上原 信太郎

Introduction Qualitative information in the form of written reflection reports is vital for evaluating students’ progress in education. As a pilot study, we used text mining, which analyzes qualitative information with quantitative features, to investigate how rehabilitation students’ goals change during their first year at university. Methods We recruited 109 first-year students (66 physical therapy and 43 occupational therapy students) enrolled in a university rehabilitation course. These students completed an open-ended questionnaire about their learning goals at the time of admission and at 6 and 12 months after admission to the university. Text mining was used to objectively interpret the descriptive text data from all three-time points to extract frequently occurring nouns at once. Then, hierarchical cluster analysis was performed to generate clusters. The number of students who mentioned at least one noun in each cluster was counted and the percentages of students in each cluster were compared for the three periods using Cochran’s Q test. Results The 31 nouns that appeared 10 or more times in the 427 sentences were classified into three clusters: “Socializing,” “Practical Training,” and “Classroom Learning.” The percentage of students in all three clusters showed significant differences across the time periods (p < 0.001 for “Socializing”; p < 0.01 for “Practical Training” and “Classroom Learning”). Conclusion These findings suggest that the students’ learning goals changed during their first year of education. This objective analytical method will enable researchers to examine transitional trends in students’ reflections and capture their psychological changes, making it a useful tool in educational research.

Arm reaching is often impaired in individuals with stroke. Nonetheless, how aiming directions influence reaching performance and how such differences change with motor recovery over time remain unclear. Here, we elucidated kinematic parameters of reaching toward various directions in people with post-stroke hemiparesis in the sub-acute phase. A total of 13 and 15 participants with mild and moderate-to-severe hemiparesis, respectively, performed horizontal reaching in eight directions with their affected and unaffected sides using an exoskeleton robotic device at admission and discharge. The movement time, path length, and number of velocity peaks were computed for the mild group (participants able to reach toward all eight directions). Additionally, the total amount of displacement (i.e., movement quantity) toward two simplified directions (mediolateral or anteroposterior) was evaluated for the moderate-to-severe group (participants who showed difficulty in completing the reaching task). Motor recovery was evaluated using the Fugl-Meyer Assessment.The mild group exhibited decreases in movement parameters when reaching in the anteroposterior direction, irrespective of the side of the arm or motor recovery achieved. The moderate-to-severe group exhibited less movement toward the anteroposterior direction than toward the mediolateral direction at admission; however, this direction-dependent bias in movement quantity decreased, with the movement expanding toward the anteroposterior direction with motor recovery at discharge. These results suggest that direction-dependent differences in the quality and quantity of reaching performance exist in people after stroke, regardless of the presence or severity of hemiparesis. This highlights the need to consider the task work area when designing rehabilitative training.

<jats:sec><jats:title>Introduction</jats:title><jats:p>Contact electrical currents in humans stimulate peripheral nerves at frequencies of &amp;lt;100 kHz, producing sensations such as tingling. At frequencies above 100 kHz, heating becomes dominant, resulting in a sensation of warmth. When the current amplitude exceeds the threshold, the sensation results in discomfort or pain. In international guidelines and standards for human protection from electromagnetic fields, the limit for the contact current amplitude has been prescribed. Although the types of sensations produced by contact current at low frequencies, i.e., approximately 50–60 Hz, and the corresponding perception thresholds have been investigated, there is a lack of knowledge about those in the intermediate-frequency band—particularly from 100 kHz to 10 MHz.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>In this study, we investigated the current-perception threshold and types of sensations for 88 healthy adults (range: 20–79 years old) with a fingertip exposed to contact currents at 100 kHz, 300 kHz, 1 MHz, 3 MHz, and 10 MHz.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The current perception thresholds at frequencies ranging from 300 kHz to 10 MHz were 20–30% higher than those at 100 kHz (<jats:italic>p</jats:italic> &amp;lt; 0.001). In addition, a statistical analysis revealed that the perception thresholds were correlated with the age or finger circumference: older participants and those with larger finger circumferences exhibited higher thresholds. At frequencies of ≥300 kHz, the contact current mainly produced a warmth sensation, which differed from the tingling/pricking sensation produced by the current at 100 kHz.</jats:p></jats:sec><jats:sec><jats:title>Discussion</jats:title><jats:p>These results indicate that there exists a transition of the produced sensations and their perception threshold between 100 kHz and 300 kHz. The findings of this study are useful for revising the international guidelines and standards for contact currents at intermediate frequencies.</jats:p></jats:sec><jats:sec><jats:title>Clinical trial registration</jats:title><jats:p><jats:ext-link>https://center6.umin.ac.jp/cgi-open-bin/icdr_e/ctr_view.cgi?recptno=R000045660</jats:ext-link>, identifier UMIN 000045213.</jats:p></jats:sec>

<p>The mechanisms underlying gravicentric (orientations of object or body relative to ‘gravity’) and egocentric estimates (object orientation relative to the ‘body’) have each been examined, but little is known about the association between their estimates, especially when the head and body is near upright. To tackle this question, we conducted two psychophysical experiments. In Experiment 1, participants were asked to estimate the directions of a visual line (subjective visual vertical; SVV) and of their own body relative to gravity (subjective body tilt; SBT), and the direction of a visual line relative to the body longitudinal axis (subjective visual body axis; SVBA) during a small-range whole-body roll tilt. We evaluated correlations between performances on these tasks as covariates of actual body tilt angles. Our results showed a significant correlation of performance (estimation errors) on the SVBA task with performance on the SBT task but not on the SVV task at a group level, after adjusting for the actual body tilt angles. These results suggest an association between estimates for the SVBA and SBT tasks. To confirm this relationship, in Experiment 2, we assessed whether manipulating the subjective direction of the body axis by providing visual feedback in the SVBA task subsequently affected performance in the SBT task. We found that feedback in the SVBA task significantly shifted the SBT angles, even when the actual body tilt angles were identical. The observed association between the SVBA and SBT performances supports at least a partially shared mechanism underlying body-tilt and egocentric estimates.</p>

The lateral prefrontal cortex (PFC) plays a variety of crucial roles in higher-order cognitive functions. Previous works have attempted to modulate lateral PFC function by applying non-invasive transcranial direct current stimulation (tDCS) and demonstrated positive effects on performance of tasks involving cognitive processes. The neurophysiological underpinning of the stimulation effects, however, remain poorly understood. Here, we explored the neurophysiological after-effects of tDCS over the lateral PFC by assessing changes in the magnitude of interhemispheric inhibition from the lateral PFC to the contralateral primary motor cortex (PFC-M1 IHI). Using a dual-site transcranial magnetic stimulation paradigm, we assessed PFC-M1 IHI before and after the application of tDCS over the right lateral PFC. We conducted a double-blinded, crossover, and counterbalanced design where 15 healthy volunteers participated in three sessions during which they received either anodal, cathodal, and sham tDCS. In order to determine whether PFC-M1 IHI could be modulated at all, we completed the same assessment on a separate group of 15 participants as they performed visuo-motor reaction tasks that likely engage the lateral PFC. The results showed that tDCS over the right lateral PFC did not modulate the magnitude of PFC-M1 IHI, whereas connectivity changed when Go/NoGo decisions were implemented in reactions during the motor tasks. Although PFC-M1 IHI is sensitive enough to be modulated by behavioral manipulations, tDCS over the lateral PFC does not have substantial modulatory effects on PFC to M1 functional connectivity, or at least not to the degree that can be detected with this measure.

<p>Accurate memory regarding the location of an object with respect to one’s own body, termed egocentric visuospatial memory, is essential for action directed towards the object. Although researchers have suggested that the brain stores information related to egocentric visuospatial memory not only in the eye-centered reference frame but also in the head-centered reference frame, experimental evidence is scarce. Here, we tested this possibility by exploiting perceptual distortion of head-centered coordinates via whole-body tilt relative to gravity. We hypothesized that if the head-centered reference frame is involved in storing the egocentric representation of a target in memory, then reproduction would be affected by this perceptual distortion. In two experiments, we asked participants to reproduce the remembered location of a visual target relative to their body. Using intervening whole-body roll rotations, we manipulated the initial (target presentation) and final (reproduction of the remembered location) body orientation in space and evaluated the effect on the reproduced location. Our results showed significant biases of the reproduced target location and perceived head/body longitudinal axis in the direction of the intervening body rotation. Importantly, their amounts of errors were correlated across participants. These results provide experimental evidence for the neural encoding and storage of information related to egocentric visuospatial memory in the head-centered reference frame.</p>

BACKGROUND: Transcranial direct current stimulation (tDCS) is a technique that can noninvasively modulate neural states in a targeted brain region. As cerebellar activity levels are associated with upper limb motor improvement after stroke, the cerebellum is a plausible target of tDCS. However, the effect of tDCS remains unclear. Here, we designed a pilot study to assess: (1) the feasibility of a study that aims to examine the effects of cerebellar tDCS combined with an intensive rehabilitation approach based on the concept of constraint-induced movement therapy (CIMT) and (2) the preliminary outcome of the combined approach on upper limb motor function in patients with stroke in the chronic stage. METHODS: This pilot study has a double-blind randomized controlled design. Twenty-four chronic stroke patients with mild to moderate levels of upper limb motor impairment will be randomly assigned to an active or sham tDCS group. The participants will receive 20 min of active or sham tDCS to the contralesional cerebellum at the commencement of 4 h of daily intensive training, repeatedly for 5 days per week for 2 weeks. The primary outcomes are recruitment, enrollment, protocol adherence, and retention rates and measures to evaluate the feasibility of the study. The secondary outcome is upper limb motor function which will be evaluated using the Action Research Arm Test, Fugl-Meyer Assessment, for the upper extremity and the Motor Activity Log. Additionally, neurophysiological and neuroanatomical assessments of the cerebellum will be performed using transcranial magnetic stimulation and magnetic resonance imaging. These assessments will be conducted before, at the middle, and after the 2-week intervention, and finally, 1 month after the intervention. Any adverse events that occur during the study will be recorded. DISCUSSION: Cerebellar tDCS combined with intensive upper limb training may increase the gains of motor improvement when compared to the sham condition. The present study should provide valuable evidence regarding the feasibility of the design and the efficacy of cerebellar tDCS for upper limb motor function in patients with stroke before a future large trial is conducted. TRIAL REGISTRATION: This study has been registered at the Japan Registry of Clinical Trials ( jRCTs042200078 ). Registered 17 December 2020.

Transcranial magnetic stimulation has been used to assess plastic changes in the cortical motor representations of targeted muscles. The present study explored the optimal settings and stimulation intensity for simultaneous motor mapping of multiple upper-limb muscles across segments. In 15 healthy volunteers, we evaluated cortical representations simultaneously from one muscle in the shoulder, two in the upper arm, two in the forearm, and two intrinsic hand muscles, using five stimulation intensities, ranging from 40% to 100% of the maximum stimulator output. We represented the motor map area acquired at each intensity as a percentage of the maximum for each muscle. We defined a motor map area between 25% and 75% of the maximum as the optimal area size with sufficient scope for both up- and down-regulation, and stimulation intensities producing the map area size within this range as the optimal intensities. We found that motor maps with optimal area sizes could be produced simultaneously for the four distal muscles of the forearm and hand in most participants when the stimulation intensity was set at 120-140% of the resting motor threshold (RMT) of the first dorsal interosseous. For the remaining three proximal muscles, motor maps with optimal area sizes were produced only in a few participants, even when using a higher intensity (180-220% RMT). These findings suggest that cortical representations can be assessed simultaneously in a group of distal muscles using a relatively low stimulation intensity, while a separate operation is required to assess that of the proximal muscles.

Objective: To examine whether alternating training with both the non-paretic and paretic sides (alternating bilateral training), expecting trial-to-trial inter-limb transfer of training effects from the nonparetic to the paretic side, improves upper-limb motor performance in post-stroke patients, compared with unilateral training involving only the paretic side.Design: An assessor-blinded pilot randomized controlled trial.Subjects: Twenty-four right-handed post-stroke patients with hemiparesis.Methods: Participants were randomly allocated to either an alternating bilateral training group or a unilateral training group (n = 12/group). Participants underwent dexterity training of the paretic arm using the Nine-Hole Peg Test, completing 10 trials/day for 7 consecutive days. The alternating bilateral training group additionally performed alternating trials with the non-paretic limb. Performance change, assessed 1 day and 1 week after the 7-day training period, was compared between groups.Results: Although the improvement was comparable in both groups at both post-training time-points, a sub-analysis in which those with left hemiparesis and those with right hemiparesis were analysed separately revealed potential benefits of the alternating bilateral training, specifically for those with left hemiparesis.Conclusion: Alternating bilateral training may augment training effects and improve upper-limb motor function in patients with left hemiparesis.

OBJECTIVE: To investigate whether automatic facial expression analysis can quantify differences in the intensity of facial responses depending on the affective stimuli in a patient with minimally conscious state (MCS). METHODS: We filmed the facial responses of a patient with MCS during the delivery of three 1-minute auditory stimuli: audio clips of comedy movies, a nurse hilariously talking, and recitation of a novel (comedy, nurse, and recitation conditions, respectively). These measures were repeated at least 13 times for each condition on different days for approximately 10 months. The intensity of being "happy" was estimated from the smiling face using a software called FaceReader. The intensity among 5 conditions including those at 2 resting conditions (pre- and poststimuli) was compared using the Kruskal-Wallis test and the Dunn-Bonferroni test for multiple comparisons. RESULTS: Significantly higher values were found in the intensity of being "happy" in the comedy and nurse conditions versus other conditions, with no significant differences between the recitation and pre- or poststimulus conditions. These findings indicate that the automated facial expression analysis can quantify differences in context-dependent facial responses in the patient recruited in this study. CONCLUSIONS: This case study demonstrates the feasibility of using automated facial expression analysis to quantitatively evaluate the differences in facial expressions and their corresponding emotions in a single patient with MCS.

Background. Stroke is one of the most common causes of physical disability worldwide. The majority of survivors experience impairment of movement, often with lasting deficits affecting hand dexterity. To date, conventional rehabilitation primarily focuses on training compensatory maneuvers emphasizing goal completion rather than targeting reduction of motor impairment. Objective. We aim to determine whether finger dexterity impairment can be reduced in chronic stroke when training on a task focused on moving fingers against abnormal synergies without allowing for compensatory maneuvers. Methods. We recruited 18 chronic stroke patients with significant hand motor impairment. First, participants underwent baseline assessments of hand function, impairment, and finger individuation. Then, participants trained for 5 consecutive days, 3 to 4 h/d, on a multifinger piano-chord-like task that cannot be performed by compensatory actions of other body parts (e.g., arm). Participants had to learn to simultaneously coordinate and synchronize multiple fingers to break unwanted flexor synergies. To test generalization, we assessed performance in trained and nontrained chords and clinical measures in both the paretic and the nonparetic hands. To evaluate retention, we repeated the assessments 1 day, 1 week, and 6 months post-training. Results. Our results showed that finger impairment assessed by the individuation task was reduced after training. The reduction of impairment was accompanied by improvements in clinical hand function, including precision pinch. Notably, the effects were maintained for 6 months following training. Conclusion. Our findings provide preliminary evidence that chronic stroke patient can reduce hand impairment when training against abnormal flexor synergies, a change that was associated with meaningful clinical benefits.

<jats:p> Motor exploration, a trial-and-error process in search for better motor outcomes, is known to serve a critical role in motor learning. This is particularly relevant during reinforcement learning where actions leading to a successful outcome are reinforced while unsuccessful actions are avoided. Although early on motor exploration is beneficial to find the correct solution, maintaining high levels of exploration later in the learning process might be deleterious. Whether and how the level of exploration changes over the course of reinforcement learning, however, remains poorly understood. Here, we evaluated temporal changes in motor exploration while healthy participants learned a reinforcement-based motor task. We defined exploration as the magnitude of trial-to-trial change in movements as a function of whether the preceding trial resulted in success or failure. Participants were required to find the optimal finger-pointing direction using binary feedback of success or failure. We found that the magnitude of exploration gradually increased over time when learning the task. Conversely, exploration remained low in participants who were unable to correctly adjust their pointing direction. Interestingly, exploration remained elevated when participants underwent a second training session, which was associated with faster relearning. These results indicate that the motor system may flexibly upregulate the extent of exploration during reinforcement learning as if acquiring a specific strategy to facilitate subsequent learning. Also, our findings showed that exploration affects reinforcement learning and vice versa, indicating an interactive relationship between them. Reinforcement-based tasks could be used as primers to increase exploratory behavior leading to more efficient subsequent learning. </jats:p>

OBJECTIVE: Cerebellar transcranial direct current stimulation (ctDCS) is a neuromodulation scheme that delivers a small current to the cerebellum. In this work, we computationally investigate the distributions and strength of the stimulation dosage during ctDCS with the aim of determining the targeted cerebellar regions of a group of subjects with different electrode montages. APPROACH: We used a new inter-individual registration method that permitted the projection of computed electric fields (EFs) from individual realistic head models (n  =  18) to standard cerebellar template for the first time. MAIN RESULTS: Variations of the EF on the cerebellar surface were found to have standard deviations of up to 55% of the mean. The dominant factor that accounted for 62% of the variability of the maximum EFs was the skin-cerebellum distance, whereas the cerebrospinal fluid volume explained 53% of the average EF distribution. Despite the inter-individual variations, a systematic tendency of the EF hotspot emerges beneath the active electrode in group-level analysis. The hotspot can be adjusted by the electrode position so that the most effective stimulation is delivered to a group of subjects. SIGNIFICANCE: Targeting specific cerebellar structures with ctDCS is not straightforward, as neuromodulation depends not only on the placement/design of the electrodes configuration but also on inter-individual variability due to anatomical differences. The proposed method permitted generalizing the EFs to a cerebellum atlas. The atlas is useful for studying the mechanisms of ctDCS, planning ctDCS and explaining findings of experimental studies.

Motor behaviors are shaped not only by current sensory signals but also by the history of recent experiences. For instance, repeated movements toward a particular target bias the subsequent movements toward that target direction. This process, called use-dependent plasticity (UDP), is considered a basic and goal-independent way of forming motor memories. Most studies consider movement history as the critical component that leads to UDP (Classen et al., 1998; Verstynen and Sabes, 2011). However, the effects of learning (i.e., improved performance) on UDP during movement repetition have not been investigated. Here, we used transcranial magnetic stimulation in two experiments to assess plasticity changes occurring in the primary motor cortex after individuals repeated reinforced and nonreinforced actions. The first experiment assessed whether learning a skill task modulates UDP. We found that a group that successfully learned the skill task showed greater UDP than a group that did not accumulate learning, but made comparable repeated actions. The second experiment aimed to understand the role of reinforcement learning in UDP while controlling for reward magnitude and action kinematics. We found that providing subjects with a binary reward without visual feedback of the cursor led to increased UDP effects. Subjects in the group that received comparable reward not associated with their actions maintained the previously induced UDP. Our findings illustrate how reinforcing consistent actions strengthens use-dependent memories and provide insight into operant mechanisms that modulate plastic changes in the motor cortex.

Purpose of the study: To evaluate the after-effects of pedaling on spinal excitability and spinal reciprocal inhibition in patients with post-stroke spastic hemiparesis. Materials and methods: Twenty stroke patients with severe hemiparesis participated in this study and were instructed to perform 7 min of active pedaling and 7 min of passive pedaling with a recumbent ergometer at a comfortable speed. H reflexes and M waves of paretic soleus muscles were recorded at rest before, immediately after and 30 min after active and passive pedaling. The Hmax/Mmax ratio and H recruitment curve were measured. Reciprocal inhibition was assessed using the soleus H reflex conditioning test paradigm. Results: The Hmax/Mmax ratio was significantly decreased after active and passive pedaling exercise. The decreased Hmax/Mmax ratio after active pedaling lasted at least for 30 min. The H recruitment curve and reciprocal inhibition did not change significantly after active or passive pedaling exercise. Conclusions: Pedaling exercise decreased spinal excitability in patients with severe hemiparesis. Pedaling may be effective in rehabilitation following stroke.

[Purpose] Post-stroke astasia is an inability to stand without external support despite having sufficient muscle strength. However, the dysfunction underlying astasia is unclear. We tested the hypothesis that astasia is the result of an abnormal bias in vertical perception, especially subjective postural vertical (SPV), mediated by somatosensory inputs. [Subjects and Methods] A patient with a right posterolateral thalamus hemorrhage had a tendency to fall toward the contralesional side during standing after 8 weeks of treatment. SPV, standing duration, and physical function were evaluated before and after a 1 week standard rehabilitation baseline period, and after a 1 week intervention period, where standing training requiring the patient to control his body orientation in reference to somatosensory inputs from his ipsilateral upper limb was added. [Results] SPV was biased toward the contralesional side before and after the 1 week baseline period. However, SPV improved into the normal range and he could stand for a longer duration after the intervention period. [Conclusion] This case suggests that abnormal SPV is one of the functional mechanisms underlying astasia, and it indicates the effectiveness of standing training with somatosensory information to improve abnormal SPV and postural disorders.

In the present study, we investigated the kinematics of object-transport movement in a downward direction using a precision grip, to elucidate how the central nervous system (CNS) takes into account object weight when making the movement, even when participants are unable to recognize the weight until they grasp the object. We found that the kinematics during transport movement were significantly changed by the object weight, even when the weight was unrecognized visually, suggesting that the CNS controls object-transport movement in a downward direction according to object weight, regardless of the visual recognizability of the weight.

Consistent repetitions of an action lead to plastic change in the motor cortex and cause shift in the direction of future movements. This process is known as use-dependent plasticity (UDP), one of the basic forms of the motor memory. We have recently demonstrated in a physiological study that success-related reinforcement signals could modulate the strength of UDP. We tested this idea by developing a computational approach that modeled the shift in the direction of future action as a change in preferred direction of population activity of neurons in the primary motor cortex. The rate of the change follows a modified temporal difference reinforcement learning algorithm, in which the learning policy is based on comparison between what reward the population experiences on a particular trial, and what it had expected on the basis of its previous learning. By using this model, we were able to characterize the nature of learning and retention of UDP. Exploring the relationship between reinforcement and UDP constitutes a crucial step toward understanding the basic blocks involved in the formation of motor memories.

Motor performance fluctuates trial by trial even in a well-trained motor skill. Here we show neural substrates underlying such behavioral fluctuation in humans. We first scanned brain activity with functional magnetic resonance imaging while healthy participants repeatedly performed a 10 s skillful sequential finger-tapping task. Before starting the experiment, the participants had completed intensive training. We evaluated task performance per trial (number of correct sequences in 10 s) and depicted brain regions where the activity changes in association with the fluctuation of the task performance across trials. We found that the activity in a broader range of frontoparietocerebellar network, including the bilateral dorsolateral prefrontal cortex (DLPFC), anterior cingulate and anterior insular cortices, and left cerebellar hemisphere, was negatively correlated with the task performance. We further showed in another transcranial direct current stimulation (tDCS) experiment that task performance deteriorated, when we applied anodal tDCS to the right DLPFC. These results indicate that fluctuation of brain activity in the nonmotor frontoparietocerebellar network may underlie trial-by-trial performance variability even in a well-trained motor skill, and its neuromodulation with tDCS may affect the task performance.

In humans, observation of others' behaviors increases corticospinal excitability (CSE), which is interpreted in the contexts of motor resonance and the "mirror neuron system" (MNS). It has been suggested that observation of another individual's behavior manifests an embodied simulation of his/her mental state through the MNS. Thus, the MNS may involve understanding others' intentions of behaviors, thoughts, and emotions (i.e., social cognition), and may therefore exhibit a greater response when observing human-interactive behaviors that require a more varied and complex understanding of others. In the present study, transcranial magnetic stimulation was applied to the primary motor cortex of participants observing human-interactive behaviors between two individuals (c.f. one person reaching toward an object in another person's hand) and non-interactive individual behavior (c.f. one person reaching toward an object on a dish). We carefully controlled the kinematics of behaviors in these two conditions to exclude potential effects of MNS activity changes associated with kinematic differences between visual stimuli. Notably, motor evoked potentials, that reflect CSE, from the first dorsal interosseous muscle exhibited greater amplitude when the participants observed interactive behaviors than when they observed non-interactive behavior. These results provide neurophysiological evidence that the MNS is activated to a greater degree during observation of human-interactive behaviors that contain additional information about the individuals' mental states, supporting the view that the MNS plays a critical role in social cognition in humans. (C) 2015 Elsevier Inc. All rights reserved.

Previously, we reported that cerebellar transcranial magnetic stimulation (C-TMS) facilitates spinal motoneuronal excitability in resting humans. In this study, we aimed to characterize the descending pathway that is responsible for the C-TMS-associated cerebellar spinal facilitation. We evaluated the effect of C-TMS on ipsilateral soleus Ia presynaptic inhibition (PSI) and reciprocal inhibition (RI) because the vestibulospinal and reticulospinal tracts project from the cerebellum to mediate spinal motoneurons via interneurons associated with PSI. PSI and RI were measured with a soleus H-reflex test following operant conditioning using electrical stimulation of the common peroneal nerve. C-TMS was delivered before test tibial nerve stimulation with conditioning-test interstimulus intervals of 110 ms. C-TMS did not generate motor-evoked potentials, and it did not increase electromyography activity in the ipsilateral soleus muscle, indicating that C-TMS does not directly activate the corticospinal tract and motoneurons. However, C-TMS facilitated the ipsilateral soleus H-reflex and reduced the amount of soleus Ia PSI, but not RI. These findings indicate that C-TMS may facilitate the excitability of the spinal motoneuron pool via the vestibulospinal or reticulospinal tracts associated with PSI. Cerebellar spinal facilitation may be useful for assessing the functional connectivity of the cerebellum and vestibular nuclei or reticular formation. Copyright (c) 2015 Wolters Kluwer Health, Inc. All rights reserved.

In daily life, we often try to learn motor actions by imitating others' actions. Motor imitation requires us to simultaneously map an observed action onto a motor program used to perform that action. This sensorimotor associative experience can plastically modulate the mirror property of the human mirror system, which has a role in matching observed actions directly with the observer's motor programs, to enhance the association between observed and performed actions. In the present study, we investigated the effects of handedness on the mirror property. Healthy left- and right-handed individuals performed a motor imitation task. They were required to imitate hand actions with their dominant hand as quickly and accurately as possible in response to pictures of a left and right hand. Reaction times (RTs) for imitating the hand actions were evaluated. Under the condition where the hand pictures were presented as if facing the participant, we found that, in left-handed participants, RTs for imitating right-handed actions were significantly shorter than those for imitating left-handed actions. Under the same conditions in right-handers, similar differences in RTs when presented left- and right-handed actions were not observed. These findings demonstrate that the imitative responses for left- and right-handed actions are differently facilitated depending on the handedness of the observer, indicating an effect of handedness on the development of mirror systems. The mirror property in left- and right-handers is likely modulated in a different manner by different sensorimotor associative experiences throughout their daily lives. (C) 2014 Elsevier Ireland Ltd. All rights reserved.

We investigated whether cerebellar transcranial magnetic stimulation (C-TMS) facilitates the excitability of the ipsilateral soleus motoneuron pool in resting humans, and whether the facilitation is modulated by a task that promotes cerebellar activity. A test tibial nerve stimulus evoking the H-reflex from the right soleus muscle was delivered before or after conditioning C-TMS in prone individuals. The amplitude of the H-reflex was significantly increased at conditioning-test interstimulus intervals of 110, 120, and 130 ms. Furthermore, we revealed that this facilitation effect was inhibited while the individuals tapped their right index finger. These findings indicate that C-TMS facilitates spinal motoneuronal excitability with an similar to 100ms latency in resting humans, and that this cerebellar spinal facilitation is modulated by a task that might increase cerebellar activity. Cerebellar spinal facilitation could thus be useful for assessing the excitability of the cerebellum, or the cerebellar output to spinal motoneurons. (C) 2014 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.

【目的】人工膝関節置換術(以下,TKA)後の膝関節周囲の皮膚可動性の特徴をあきらかにするとともに,術後に獲得される膝関節屈曲可動域との関係性を検証した。【方法】対象はTKA術後患者20名(平均78.1±7.4歳),健常高齢者10名(平均71.8±8.7歳)とした。皮膚可動性を評価するため,膝関節前面の皮膚上にマークし,膝関節を他動的に60度,90度,最終屈曲位にしたときのマーク間距離(縦方向,横方向)を測定した。膝関節屈曲角度120度を基準にTKA術後患者を2群に分類し,健常高齢者を含めた3群間の皮膚可動性を比較した。【結果】TKA術後患者は,膝蓋骨上部付近の縦方向の皮膚可動性が健常高齢者に比べて有意に低下していた。一方で,屈曲120度未満群と以上群との間に有意差を認めなかった。【結論】TKA術後の術創部周囲の皮膚は,健常高齢者に比べて可動性が顕著に低下していた。しかし,皮膚可動性はTKA術後に獲得できる屈曲可動域に対する強い制限因子ではないことが示唆された。

Procedural motor learning includes a period when no substantial gain in performance improvement is obtained even with repeated, daily practice. Prompted by the potential benefit of high-frequency transcutaneous electrical stimulation, we examined if the stimulation to the hand reduces redundant motor activity that likely exists in an acquired hand motor skill, so as to further upgrade stable motor performance. Healthy participants were trained until their motor performance of continuously rotating two balls in the palm of their right hand became stable. In the series of experiments, they repeated a trial performing this cyclic rotation as many times as possible in 15 s. In trials where we applied the stimulation to the relaxed thumb before they initiated the task, most reported that their movements became smoother and they could perform the movements at a higher cycle compared to the control trials. This was not possible when the dorsal side of the wrist was stimulated. The performance improvement was associated with reduction of amplitude of finger displacement, which was consistently observed irrespective of the task demands. Importantly, this kinematic change occurred without being noticed by the participants, and their intentional changes of motor strategies (reducing amplitude of finger displacement) never improved the performance. Moreover, the performance never spontaneously improved during one-week training without stimulation, whereas the improvement in association with stimulation was consistently observed across days during training on another week combined with the stimulation. The improved effect obtained in stimulation trials on one day partially carried over to the next day, thereby promoting daily improvement of plateaued performance, which could not be unlocked by the first-week intensive training. This study demonstrated the possibility of effectively improving a plateaued motor skill, and pre-movement somatic stimulation driving this behavioral change.

Purpose: Currently, to record underwater surface electromyography (EMG), electrodes are covered with water-proof tape. For short-term measurement, waterproof tape prevents electrical leakage. However, during long-term measurement, water or sweat can contact the electrodes, changing the measurement conditions and gradually affecting the EMG data. The purpose of present study was to devise a novel method for prolonged underwater EMG recording, which estimate dry-land EMG from underwater EMG recorded by non-waterproofed electrodes using system identification techniques. Method: One healthy male participated in this study. System identification was used to convert underwater EMG signals to the estimated dry-land signals. Transfer functions were derived using two pairs of surface recording electrodes on the same muscle in parallel. System input was the EMG recorded using non-waterproofed electrodes the output was the signal recorded underwater using waterproofed electrodes (supposed to be the same as dry-land signals). To examine the validity of the present method, three experiments were conducted. Result: There was a high positive correlation between the estimated dry-land EMG based on the non-water-proofed electrodes and the EMG obtained using waterproofed electrodes. To test the validity of long-term recording using the novel method, the estimated dry-land EMG signals were measured during 30 minutes of underwater stepping and were stable. Conclusion: The novel method using non-waterproofed electrodes with system identification techniques eliminated the effect of changes in measurement conditions and appears effective for long-term, underwater surface EMG recording.