Published papers

Fujii S, Kudo K, Ohtsuki T, Oda S. Intrinsic constraint of asymmetry acting as a control parameter on rapid, rhythmic bimanual coordination: a study of professional drummers and nondrummers. J Neurophysiol 104: 2178-2186, 2010. First published August 11, 2010; doi:10.1152/jn.00882.2009. Expert musicians show experience-dependent reduced asymmetry in the structure of motor-related brain areas and in the maximum tapping frequency between the hands. Therefore we hypothesized that a reduced hand-skill asymmetry is strongly related to rapid and rhythmical bimanual coordination and developed a dynamical model including a symmetry-breaking parameter Delta omega, for human bimanual coordination. We conducted unimanual and bimanual drumming experiments to test the following model predictions. 1) The asymmetry in the maximum tapping frequency is more pronounced in nondrummers than that in drummers. If so, 2) a larger number of phase wanderings (i.e., succession of taps by the same hand), 3) larger SD of the relative phase between the hands (SD phi), and 4) larger deviation of mean relative phase (mean phi) from 180 degrees would be observed in nondrummers than that in professional drummers during antiphase bimanual drumming at the maximum speed. In a unimanual tapping task, the asymmetry in maximum tapping frequency of nondrummers was more pronounced than that of professional drummers. In a bimanual coordination task, phase wanderings were observed only in nondrummers and SD phi of the nondrummers is significantly larger than that of professional drummers. On the other hand, there was no significant difference between the mean phi of the two groups. All these observations were successfully reproduced by changing Delta omega, which corresponded to the asymmetry in the maximum tapping frequency. These results support the hypothesis indicating that the prominent bimanual coordination pattern emerges spontaneously after a nonspecific change in Delta omega or symmetry restoration of the nonlinear dynamical systems.

Motor learning is a process whereby the acquisition of new skills occurs with practice, and can be influenced by the provision of feedback. An important question is what frequency of feedback facilitates motor learning. The guidance hypothesis assumes that the provision of less augmented feedback is better than more because a learner can use his/her own inherent feedback. However, it is unclear whether this hypothesis holds true for all types of augmented feedback, including for example sonified information about performance. Thus, we aimed to test what frequency of augmented sonified feedback facilitates the motor learning of a novel joint coordination pattern. Twenty healthy volunteers first reached to a target with their arm (baseline phase). We manipulated this baseline kinematic data for each individual to create a novel target joint coordination pattern. Participants then practiced to learn the novel target joint coordination pattern, receiving either feedback on every trial i.e., 100% feedback (n = 10), or every other trial, i.e., 50% feedback (n = 1 0; acquisition phase). We created a sonification system to provide the feedback. This feedback was a pure tone that varied in intensity in proportion to the error of the performed joint coordination relative to the target pattern. Thus, the auditory feedback contained information about performance in real-time (i.e., "concurrent, knowledge of performance feedback"). Participants performed the novel joint coordination pattern with no-feedback immediately after the acquisition phase (immediate retention phase), and on the next day (delayed retention phase). The root-mean squared error (RMSE) and variable error (VE) of joint coordination were significantly reduced during the acquisition phase in both 100 and 50% feedback groups. There was no significant difference in VE between the groups at immediate and delayed retention phases. However, at both these retention phases, the 100% feedback group showed significantly smaller RMSE than the 50% group. Thus, contrary to the guidance hypothesis, our findings suggest that the provision of more, concurrent knowledge of performance auditory feedback during the acquisition of a novel joint coordination pattern, may result in better skill retention.

リズミカルなストリートダンスにおける身体運動制御について、ダイナミカルシステムアプローチの観点から概説し、今後の研究の展望について述べた。

Given that approximately one-third of patients with schizophrenia do not respond to antipsychotics, different neurobiological bases may underlie treatment resistance in schizophrenia. Previous studies showed that treatment response is associated with both frontostriatal connectivity and glutamatergic neurometabolite levels in the caudate in patients with schizophrenia, which leads to the hypothesis that the relationship between them may be altered, specifically in patients with treatment-resistant schizophrenia (TRS). Employing analyses of covariance and subsequent partial correlation analyses, we compared the relationship between glutamate+glutamine (Glx) levels in the caudate and fractional anisotropy (FA) values in the tract between the dorsolateral prefrontal cortex and caudate in 19 patients with TRS, 20 patients responsive to first-line antipsychotics (FL-Resp), and 19 healthy controls (HCs). TRS was defined by severe positive symptomatology despite first-line antipsychotic treatment. Patients with TRS had lower FA values in the bilateral frontostriatal tracts than patients with FL-Resp and HCs (P < .001), while no group differences were found in caudate Glx levels. There was a significant frontostriatal FA value-by-group interaction on caudate Glx levels (F = 7.37, P = .009). Frontostriatal FA values positively correlated with caudate Glx levels in HCs (r = −.55, P = .028), while they were negatively associated with caudate Glx levels in the TRS group (r = .53, P = .043). Furthermore, in the FL-Resp group, frontostriatal FA values did not significantly correlated with caudate Glx levels. The altered relationship between white matter integrity and the glutamate system in the frontostriatal circuit in the TRS group may reflect the pathophysiology underlying treatment response/resistance in schizophrenia.

The aim of this study is to establish the effects of stick use on rhythmic bimanual coordination in drummers. Eighteen drummers performed a rapid antiphase coordination task using their fingers and handheld drumsticks. We found no significant differences in the speed of tapping between finger and stick-use tapping, while stick-use tapping had a larger peak force and smaller variability in coordination pattern than finger tapping. As a consequence, the quotient of the number of taps divided by the variability of coordination pattern, named the bimanual performance quotient, was higher for stick-use tapping than for finger tapping. A significant correlation was found between years of drumming experience and the bimanual performance quotient for both finger and stick-use tapping, but not between the years of drumming experience and the degree of improvement in the bimanual performance quotient with stick use relative to finger tapping. These results indicate that stick use enhances drummers' bimanual coordination during rapid alternate tapping, whereas the degree of improvement with stick use does not depend on drumming experience.

Drummers achieve impressive musical performance by using drumsticks. The present study investigated the effect of drumstick use on rapid unimanual tapping performance. 17 drummers tapped a force transducer as fast as possible for 10 sec. with a finger and a drumstick. No significant difference between finger and stick tapping was found for tapping speed and variability of peak force, but there were significant differences in contact time with the tapping surface, mean peak force, and intertap interval variability: Stick tapping had a shorter contact time, a larger peak force, and more stable intertap interval than did finger tapping. Thus, stick use makes it possible to produce a larger impact force and enhances the ability to control timing during rapid manual movement, allowing drummers to play drums powerfully and stably, which is clearly important for the role they have in controlling or enhancing musical rhythm.

Understanding reactive responses to unexpected perturbation is fundamental to research on falls and their prevention. In this Study, seven healthy young males walked along a walkway with and without a completely unexpected loss of ground support that was made by removing a wooden board (6.5 cm high) mounted oil the walkway. Electromyography (EMG), ground reaction forces, and knee and ankle kinematics were recorded and comprehensively analyzed to investigate the corrective postural response to the perturbation. Three sequential strategies were observed. First, the fastest response was the reflexive muscle activity of the perturbed ankle, which we argue was evoked and enhanced by the absence of the expected somatosensory afferents at the expected heel contact. We also demonstrated that rapid soleus activity partially contributed to absorbing the impact of the actual touchdown. Second, after the touchdown, we argue that the central nervous system may reset the gait rhythm to permit continued walking by delaying the subsequent take-off. As a result, the duration of the total stance phase was identical to that recorded during normal walking. Third, we observed an adaptive locomotion to surmount the hole; both knees were more flexed than normal in order to allow the subject to withdraw the perturbed leg from the hole. (C) 2008 Elsevier B.V. All rights reserved.

ストリートダンスの世界チャンピオン、ダンサー、ノンダンサーの指運動がメトロノーム拍子に対してどの程度同期しているのかを調査し、ストリートダンスの世界チャンピオンは多様なテンポ下で運動速度のピークタイミングとビートタイミングを安定して同期させていることを明らかにした。

The uniqueness of human music relative to speech and animal song has been extensively debated, but rarely directly measured. We applied an automated scale analysis algorithm to a sample of 86 recordings of human music, human speech, and bird songs from around the world. We found that human music throughout the world uniquely emphasized scales with small-integer frequency ratios, particularly a perfect 5th (3:2 ratio), while human speech and bird song showed no clear evidence of consistent scale-like tunings. We speculate that the uniquely human tendency toward scales with small-integer ratios may relate to the evolution of synchronized group performance among humans.

Music throughout the world varies greatly, yet some musical features like scale structure display striking crosscultural similarities. Are there musical laws or biological constraints that underlie this diversity? The “vocal mistuning” hypothesis proposes that cross-cultural regularities in musical scales arise from imprecision in vocal tuning, while the integer-ratio hypothesis proposes that they arise from perceptual principles based on psychoacoustic consonance. In order to test these hypotheses, we conducted automatic comparative analysis of 100 children’s and adult songs from throughout the world. We found that children’s songs tend to have narrower melodic range, fewer scale degrees, and less precise intonation than adult songs, consistent with motor limitations due to their earlier developmental stage. On the other hand, adult and children’s songs share some common tuning intervals at small-integer ratios, particularly the perfect 5th (~3:2 ratio). These results suggest that some widespread aspects of musical scales may be caused by motor constraints, but also suggest that perceptual preferences for simple integer ratios might contribute to cross-cultural regularities in scale structure. We propose a “sensorimotor hypothesis” to unify these competing theories.

Aim: Stress‐related disorders and severe stress exposure can cause atrophy of the whole hippocampus and its subfields. However, the impact of stress coping strategies on the hippocampus remains unclear. Therefore, we aimed to examine the relation between approach‐ and avoidance‐oriented coping strategies and hippocampal volume in elderly persons. Methods: A total of 1045 elderly persons living in Arakawa‐ward, Tokyo (mean ± SD age: 72.8 ± 5.2 years; 569 females [54.4%]) were included in the study and completed several questionnaires and face‐to‐face interviews and underwent magnetic resonance imaging. Approach‐ or avoidance‐oriented coping strategies were assessed with the Stress and Coping Inventory, while cognitive function and depressive symptoms were assessed with the Mini‐Mental State Examination and Geriatric Depression Scale, respectively. The volume of the whole hippocampus on T1‐weighted images was delineated and calculated using FreeSurfer 6.0. Multiple regression analyses were performed to examine the relation between Stress and Coping Inventory scores and whole hippocampal volume. Results: Approach‐oriented coping strategy scores were positively correlated with whole hippocampal volume. Furthermore, these relations remained significant after controlling for the influence of cognitive function and depressive symptoms on these volumetric variables. In contrast, avoidance‐oriented coping strategy scores were not correlated with whole hippocampal volume. Conclusion: This study demonstrated that hippocampal volume may be associated with the approach‐oriented coping strategy; therefore, this strategy may preserve hippocampal volume in the elderly.

Background: The neural basis of treatment-resistant schizophrenia (TRS) remains unclear. Previous neuroimaging studies suggest that aberrant connectivity between the anterior cingulate cortex (ACC) and default mode network (DMN) may play a key role in the pathophysiology of TRS. Thus, we aimed to examine the connectivity between the ACC and posterior cingulate cortex (PCC), a hub of the DMN, computing isolated effective coherence (iCoh), which represents causal effective connectivity. Methods: Resting-state electroencephalogram with 19 channels was acquired from seventeen patients with TRS and thirty patients with non-TRS (nTRS). The iCoh values between the PCC and ACC were calculated using sLORETA software. We conducted four-way analyses of variance (ANOVAs) for iCoh values with group as a between-subject factor and frequency, directionality, and laterality as within-subject factors and post-hoc independent t-tests. Results: The ANOVA and post-hoc t-tests for the iCoh ratio of directionality from PCC to ACC showed significant findings in delta (t = 7.659, p = 0.008) and theta (t = 8.066, p = 0.007) bands in the left side (TRS < nTRS). Conclusion: Left delta and theta PCC and ACC iCoh ratio may represent a neurophysiological basis of TRS. Given the preliminary nature of this study, these results warrant further study to confirm the importance of iCoh as a clinical indicator for treatment-resistance. 45 45

バスケットボールの熟練者と未熟練者のドリブルパフォーマンスの時空間的特性の違いについて明らかにした。