Teiji Kawano

Near-infrared Spectroscopy–mediated Neurofeedback Enhances Efficacy of Motor Imagery–based Training in Poststroke Victims A Pilot Study

Background and Purpose— Despite the findings that motor imagery and execution are supposed to share common neural networks, previous studies using imagery-based rehabilitation have revealed inconsistent results. In the present study, we investigated whether feedback of cortical activities (neurofeedback) using near-infrared spectroscopy could enhance the efficacy of imagery-based rehabilitation in stroke patients. Methods— Twenty hemiplegic patients with subcortical stroke received 6 sessions of mental practice with motor imagery of the distal upper limb in addition to standard rehabilitation. Subjects were randomly allocated to REAL and SHAM groups. In the REAL group, cortical hemoglobin signals detected by near-infrared spectroscopy were fed back during imagery. In the SHAM group, irrelevant randomized signals were fed back. Upper limb function was assessed using the finger and arm subscales of the Fugl-Meyer assessment and the Action Research Arm Test. Results— The hand/finger subscale of the Fugl-Meyer assessment showed greater functional gain in the REAL group, with a significant interaction between time and group (F2,36=15.5; P<0.001). A significant effect of neurofeedback was revealed even in severely impaired subjects. Imagery-related cortical activation in the premotor area was significantly greater in the REAL group than in the SHAM group (T58=2.4; P<0.05). Conclusions— Our results suggest that near-infrared spectroscopy–mediated neurofeedback may enhance the efficacy of mental practice with motor imagery and augment motor recovery in poststroke patients with severe hemiparesis.

Neurofeedback Using Real-Time Near-Infrared Spectroscopy Enhances Motor Imagery Related Cortical Activation

Accumulating evidence indicates that motor imagery and motor execution share common neural networks. Accordingly, mental practices in the form of motor imagery have been implemented in rehabilitation regimes of stroke patients with favorable results. Because direct monitoring of motor imagery is difficult, feedback of cortical activities related to motor imagery (neurofeedback) could help to enhance efficacy of mental practice with motor imagery. To determine the feasibility and efficacy of a real-time neurofeedback system mediated by near-infrared spectroscopy (NIRS), two separate experiments were performed. Experiment 1 was used in five subjects to evaluate whether real-time cortical oxygenated hemoglobin signal feedback during a motor execution task correlated with reference hemoglobin signals computed off-line. Results demonstrated that the NIRS-mediated neurofeedback system reliably detected oxygenated hemoglobin signal changes in real-time. In Experiment 2, 21 subjects performed motor imagery of finger movements with feedback from relevant cortical signals and irrelevant sham signals. Real neurofeedback induced significantly greater activation of the contralateral premotor cortex and greater self-assessment scores for kinesthetic motor imagery compared with sham feedback. These findings suggested the feasibility and potential effectiveness of a NIRS-mediated real-time neurofeedback system on performance of kinesthetic motor imagery. However, these results warrant further clinical trials to determine whether this system could enhance the effects of mental practice in stroke patients.

Cortical changes underlying balance recovery in patients with hemiplegic stroke.

Balance problems are a major sequelae of stroke and are implicated in poor recovery of activities of daily living. In a cross-sectional study, using 50-channel event-related functional near-infrared spectroscopy we previously reported a significant correlation between individual balance ability after stroke and postural perturbation-related cortical activation in the supplementary motor area (SMA) and the prefrontal cortex. However, the neural mechanisms underlying balance recovery after stroke remain unclear. Herein, we examined the cortical involvement in balance recovery after stroke by determining longitudinal regional cortical activation changes in patients with hemiplegic stroke. Twenty patients with subcortical stroke admitted to our hospital for post-acute inpatient rehabilitation participated in this study. Before and after intensive inpatient physical and occupational therapy rehabilitation, we evaluated cortical activation associated with external postural perturbations induced by combined brisk forward and backward movement on a platform. Postural perturbation-related cortical activation in the SMA of the affected and unaffected hemispheres was significantly increased after intensive rehabilitation. The increment of the postural-perturbation-related oxygenated hemoglobin signals in the SMA of the unaffected hemisphere was significantly correlated with the gain in balance function measured by the Berg Balance Scale. These findings support the conclusion that the SMA plays an important role in postural balance control, and suggest that the SMA is a crucial area for balance recovery after hemiplegic stroke.

Cortical control of postural balance in patients with hemiplegic stroke.

Despite its remarkable effect on the activities of daily living, the precise mechanism underlying balance control after stroke remains to be elucidated. In this study, we investigated the cortical activation induced by postural perturbation in 20 patients with stroke using a 50-channel event-related functional near-infrared spectroscopy. A combination of brisk forward and backward movements of a platform without any prior cue was used as an external postural perturbation. Multi-participant analysis of oxygenated hemoglobin signals showed postural perturbation-related cortical activation in the prefrontal cortical areas in both hemispheres as well as the premotor and parietal association cortical areas in the unaffected hemisphere. Regression analysis using the individual Berg Balance Scale as the regressor showed a significant positive correlation between balance ability and the postural perturbation-related changes in oxygenated hemoglobin signals in the supplementary motor areas and prefrontal cortical areas in both hemispheres. Consistent with the previous findings in healthy participants, these findings suggest that the broad cortical network, including the prefrontal, premotor, supplementary motor, and parietal cortical areas in both hemispheres, was essential for balance control even in poststroke patients.

Plasma D-dimer levels and ischaemic lesions in multiple vascular regions can predict occult cancer in patients with cryptogenic stroke.

Cancer patients with cryptogenic stroke often have high plasma D‐dimer levels and lesions in multiple vascular regions. Hence, if patients with cryptogenic stroke display such characteristics, occult cancer could be predicted. This study aimed to investigate the clinical characteristics of cryptogenic stroke as the first manifestation of occult cancer and to determine whether plasma D‐dimer levels and lesions in multiple vascular regions can predict occult cancer in patients with cryptogenic stroke.

Large-Scale Phase Synchrony Reflects Clinical Status After Stroke: An EEG Study:

Background and Purpose. Stroke-induced focal brain lesions often exert remote effects via residual neural network activity. Electroencephalographic (EEG) techniques can assess neural network modifications after brain damage. Recently, EEG phase synchrony analyses have shown associations between the level of large-scale phase synchrony of brain activity and clinical symptoms; however, few reports have assessed such associations in stroke patients. Objective. The aim of this study was to investigate the clinical relevance of hemispheric phase synchrony in stroke patients by calculating its correlation with clinical status. Methods. This cross-sectional study included 19 patients with post-acute ischemic stroke admitted for inpatient rehabilitation. Interhemispheric phase synchrony indices (IH-PSIs) were computed in 2 frequency bands (alpha [α], and beta [β]), and associations between indices and scores of the Functional Independence Measure (FIM), the National Institutes of Health Stroke Scale (NIHSS), and the Fugl−Meyer Motor Assessment (FMA) were analyzed. For further assessments of IH-PSIs, ipsilesional intrahemispheric PSIs (IntraH-PSIs) as well as IH- and IntraH-phase lag indices (PLIs) were also evaluated. Results. IH-PSIs correlated significantly with FIM scores and NIHSS scores. In contrast, IH-PSIs did not correlate with FMA scores. IntraH-PSIs correlate with FIM scores after removal of the outlier. The results of analysis with PLIs were consistent with IH-PSIs. Conclusions. The PSIs correlated with performance on the activities of daily living scale but not with scores on a pure motor impairment scale. These results suggest that large-scale phase synchrony represented by IH-PSIs provides a novel surrogate marker for clinical status after stroke.

The Repertoire of Brain Synchronized States Accounts for Stroke Recovery

We demonstrate the first experimental evidence that fluctuations in electroencephalographic (EEG) resting-state connectivity are associated with recovery from stroke. We found that fluctuations in instantaneous brain states, quantified as the variance in EEG phase synchronized states, were correlated with motor-related subscores in the Functional Independence Measure, which estimates the recovery of activities of daily living (ADL) in stroke patients. The results suggest that the dynamic repertoire of spontaneous large-scale phase synchronization networks constrains functional networking and accounts for the ADL recovery.

Neurofeedback-induced facilitation of the supplementary motor area affects postural stability

Abstract. Near-infrared spectroscopy-mediated neurofeedback (NIRS-NFB) is a promising therapeutic intervention for patients with neurological diseases. Studies have shown that NIRS-NFB can facilitate task-related cortical activation and induce task-specific behavioral changes. These findings indicate that the effect of neuromodulation depends on local cortical function. However, when the target cortical region has multiple functions, our understanding of the effects is less clear. This is true in the supplementary motor area (SMA), which is involved both in postural control and upper-limb movement. To address this issue, we investigated the facilitatory effect of NIRS SMA neurofeedback on cortical activity and behavior, without any specific task. Twenty healthy individuals participated in real and sham neurofeedback. Balance and hand dexterity were assessed before and after each NIRS-NFB session. We found a significant interaction between assessment periods (pre/post) and condition (real/sham) with respect to balance as assessed by the center of the pressure path length but not for hand dexterity as assessed by the 9-hole peg test. SMA activity only increased during real neurofeedback. Our findings indicate that NIRS-NFB itself has the potential to modulate focal cortical activation, and we suggest that it be considered a therapy to facilitate the SMA for patients with postural impairment.

Correlation between motor impairment and increased contralateral cerebellar activity during paralytic hand movement after stroke

Somatosensory afferent stimulation modulates neuronal activity in the central motor system, which can benefit human motor functions. Prompted by a previous finding that brief pre-movement sensory manipulation using transcutaneous electrical nerve stimulation (TENS) can promote efficient control of a hand motor skill and improve the motor performance, we examined whether brief TENS facilitates initial learning of the motor skill by promoting its efficient control. Fourteen healthy participants repeatedly practiced a novel motor task, involving rotation of two balls as many times as possible in 30 s with their fingers (maximum rotation). This was immediately followed by constant rotation task where they rotated the balls at 1 Hz for 30 s. In each participant, this pair was repeated with inter-trial-interval of 1 min until total number of rotation reached 1000 times. Seven participants received 1-min TENS to relaxed thenar muscles before each trial of maximum rotation task (TENS group), while the other 7 participants received no particular stimulation (Control group). We evaluated the number of rotations in each trial measured by a sensor attached to the thumb. We also recorded electromyographic (EMG) activity from a forearm muscle, and analyzed integrated EMG during the performance of constant rotation task as an index for efficient control. We found that, in both groups, the number of rotations gradually increased in the maximum rotation task as the practice was repeated. But, as compared to the Control group, the performance was significantly improved in the TENS group, where significant reduction of integrated EMG proceeded during the performance of constant rotation task. These results suggest that intervention using pre-movement brief (1 min) sensory manipulation can facilitate initial learning of a complex motor skill by promoting its efficient motor control.

P35-8 Correlation between motor impairment and increased contralateral cerebellar activity during paralytic hand movement after stroke

hemodynamics measured by acetazolamide challenged CT perfusion (CTP) imaging in patients with moyamoya syndrome associated with atherosclerotic occlusion of the middle cerebral arteries (MCA). Methods: Six patients with moyamoya syndrome associated with unilateral (n = 3) or bilateral (n = 3) atherosclerotic occlusion of the proximal MCA (mean age, 63 years) underwent cerebral angiography and CTP imaging. The control group consisted of 4 subjects (mean age, 60.3 years) without hemodynamically significant cerebral artery stenosis. CT examination was performed using a multidetector helical CT scanner (Light Speed 16, GE Healthcare, USA). Quantitative values of regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), and mean transit time (rMTT) were measured in the MCA, anterior (ACA), and posterior cerebral artery (PCA) territories. The Cerebral vascular reserve (CVR) capacity were measured using acetazolamide. Results: The baseline rCBF in the affected MCA of the moyamoya syndrome was significantly reduced than in the control group (P= 0.05). However, All rCBF, rCBV, and rCBV parameters were not significantly influenced by administration of acetazolamide. The CVR capacity was not significantly changed among the affected MCA, ACA, and PCA territories. Conclusions: These findings suggest that the hemodynamics in moyamoya syndrome associated with atherosclerotic occlusion of the MCA were relatively preserved by abundant collateral circulation through the basal moyamoya vessels.