Published papers

最速タッピング課題のパフォーマンス分析と非線形力学系モデリングを用いた数理的検討によって、ドラム奏者の手の機能的左右差について研究した。

最速タッピング課題を用いて、トップドラマーのタップ間隔とタップ力の解析を行い、トップドラマーの最速タッピングパフォーマンスを調査した。

This study investigated performance and wrist muscle activity during rapid-repetitive unimanual tapping with a drumstick in right-handed drummers and nondrummers. Analyses of performances revealed no difference in tapping frequency and peak tap force between drummers and nondrummers, although the drummers showed less variability in intertap interval than the nondrummers. Analyses of the electromyographic (EMG) data obtained by recording the activity of the flexor carpi ulnalis and the extensor carpi radialis muscles of the right wrist revealed several distinct differences between the two groups: the drummers showed a lower level of muscle cocontraction together with an earlier decline of wrist flexor muscle activity and a smaller variability of muscle activation time in the wrist flexors compared with the nondrummers. We suggest that these characteristics in wrist muscle activity in the drummers have been acquired following extensive practice for the efficient use of wrist muscles and stable drumming performance.

Development of motion capture technology has enabled the measurement of body movements over long periods of time in daily life. Although accelerometers have been used as primary sensors, problems arise when they are used to measure the movements of infants. Because infants and caregivers interact frequently, accelerometer data from infants may be significantly distorted by a caregiver’s movement. To overcome this problem, a strain sensor suit was developed for infants to measure flexion and extension movements of the limbs. A case study was performed to analyze the strain sensor data of an infant in relation to the accelerometer data of the infant’s and a caregiver’s body under various types of infant–caregiver interaction. The results demonstrated that the strain sensor data had low correlation with the accelerometer data of the infant and caregiver while the accelerometer data between infant and caregiver had higher correlation. This suggests that the strain sensor is suitable to detect limbs’ angular displacements mostly independent from the translational body movements exerted by a caregiver.

Previous diffusion tensor imaging (DTI) studies have reported white matter alterations in patients with schizophrenia. Notably, one third of this population does not respond to first-line antipsychotics and is thus referred to as treatment-resistant schizophrenia (TRS). Despite potentially distinct neural bases between TRS and non-TRS, few studies have compared white matter integrity between these groups. In order to reflect clinical picture of TRS, we enrolled TRS patients who had severe symptoms. According to the consensus criteria for TRS. TRS was defined by severe positive symptomatology despite optimal antipsychotic treatment. Fractional anisotropy (FA), an index of white matter integrity, was examined by DTI and analyzed with tract-based spatial statistics in 24 TRS patients (mean PANSS = 108.9), 28 non-TRS patients (mean PANSS = 50.0), and 27 healthy controls (HCs) for group comparison. Additionally, correlation analyses were conducted between FA values and symptomatology. The TRS group had lower FA values in multiple tracts (cerebral peduncle, corona radiata, corpus callosum, external and internal capsules, posterior thalamic radiation, sagittal stratum, superior longitudinal fasciculus, tapetum, and uncinate fasciculus) compared to the HC group as well as the non-TRS group (p < .05; family-wise error-corrected), while no differences were found between the non-TRS and HC groups. In the TRS group, FA values in most of the tracts (other than the left anterior limb of internal capsule, left cerebral peduncle, and right uncinate fasciculus) were negatively correlated with the Positive and Negative Syndrome Scale total scores, and negative and general symptom scores. No such relationships were found in the non-TRS group. The identified white matter integrity deficits may reflect the pathophysiology of TRS.

音楽リズムと発話リズムの知覚生成がどのような神経基盤により実現されるのかを概説し、発話言語リハビリテーションにおけるリズムの役割について「SEP Hypothesis」を提唱した。

ハーバード大学と共同でヒトのリズム知覚生成能力の個人差を評価するためのテスト（ハーバードビート評価テスト、Harvard Beat Assessment Test: HBAT）を開発し、リズム知覚生成能力の乖離性の評価を可能にした。

THE PRESENT STUDY EXAMINED THE SYNCHRONIZATION error (SE) of drum kit playing by professional drummers with an auditory metronome, focusing on the effects of motor effectors and tempi. Fifteen professional drummers attempted to synchronize a basic drumming pattern with a metronome as precisely as possible at tempi of 60, 120, and 200 beats per minute (bpm). In the 60 and 120 bpm conditions, the right hand (high-hat cymbals) showed small mean SE (similar to 2 ms), whereas the left hand (snare drum) and right foot (bass drum) preceded the metronome by about 10 ms. In the 200 bpm condition, the right hand was delayed by about 10 ms relative to the metronome, whereas the left hand and right foot showed small SE (similar to 1 ms). The absolute values of SE were smaller than those reported in previous tapping studies. In addition, the time series of SE were significantly correlated across the motor effectors, suggesting that each limb synchronized in relation to the other limbs rather than independently with the metronome.

Studies of rapid unimanual tapping have assumed that the human rate limit for voluntary rhythmic movement is 5-7 Hz, which corresponds to an inter-tap interval (ITI) of 150-200 ms. In fact, the winner of a recent contest to find the world's fastest drummer (WFD) can perform such movements using a handheld drumstick at 10 Hz, which corresponds to an ITI of 100 ms. Because the contest measured only the number of taps by the WFD, we examined the stability of the M and the underlying wrist muscle activity of the WFD. By comparing the performance and wrist muscle activity of the WFD with those of two control groups (non-drummers (NDs) and ordinary skilled drummers (ODs)), we found that the WFD had a relatively stable ITI and more pronounced reciprocal wrist muscle activity during the 10-Hz performance. Our result indicates that very fast, stable tapping performance can be achieved by keeping the wrist joint compliant rather than stiff. (C) 2009 Elsevier Ireland Ltd. All rights reserved.

The purpose of this study was to investigate tapping speed asymmetry in 13 right-handed drummers and 13 right-handed nondrummers. The participants executed single-hand tapping with a stick as fast as possible for 10 sec. with the left and right hand. There was no significant difference in the tapping speed of the right hand between the drummers and the nondrummers, whereas in the left hand, the drummers tapped significantly faster than the nondrummers. Drummers showed less tapping speed asymmetry than nondrummers. These results suggest that the tapping speed of the nonpreferred hand progressed nearly to the level of the preferred hand through daily drum training.

媒介分析を用いて、ストリートダンサーとノンダンサーの聴覚運動連関と速度限界の違いが生じる要因について明らかにした。

From expert percussionists to individuals who cannot dance, there are widespread differences in people's abilities to perceive and synchronize with a musical beat. The aim of our study was to identify candidate brain regions that might be associated with these abilities. For this purpose, we used Voxel-Based-Morphometry to correlate inter-individual differences in performance on the Harvard Beat Assessment Tests (H-BAT) with local inter-individual variations in gray matter volumes across the entire brain space in 60 individuals. Analysis revealed significant co-variations between performances on two perceptual tasks of the Harvard Beat Assessment Tests associated with beat interval change discrimination (faster, slower) and gray matter volume variations in the cerebellum. Participant discrimination thresholds for the Beat Finding Interval Test (quarter note beat) were positively associated with gray matter volume variation in cerebellum lobule IX in the left hemisphere and crus I bilaterally. Discrimination thresholds for the Beat Interval Test (simple series of tones) revealed the tendency for a positive association with gray matter volume variations in crus I/II of the left cerebellum. Our results demonstrate the importance of the cerebellum in beat interval discrimination skills, as measured by two perceptual tasks of the Harvard Beat Assessment Tests. Current findings, in combination with evidence from patients with cerebellar degeneration and expert dancers, suggest that cerebellar gray matter and overall cerebellar integrity are important for temporal discrimination abilities.

Purpose: After practice, augmented feedback is the most important factor that facilitates motor learning. We assess the potential effectiveness of two types of augmented auditory feedback on the re-learning of arm reaching in individuals with stroke: (a) real-time knowledge of performance (KP) feedback and (b) rhythmic cueing in the form of knowledge of results (KR) feedback. Method: Five participants with stroke underwent short-term practice, reaching with their affected arm with KP, KR and no feedback, on separate days. We assessed range of motion of the upper extremity (shoulder, elbow) and trunk, mean error and variability of the performed trajectory, and movement time, before and after training. Results: All participants benefitted from practice with feedback, though the effects varied across participants and feedback type. In three participants, KP feedback increased elbow extension and reduced compensatory trunk flexion. In four participants, KR feedback reduced movement time taken to perform the reach. Of note, one participant benefitted mostly from KP feedback, which increased shoulder flexion and elbow extension, and decreased compensatory trunk flexion and mean error. Conclusions: Within day practice with augmented auditory feedback improves reaching in individuals with stroke. This warrants further investigation with longer practice periods in a larger sample size. Implications for Rehabilitation After practice, augmented feedback is the second most important factor that facilitates motor learning. Music-based augmented auditory feedback has potential to enhance reaching abilities in individuals with stroke. Future studies are warranted to evaluate the long-term effectiveness of this feedback over a longer training period in a larger sample size.

Dancing and singing to music involve auditory-motor coordination and have been essential to our human culture since ancient times. Although scholars have been trying to understand the evolutionary and developmental origin of music, early human developmental manifestations of auditory-motor interactions in music have not been fully investigated. Here we report limb movements and vocalizations in three- to four-months-old infants while they listened to music and were in silence. In the group analysis, we found no significant increase in the amount of movement or in the relative power spectrum density around the musical tempo in the music condition compared to the silent condition. Intriguingly, however, there were two infants who demonstrated striking increases in the rhythmic movements via kicking or arm-waving around the musical tempo during listening to music. Monte-Carlo statistics with phase-randomized surrogate data revealed that the limb movements of these individuals were significantly synchronized to the musical beat. Moreover, we found a clear increase in the formant variability of vocalizations in the group during music perception. These results suggest that infants at this age are already primed with their bodies to interact with music via limb movements and vocalizations.

Spike shape analysis (SSA) is a method to infer motor unit (MU) activity by examining interference pattern of surface electromyography (sEMG). SSA has succeeded to assess neuromuscular adaptations after dynamic training: however, it has not been used to assess muscle activities during the dynamic movements as seen in music performance. The present study used SSA to investigate sEMG activities of wrist flexor and extensor muscles in the winner of a contest to find the world's fastest drummer (WFD) during performing rhythmic wrist flexion/extension movements with one hand using a handheld drumstick. SSA measures of the WFD were compared with those in the two control groups: non-drummers (NDs) and ordinary drummers (ODs). We found that the WFD showed significantly high mean spike frequency (MSF), short mean spike duration (MSD), and small mean number of peaks per spike (MNPPS) compared with the control groups. These results suggest that the WFD had exceptional MU activity such as higher MU discharge rate, more MU recruitment, and/or higher MU synchronization to achieve extraordinary fast 10-Hz drumming performance. SSA will be useful to investigate the muscle activity seen in music performance. (C) 2012 Elsevier Ireland Ltd. All rights reserved.

The winner of an international contest to find the world's fastest drummer (WFD) can perform repetitive wrist tapping movements with one hand using a handheld drumstick at 10 Hz, much faster than the maximum tapping frequency of 5-7 Hz in the general population. The muscle activity facilitating this improved performance, however, has only recently been explored. The present study investigated the rise rate and timing variability of surface electromyographic (EMG) activity of wrist flexor/extensor muscles in the WFD, and compared them with those in two control groups: non-drummers (NDs) and ordinary drummers (ODs). The WFD showed more rapid EMG amplitude rise, earlier decline of EMG activity, and more stable muscle activation time than the NDs and ODs. In addition, there was a significant correlation between the EMG rise rate and the duration of drum training in the group of drummers (i.e., ODs and WFD). These results indicate that the 10-Hz performance of the WFD was achieved by a 'sharper' and 'less noisy' burst pattern of wrist muscles, and that drum training would have the effect to increase the speed of development of muscle tension. (C) 2011 Elsevier Ltd. All rights reserved.

While novices who are unfamiliar to a new motor skill typically show variable and unstable movements, highly skilled experts show a stable and accurate performance. These distinct differences in motor control between experts and novices have led researchers to hypothesize that neuromotor noise is reduced in the process of motor skill acquisition. On the other hand, it should be noted that novices’ movements have other characteristics; they are habituated and stereotyped. In this review, we discuss the principles governing spatiotemporal organization of movements in novices and experts while solving specific motor problems under varied conditions, by introducing experimental and theoretical studies that use neurophysiological techniques such as electromyography, functional magnetic resonance imaging, and transcranial magnetic stimulation, and mathematical models such as stochastic and dynamical models. On the basis of the findings from a variety of perceptual-motor skills (e.g., ballthrowing, badminton smash, long-distance running, piano and drum performance, street dance, a popular hand game of rock-paper-scissors, and temporal order judgement task), we argue that the novices’ characteristic movement patterns were organized under specific constraints and typical strategy, without which the variability would increase even more, while experts’ movements were organized with functional and compensatory variability that can drive out erroneous noise variability. We also showed that in a particular type of interlimb coordination, skilled and unskilled movement patterns could be seamlessly described as the time evolution of nonlinear and self-organized dynamical systems, suggesting that the dynamical systems approach is a major candidate for understanding the principle underlying organization of experts’ and novices’ movements.

The aim of this study was to investigate the spatiotemporal characteristics of rhythmic, stationary basketball bouncing in skilled and unskilled adult basketball players. Skilled (n=12) and unskilled (n=11) basketball players were asked to bounce a basketball every 700 msec. in as temporally stable and spatially accurate a manner as possible, while keeping their eyes fixed straight ahead. Spatial analyses revealed a lower variability of the ball bouncing point and less deviation from a target point in the performance of skilled players compared to unskilled players. Temporal analyses revealed no significant difference in variability of the interbounce interval in skilled versus unskilled players. However, skilled players had longer and more consistent contact time between hand and ball compared to the unskilled players. These results suggest that longer and more consistent hand contact with the ball play an important role in spatial control of basketball bouncing position.