Changes in cortical excitability during motor imagery were investigated in order to reveal the effect of hand dominance. During motor imagery, motor evoked potentials (MEPs) were recorded from the first dorsal interosseous (FDI) muscle of the dominant hand using transcranial magnetic stimulation (TMS). Twelve healthy right-handed subjects participated. Three motor imagery tasks (MITs) were provided; dominant hand grasping, non-dominant hand grasping, and ankle dorsiflexion ipsilateral to the dominant hand. MEPs were also recorded from the FDI muscle of the non-dominant hand during the same tasks. MEPs increased significantly in the dominant hand during MIT, just before MIT of the dominant hand, and prior to ankle dorsiflexion ipsilateral to the dominant hand. MEPs obtained from the FDI muscle of the dominant hand during MITs were greater than that obtained from the FDI muscle of the non-dominant hand. However, this difference was not significant. The left primary motor cortex (M1) w...

PloS one, 2012

While previous studies have assessed changes in corticospinal excitability following voluntary co... more While previous studies have assessed changes in corticospinal excitability following voluntary contraction coupled with electrical stimulation (ES), we sought to examine, for the first time in the field, real-time changes in corticospinal excitability. We monitored motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation and recorded the MEPs using a mechanomyogram, which is less susceptible to electrical artifacts. We assessed the MEPs at each level of muscle contraction of wrist flexion (0%, 5%, or 20% of maximum voluntary contraction) during voluntary wrist flexion (flexor carpi radialis (FCR) voluntary contraction), either with or without simultaneous low-frequency (10 Hz) ES of the median nerve that innervates the FCR. The stimulus intensity corresponded to 1.2 × perception threshold. In the FCR, voluntary contraction with median nerve stimulation significantly increased corticospinal excitability compared with FCR voluntary contraction without median nerve ...

Electromyography and clinical neurophysiology, 2007

Hybrid exercise (HE) was designed to use the force generated by an electrically stimulated antago... more Hybrid exercise (HE) was designed to use the force generated by an electrically stimulated antagonist to provide resistance to a volitionally contracting agonist. The purpose of this study was to measure and compare the soleus H-reflex before and after HE or conventional resistance exercise (CRE). The experiments were carried out in 18 healthy subjects (5 men and 13 women; 19-30 yr), who were divided into 2 groups of 9 for each protocol (HE or CRE). The exercise sessions lasted for 15 consecutive minutes. The soleus Hmax/Mmax was measured before and after the HE or the CRE. In the HE group, although there was no significant difference, the soleus Hmax/Mmax after the exercise increased compared with before the exercise (54.7 +/- 10.2% to 59.0 +/- 14.5%). On the other hand, the soleus Hmax/Mmax decreased in the CRE group (61.8 +/- 14.9% to 55.7 +/- 16.1%). In the rate of change of the soleus Hmax/Mmax, the result for the HE group was significantly higher than in the CRE group (108.0 +...

Electromyography and clinical neurophysiology

The soleus H-reflex during passive hip movement was measured to clarify the modulation of excitab... more The soleus H-reflex during passive hip movement was measured to clarify the modulation of excitability of the soleus monosynaptic reflex during locomotion-like movement in spastic stroke patients. The experiment was performed in five patients with spastic hemiparesis. The hip joint was moved passively ranging from 0 to 40 degrees. The knee joint was fixed at full extension and the ankle joint was fixed at the mid-position. During the movement, the soleus M-wave and soleus H-reflex were measured. Flexion caused a decrease in the soleus H-reflex, whereas extension caused an increase symmetrically for both the static and dynamic conditions. In addition, the lowest value was observed at the end of the flexion phase during fast movement. These findings indicate that the phase-related modulation of soleus H-reflex during hip movement is partially disordered in stroke patients.

The International journal of neuroscience, 2006

The aim of the study was to investigate the modulation of the soleus H-reflex during static and d... more 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.

Electromyography and clinical neurophysiology, 2004

The study aims to investigate the changes of the H-reflex in soleus (Sol-H-reflex) during hip and... more The study aims to investigate the changes of the H-reflex in soleus (Sol-H-reflex) during hip and knee joint movements in stroke patients. The experiments were carried out on five stroke patients with spastic hemiplegia (2 males and 3 females, 48 to 71 years old). Sol-H-reflexes were measured 200 times for each joint movement speed Stimulus was given at random intervals (4 to 5 seconds) during the joint movement. Two movement speeds were used to investigate the effects of movement speed. For both fast and slow movements, the amplitude of the Sol-H-reflex decreased in the middle flexion phase. In contrast, the amplitude of the Sol-H-reflex increased in the middle extension phase. For the fast movement, the Sol-H-reflex was smaller in only a small angle range during the flexion and extension phase in comparison to the slow movement. The Sol-H-reflex during the flexion phase was significantly smaller than during the extension phase at almost all angles for both speeds. The Sol-H-reflex...

International Journal of Neuroscience, 2005

To elucidate whether hip and knee joint movement modulate soleus H-reflex, the authors measured t... more 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. Eight healthy subjects participated. The knee and hip joints were passively flexed and extended ranging from 0 degrees to 120 degrees simultaneously. In the flexion phase, H-reflex decreased. It decreased more during fast movement. In the extension phase, H-reflex increased markedly. 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.

Neuroscience Research, 2010

Neurorehabilitation and Neural Repair, 2008

Background and objective . We devised a therapeutic approach to facilitate the use of the hemipar... more Background and objective . We devised a therapeutic approach to facilitate the use of the hemiparetic upper extremity (UE) in daily life by combining integrated volitional control electrical stimulation with a wrist splint, called hybrid assistive neuromuscular dynamic stimulation (HANDS). Methods. Twenty patients with chronic hemiparetic stroke (median 17.5 months) had moderate to severe UE weakness. Before and immediately after completing 3 weeks of training in 40-minute sessions, 5 days per week over 3 weeks and wearing the system for 8 hours each day, clinical measures of motor impairment, spasticity, and UE functional scores, as well as neurophysiological measures including electromyography activity, reciprocal inhibition, and intracortical inhibition were assessed. A follow-up clinical assessment was performed 3 months later. Results. UE motor function, spasticity, and functional scores improved after the intervention. Neurophysiologically, the intervention induced restoration...

Neuromodulation: Technology at the Neural Interface, 2012

Objectives: To develop effective electrical stimulation treatment to reduce spasticity, we examin... more Objectives: To develop effective electrical stimulation treatment to reduce spasticity, we examined the optimal stimulus point of the common peroneal nerve. Materials and Methods: The locations of selective stimulus points for the deep peroneal nerve or superficial peroneal nerve fiber were examined in 25 healthy subjects in both legs (50 legs) using the ratio of the tibialis anterior (TA) to the peroneus longus (PL) M-wave amplitude (TA/PL ratio). In addition, we measured reciprocal Ia inhibition in ten healthy subjects. The amount of inhibition was determined from short-latency suppression of the soleus (Sol) H-reflex by conditioning stimuli to the deep or superficial peroneal nerve. The paired t-test was used for statistical analysis. Results: The mean TA/PL ratio during deep peroneal nerve stimulation was significantly different from superficial peroneal nerve stimulation (p < 0.001). The mean stimulus point for the deep peroneal nerve was located 7 Ϯ 5 mm distal and 3 Ϯ 6 mm anterior from the distal edges of the head of fibula and was markedly different from the stimulus point for the superficial peroneal nerve (20 Ϯ 7 mm distal and 12 Ϯ 8 mm posterior). During deep peroneal nerve stimulation, the mean conditioned H-reflex was depressed to 83.8 Ϯ 10.7% of the unconditioned value of the H-reflex. In contrast, during superficial peroneal nerve stimulation, the mean conditioned H-reflex increased to 105.3 Ϯ 5.2%. These values were significantly different (p < 0.001). Conclusions: In the present study, we revealed a stimulus area of the deep peroneal nerve. Also, we observed the inhibitory effects of stimulation upon the deep peroneal nerve at individual stimulus point. Our results appear to indicate that localized stimulation of the deep peroneal nerve is more useful for the reduction of ankle spasticity.

Medical & Biological Engineering & Computing, 2004

A new method of stimulation of the lower extremities was devised that automatically adjusts the s... more A new method of stimulation of the lower extremities was devised that automatically adjusts the stimulation conditions at any angle of the knee joint. An M-wave is considered to indicate the stimulation conditions, because it is the waveform that results from direct stimulation to the axon of the alpha motor neuron. The present device adjusted the stimulation intensity, using multi-regression analysis to evoke an M-wave of preset amplitude. Participants included five people without any neuromuscular impairment. The subjects sat on a chair during the test. The hip joint was fixed at a flexion angle of 90 °, and the ankle joint was fixed at the midposition. During passive knee joint movement ranging from 0 ° to 135 °, M-waves were measured. Electrodes were attached at the popliteal fossa and the patella to stimulate the tibial nerve. Ag-AgCI electrodes were put on the belly of the right soleus muscle for the M-wave measurement. The device was set to give M-waves close to the preset value, lO%Mmax. According to previous research, the allowable limit of M-wave amplitude deviations was reported to be about 5%Mmax. The M-wave amplitudes evoked by the device were in the allowable range (9.24-2.5%Mmax). The device enabled control of the M-wave amplitude over the entire range of motion of the joint. Using this device, it was possible to examine the excitability of the alpha motor neuron pool more precisely.