Published papers

Previous simulation and experimental studies have demonstrated that the application of Variational Bayesian Multimodal EncephaloGraphy (VBMEG) to magnetoencephalography (MEG) data can be used to estimate cortical currents with high spatio-temporal resolution, by incorporating functional magnetic resonance imaging (fMRI) activity as a hierarchical prior. However, the use of combined MEG and fMRI is restricted by the high costs involved, a lack of portability and high sensitivity to body-motion artifacts. One possible solution for overcoming these limitations is to use a combination of electroencephalography (EEG) and near-infrared spectroscopy (NIRS). This study therefore aimed to extend the possible applications of VBMEG to include EEG data with NIRS activity as a hierarchical prior. Using computer simulations and real experimental data, we evaluated the performance of VBMEG applied to EEG data under different conditions, including different numbers of EEG sensors and different prior information. The results suggest that VBMEG with NIRS prior performs well, even with as few as 19 EEG sensors. These findings indicate the potential value of clinically applying VBMEG using a combination of EEG and NIRS. © 2011 Elsevier Inc..

Purpose.To study the adaptation process for standing postural control in patients with hemiparesis after stroke. Methods.The changes of a standing posture developed in nine hemiparetic patients who had never maintained an upright stance alone (aged 4862 years; 619 days after stroke) was evaluated by recording ground reaction forces and surface electromyographic (EMG) from lower limbs. A 60-s standing trial without any instruction about body alignment was repeated five times, and the experience-related changes of centre of pressure (COP) and integrated EMG data were estimated. Results.In the early standing trials, patients balanced themselves by managing the average COP position around the midline of both feet, accompanied by increased muscular activity of the non-paretic leg. COP displacement gradually decreased in the later standing trials (P<0.05). Postural adaptations were achieved by shifting the centre of body sway to the side of the non-paretic foot (P<0.05) while reducing biceps femoris muscular activity (P<0.01) in the non-paretic leg. Conclusions.This study revealed that weight-bearing asymmetry might contribute to improving increased body sway and muscular over-activity of the non-paretic leg. When planning rehabilitative treatment for hemiparetic patients, we should consider that weight-bearing asymmetry may be a result of systematic postural control. © 2011 Informa UK, Ltd.

Background: To more accurately evaluate rehabilitation outcomes in stroke patients, movement irregularities should be quantified. Previous work in stroke patients has revealed a reduction in the trajectory smoothness and segmentation of continuous movements. Clinically, the Stroke Impairment Assessment Set (SIAS) evaluates the clumsiness of arm movements using an ordinal scale based on the examiner's observations. In this study, we focused on three-dimensional curvature of hand trajectory to quantify movement, and aimed to establish a novel measurement that is independent of movement duration. We compared the proposed measurement with the SIAS score and the jerk measure representing temporal smoothness. Methods. Sixteen stroke patients with SIAS upper limb proximal motor function (Knee-Mouth test) scores ranging from 2 (incomplete performance) to 4 (mild clumsiness) were recruited. Nine healthy participant with a SIAS score of 5 (normal) also participated. Participants were asked to grasp a plastic glass and repetitively move it from the lap to the mouth and back at a conformable speed for 30 s, during which the hand movement was measured using OPTOTRAK. The position data was numerically differentiated and the three-dimensional curvature was computed. To compare against a previously proposed measure, the mean squared jerk normalized by its minimum value was computed. Age-matched healthy participants were instructed to move the glass at three different movement speeds. Results: There was an inverse relationship between the curvature of the movement trajectory and the patient's SIAS score. The median of the -log of curvature (MedianLC) correlated well with the SIAS score, upper extremity subsection of Fugl-Meyer Assessment, and the jerk measure in the paretic arm. When the healthy participants moved slowly, the increase in the jerk measure was comparable to the paretic movements with a SIAS score of 2 to 4, while the MedianLC was distinguishable from paretic movements. Conclusions: Measurement based on curvature was able to quantify movement irregularities and matched well with the examiner's observations. The results suggest that the quality of paretic movements is well characterized using spatial smoothness represented by curvature. The smaller computational costs associated with this measurement suggest that this method has potential clinical utility. © 2011 Osu et al; licensee BioMed Central Ltd.

Recently, surface electroencephalogram (EEG)-based brain-machine interfaces (BMI) have been used for people with disabilities. As a BMI signal source, event-related desynchronization of alpha-band EEG (8-13 Hz) during motor imagery (mu ERD), which is interpreted as desynchronized activities of the activated neurons, is commonly used. However, it is often difficult for patients with severe hemiparesis to produce mu ERD of sufficient strength to activate BMI. Therefore, whether it is possible to modulate mu ERD during motor imagery with anodal transcranial direct-current stimulation (tDCS) was assessed in a severe left hemiparetic stroke patient. EEG was recorded over the primary motor cortex (M1), and mu ERD during finger flexion imagery was measured before and after a 5-day course of tDCS applied to M1. The ERD recorded over the affected M1 increased significantly after tDCS intervention. Anodal tDCS may increase motor cortex excitability and potentiate ERD during motor imagery in patients with severe hemiparetic stroke. © 2011 by The Keio Journal of Medicine.

Objective: To examine the short-term effects of a newly developed hemiparetic gait training in which patients walk with a prosthesis applied to the nonparetic leg in the flexed knee position. Design: Pre-post nonrandomized controlled trial. Setting: Rehabilitation center and gait laboratory of a university hospital. Participants: Community-dwelling ambulatory volunteers (N=22) with chronic hemiparesis caused by a unilateral stroke. Intervention: Study subjects participated in a gait training program using either a below-knee prosthesis or a treadmill. Treadmill gait training was performed at a speed approximating the maximum gait velocity for each patient. The 3-week program consisted of a 5-minute gait training session 2 to 3 times a day. Main Outcome Measures: The ground reaction forces, stance time, step length and cadence during walking at a comfortable speed, and maximum gait speed, as well as the Berg Balance Score, were estimated before and after each training program. Results: In comparison with changes after the treadmill gait training, analyses of covariance demonstrated a significant increase of the fore-aft ground reaction forces during the paretic propulsion phase and a significant increase in the relative durations of the paretic and nonparetic single stance involved in a gait cycle after the prosthetic gait training (P<.05). Conclusions: Prosthetic gait training would have different effects on a hemiparetic gait than treadmill gait training. The gait-related task inducing the dominant use of the paretic leg to support the body may be useful as a rehabilitative treatment to improve the kinetic abilities in the paretic stance period. © 2011 American Congress of Rehabilitation Medicine.

Background and objective. Hybrid assistive neuromuscular dynamic stimulation (HANDS) therapy was devised to facilitate the use of the hemiparetic upper extremity in daily life by combining assistive neuromuscular electrical stimulation, referred to as the integrated volitional electrical stimulator (IVES), with a splint. The aim of this study is to assess the effectiveness of HANDS therapy for patients with subacute stroke. Methods. The participants were 24 inpatients receiving rehabilitation for hemiparetic stroke within 60 days of onset. Entry criteria included inability to individuate finger extension. Patients were randomly assigned to 2 groups. The HANDS group (n = 12) used the IVES combined with a wrist splint for 8 hours a day for 3 weeks, and the control group (n = 12) wore a wrist splint alone. All patients received the same daily dose and length of standard poststroke multidisciplinary rehabilitation. Outcome measures were the upper extremity portion of the Fugl-Meyer Assessment (FMA), Action Research Arm Test (ARAT), and Motor Activity Log-14 (MAL). Results. In all, 10 patients in each group completed the interventions. Compared with the control group, the HANDS group showed significantly greater gains in distal (wrist/hand) portion of the FMA (P <.01) and improvement of the ARAT (P <.05). The gains in the MAL did not differ. No adverse effects occurred and the HANDS therapy was well accepted. Conclusion. HANDS therapy in addition to conventional therapy may improve hand function in patients with moderate to severe hand impairment during early rehabilitation. © 2011 American Society of Neurorehabilitation.

Background and objective. Unilateral spatial neglect (USN) can interfere with rehabilitation processes and lead to poor functional outcome. The purpose of this study was to determine whether prism adaptation (PA) therapy improves USN and functional outcomes in stroke patients in the subacute stage. Methods. A multicenter, double-masked, randomized, controlled trial was conducted to evaluate the effects of a 2-week PA therapy on USN assessed with the Behavioral Inattention Test (BIT), the Catherine Bergego Scale (CBS), and activities of daily living (ADL) as evaluated with the Functional Independence Measure (FIM). A total of 38 USN patients with right-brain damage were divided into prism (n = 20) and control (n = 18) groups. Patients were divided into mild and severe USN groups according to BIT behavioral test (mild 55 and severe<55). The prism group performed repetitive pointing with prism glasses that induce rightward optical shift twice daily, 5 days per week, for 2 weeks, whereas the control group performed similar pointing training with neutral glasses. Results. The FIM improved significantly more in the prism group. In mild USN patients, there was significantly greater improvement of BIT and FIM in the prism group. Conclusions. PA therapy can significantly improve ADL in patients with subacute stroke. © 2011 American Society of Neurorehabilitation.

To explore the effectiveness of neurorehabilitative training using an electroencephalogram-based brain-computer interface for hand paralysis following stroke. Design: A case series study. Subjects: Eight outpatients with chronic stroke demonstrating moderate to severe hemiparesis. Methods: Based on analysis of volitionally decreased amplitudes of sensory motor rhythm during motor imagery involving extending the affected fingers, real-time visual feedback was provided. After successful motor imagery, a mechanical orthosis partially extended the fingers. Brain-computer interface interventions were carried out once or twice a week for a period of 4-7 months, and clinical and neurophysiological examinations pre- and post-intervention were compared. Results: New voluntary electromyographic activity was measured in the affected finger extensors in 4 cases who had little or no muscle activity before the training, and the other participants exhibited improvement in finger function. Significantly greater suppression of the sensory motor rhythm over both hemispheres was observed during motor imagery. Transcranial magnetic stimulation showed increased cortical excitability in the damaged hemisphere. Success rates of brain-computer interface training tended to increase as the session progressed in 4 cases. Conclusion: Brain-computer interface training appears to have yielded some improvement in motor function and brain plasticity. Further controlled research is needed to clarify the role of the brain-computer interface system. © 2011 The Authors.

Oscillatory activity of the sensorimotor cortex has been reported to show coherence with muscle activity in the 15- to 35-Hz frequency band (β-band) during weak to moderate intensity of isometric contraction. The present study examined the variance of the magnitude of the corticomuscular coherence across a large number of subjects. We quantified the coherence between EEG over the sensorimotor cortex and rectified electromyogram (EMG) from the tibialis anterior muscle during tonic isometric contraction at 30% of maximal effort in 100 healthy young individuals. We estimated the maximal peak of EEG-EMG coherence (Cohmax) and the ratio of the sum of the autopower spectral density function within the β -band to that of all frequency ranges for both EEG (EEG β -PSD) and EMG (EMG β -PSD) signals. The frequency histogram of Cohmax across all subjects showed a broad bell-shaped continuous distribution (range, 0.048-0.816). When the coherence was thresholded at the estimated significance level of P < 0.05 (0.114), 46 out of 100 subjects showed significant EEG-EMG coherence. Cohmax occurred within the β -band in the majority of subjects who showed significant EEG-EMG coherence (n = 43). Furthermore, Cohmax showed significant positive correlations with both EEG β - PSD (r = 0.575, P < 0.001) and EMG β -PSD (r = 0.606, P < 0.001). These data suggest that even during simple tonic isometric contraction, the strength of oscillatory coupling between the sensorimotor cortex and spinal motoneurons varies among individuals and is a contributory factor determining muscle activation patterns such as the degree of grouped discharge in muscle activity within the β -band for each subject. © 2011 the American Physiological Society.

Objective: Patterned sensory electrical stimulation (PES) has been shown to induce plasticity in spinal reciprocal Ia inhibition of the calf muscles. To study the cortical modulation of spinal plasticity, we examined the effects of giving transcranial direct current stimulation (tDCS) to the motor cortex before PES. Methods: Seven healthy volunteers participated in this study. PES involved stimulating the left common peroneal nerve at the fibular head with a train of 10 pulses at 100. Hz every 1.5. s for 20. min using an intensity equal to the motor threshold of the tibialis anterior. tDCS was applied for 10. min before PES. For anodal stimulation, the electrode was placed over the motor cortex, and the cathodal electrode over the contralateral supraorbital area. For cathodal stimulation, the electrodes were reversed. Reciprocal inhibition was assessed using a soleus H reflex conditioning-test paradigm. Results: PES increased disynaptic reciprocal inhibition from the peroneal nerve to the soleus H reflex. When cathodal tDCS was applied before PES, PES no longer increased reciprocal inhibition. Conclusions: Applying tDCS before PES modulated the effects of PES on spinal reciprocal inhibition in a polarity specific manner. Significance: We suggest that the motor cortex may play a role in spinal plasticity. © 2011 International Federation of Clinical Neurophysiology.

We evaluated the efficacy of a novel electromyogram (EMG)-controlled electrical stimulation system, called the integrated volitional control electrical stimulator (IVES), on the recovery of upper extremity motor functions in patients with chronic hemiparetic stroke. Ten participants in the chronic stage (more than 12 months post-stroke with partial paralysis of their wrist and fingers) received treatment with IVES to the extensor carpi radialis and extensor digitorum communis 6 h/day for 5 days. Before and after the intervention, participants were assessed using upper-extremity Fugl-Meyer motor assessment (FMA), the active range of motion (A-ROM), the nine-hole peg test (NHPT), and surface EMG recordings. The upper extremity FMA showed a statistically significant increase from 50.8 ± 5.8 to 56.8 ± 6.2 after the intervention (P < 0.01). The A-ROM of wrist extension was also significantly improved from 36.0° ± 15.4° to 45.0° ± 15.5° (P < 0.01). The NHPT significantly decreased from 85.3 ± 52.0 to 63.3 ± 29.7 (P = 0.04). EMG measurements demonstrated statistically significant improvements in the coactivation ratios for the wrist flexor and extensor muscles after the intervention. This study suggested that 5 days of IVES treatment yields a noticeable improvement in upper extremity motor functions in patients with chronic hemiparetic stroke. © 2011 by The Keio Journal of Medicine.

Oscillatory activity of the sensorimotor cortex shows coherence with muscle activity within the 15-to 35-Hz frequency band (β-band) during weak to moderate sustained isometric contraction. We aimed to examine the acute changes in this corticomuscular coupling due to muscle fatigue and its effect on the steadiness of the exerted force. We quantified the coherence between the electroencephalogram (EEG) recorded over the sensorimotor cortex and the rectified surface electromyogram (EMG) of the tibialis anterior muscle as well as the coefficient of variance of the dorsiflexion force (ForceCV) and sum of the autopower spectral density function of the force within the β-band (Forceβ -PSD) during 30% of maximal voluntary contraction (MVC) for 60 s before (prefatiguing task) and after (postfatiguing task) muscle fatigue induced by sustained isometric contraction at 50% of MVC until exhaustion in seven healthy male subjects. The magnitude of the EEG-EMG coherence increased in the postfatiguing task in six of seven subjects. The maximal peak of EEG-EMG coherence stayed within the β-band in both pre-and postfatiguing tasks. Interestingly, two subjects, who had no significant EEG-EMG coherence in the prefatiguing task, showed significant coherence in the postfatiguing task. Additionally, ForceCV and Force β-PSD significantly increased after muscle fatigue. These data suggest that when muscle fatigue develops, the central nervous system enhances oscillatory muscular activity in the β-band stronger coupled with the sensorimotor cortex activity accomplishing the sustained isometric contraction at lower performance levels. © 2011 the American Physiological Society.

Background. The mu event-related desynchronization (ERD) is supposed to reflect motor preparation and appear during motor imagery. The aim of this study is to examine the modulation of ERD with transcranial direct current stimulation (tDCS). Methods. Six healthy subjects were asked to imagine their right hand grasping something after receiving a visual cue. Electroencephalograms (EEGs) were recorded near the left M1. ERD of the mu rhythm (mu ERD) by right hand motor imagery was measured. tDCS (10 min, 1 mA) was used to modulate the cortical excitability of M1. Anodal, cathodal, and sham tDCS were tested in each subject with a randomized sequence on different days. Each condition was separated from the preceding one by more than 1 week in the same subject. Before and after tDCS, mu ERD was assessed. The motor thresholds (MT) of the left M1 were also measured with transcranial magnetic stimulation. Results. Mu ERD significantly increased after anodal stimulation, whereas it significantly decreased after cathodal stimulation. There was a significant correlation between mu ERD and MT. Conclusions. Opposing effects on mu ERD based on the orientation of the stimulation suggest that mu ERD is affected by cortical excitability. © 2010 Matsumoto et al; licensee BioMed Central Ltd.

To assess the similarity between cortical activities observed during actual and imaginary motor tasks, we evaluated electroencephalography-electromyography (EEG-EMG) coherence during motor task execution (ME) and the same task-related EEG power increase (TRPI) during kinesthetic motor imagery (MI). EEGs recorded at the vertex and EMGs recorded at the right tibialis anterior muscle (TA) were analyzed in 13 healthy subjects. Subjects were requested to perform: (1) isometric TA contraction, (2) imagery of the same movement without overt motor behavior, and (3) rest without MI. The results show significant EEG-EMG coherence during ME, as well as TRPI during both ME and MI tasks within a similar 14-30 Hz band. The magnitude of EEG-EMG coherence and TRPI varied among the subjects. Intersubject analysis revealed a significant correlation between EEG-EMG coherence and TRPI. These results support the hypothesis that ME and MI tasks involve overlapping neural networks in the perirolandic cortical areas. © 2010 by Polish Neuroscience Society - PTBUN.

Background: For severely paralyzed people, a brain-computer interface (BCI) provides a way of re-establishing communication. Although subjects with muscular dystrophy (MD) appear to be potential BCI users, the actual long-term effects of BCI use on brain activities in MD subjects have yet to be clarified. To investigate these effects, we followed BCI use by a chronic tetraplegic subject with MD over 5 months. The topographic changes in an electroencephalogram (EEG) after long-term use of the virtual reality (VR)-based BCI were also assessed. Our originally developed BCI system was used to classify an EEG recorded over the sensorimotor cortex in real time and estimate the user's motor intention (MI) in 3 different limb movements: feet, left hand, and right hand. An avatar in the internet-based VR was controlled in accordance with the results of the EEG classification by the BCI. The subject was trained to control his avatar via the BCI by strolling in the VR for 1 hour a day and then continued the same training twice a month at his home.Results: After the training, the error rate of the EEG classification decreased from 40% to 28%. The subject successfully walked around in the VR using only his MI and chatted with other users through a voice-chat function embedded in the internet-based VR. With this improvement in BCI control, event-related desynchronization (ERD) following MI was significantly enhanced (p < 0.01) for feet MI (from -29% to -55%), left-hand MI (from -23% to -42%), and right-hand MI (from -22% to -51%).Conclusions: These results show that our subject with severe MD was able to learn to control his EEG signal and communicate with other users through use of VR navigation and suggest that an internet-based VR has the potential to provide paralyzed people with the opportunity for easy communication. © 2010 Hashimoto et al; licensee BioMed Central Ltd.

We previously reported the beneficial effect of administering an anti-mouse IL-6 receptor antibody (MR16-1) immediately after spinal cord injury (SCI). The purpose of our present study was to clarify the mechanism underlying how MR16-1 improves motor function after SCI. Quantitative analyses of inflammatory cells using flow cytometry, and immunohistochemistry with bone marrow-chimeric mice generated by transplanting genetically marked purified hematopoietic stem cells, revealed that MR16-1 dramatically switched the central player in the post-traumatic inflammation, from hematogenous macrophages to resident microglia. This change was accompanied by alterations in the expression of relevant cytokines within the injured spinal cord; the expression of recruiting chemokines including CCL2, CCL5, and CXCL10 was decreased, while that of Granulocyte/Macrophage-Colony Stimulating Factor (GM-CSF), a known mitogen for microglia, was increased. We also showed that the resident microglia expressed higher levels of phagocytic markers than the hematogenous macrophages. Consistent with these findings, we observed significantly decreased tissue damage and reduced levels of myelin debris and Nogo-A, the axonal growth inhibitor, by MR16-1 treatment. Moreover, we observed increased axonal regeneration and/or sprouting in the MR16-1-treated mice. Our findings indicate that the functional improvement elicited by MR16-1 involves microglial functions, and provide new insights into the role of IL-6 signaling in the pathology of SCI. © 2010 Elsevier Inc.