Neuromuscular and biomechanical functions subserving finger dexterity in musicians

Neural correlates of bilateral proprioception and adaptation with training

Bilateral proprioception includes the ability to sense the position and motion of one hand relative to the other, without looking. This sensory ability allows us to perform daily activities seamlessly, and its impairment is observed in various neurological disorders such as cerebral palsy and stroke. It can undergo experience-dependent plasticity, as seen in trained piano players. If its neural correlates were better understood, it would provide a useful assay and target for neurorehabilitation for people with impaired proprioception. We designed a non-invasive electroencephalography-based paradigm to assess the neural features relevant to proprioception, especially focusing on bilateral proprioception, i.e., assessing the limb distance from the body with the other limb. We compared it with a movement-only task, with and without the visibility of the target hand. Additionally, we explored proprioceptive accuracy during the tasks. We tested eleven Controls and nine Skilled musicians to assess whether sensorimotor event-related spectral perturbations in μ (8-12Hz) and low-β (12-18Hz) rhythms differ in people with musical instrument training, which intrinsically involves a bilateral proprioceptive component, or when new sensor modalities are added to the task. The Skilled group showed significantly reduced μ and low-β suppression in bilateral tasks compared to movement-only, a significative difference relative to Controls. This may be explained by reduced top-down control due to intensive training, despite this, proprioceptive errors were not smaller for this group. Target visibility significantly reduced proprioceptive error in Controls, while no change was observed in the Skilled group. During visual tasks, Controls exhibited significant μ and low-β power reversals, with significant differences relative to proprioceptive-only tasks compared to the Skilled group-possibly due to reduced uncertainty and top-down control. These results provide support for sensorimotor μ and low-β suppression as potential neuromarkers for assessing proprioceptive ability. The identification of these features is significant as they could be used to quantify altered proprioceptive neural processing in skill and movement disorders. This in turn can be useful as an assay for pre and post sensory-motor intervention research.

Optical Myography-Based Sensing Methodology of Application of Random Loads to Muscles during Hand-Gripping Training

Hand-gripping training is important for improving the fundamental functions of human physical activity. Bernstein's idea of "repetition without repetition" suggests that motor control function should be trained under changing states. The randomness level of load should be visualized for self-administered screening when repeating various training tasks under changing states. This study aims to develop a sensing methodology of random loads applied to both the agonist and antagonist skeletal muscles when performing physical tasks. We assumed that the time-variability and periodicity of the applied load appear in the time-series feature of muscle deformation data. In the experiment, 14 participants conducted the gripping tasks with a gripper, ball, balloon, Palm clenching, and paper. Crumpling pieces of paper (paper exercise) involves randomness because the resistance force of the paper changes depending on the shape and layers of the paper. Optical myography during gripping tasks was measured, and time-series features were analyzed. As a result, our system could detect the random movement of muscles during training.

Active perceptual learning involves motor exploration and adaptation of predictive sensory integration

Our ability to perceive both externally generated and self-generated sensory stimuli can be enhanced through training, known as passive and active perceptual learning (APL). Here, we sought to explore the mechanisms underlying APL by using active haptic training (AHT), which has been demonstrated to enhance the somatosensory perception of a finger in a trained motor skill. In total 120 pianists participated in this study. First, AHT reorganized the muscular coordination during the piano keystroke. Second, AHT increased the relative reliance on afferent sensory information relative to predicted one, in contrast to no increment of overall perceptual sensitivity. Finally, AHT improved feedback movement control of keystrokes. These results suggest that APL involves active exploration and adaptation of predictive sensory integration, which underlies the co-enhancement of active perception and feedback control of movements of well-trained individuals.

Behavioral and physiological fatigue-related factors influencing timing and force control learning in pianists

Optimizing the training regimen depending on neuromuscular fatigue is crucial for the well-being of professionals intensively practicing motor skills, such as athletes and musicians, as persistent fatigue can hinder learning and cause neuromuscular injuries. However, accurate assessment of fatigue is challenging because of the dissociation between subjective perception and its impact on motor and cognitive performance. To address this issue, we investigated the interplay between fatigue and learning development in 28 pianists during three hours of auditory-motor training, dividing them into two groups subjected to different resting conditions. Changes in behavior and muscle activity during training were measured to identify potential indicators capable of detecting fatigue before subjective awareness. Our results indicate that motor learning and fatigue development are independent of resting frequency and timing. Learning indices, such as reduction in force and timing errors throughout training, did not differ between the groups. No discernible distinctions emerged in fatigue-related behavioral and physiological indicators between the groups. Regression analysis revealed that several fatigue-related indicators, such as tapping speed variability and electromyogram amplitude per unit force, could explain the learning of timing and force control. Our findings suggest the absence of a universal resting schedule for optimizing auditory-motor learning.

Analysis and Clustering of Upper Limb Motion during the Hand Dexterity Pegboard Test using Inertial Sensor Systems

Maintaining hand and upper limb mobility is important from the viewpoint of freedom in daily life and high performance in work. Few studies on the mobility and dexterity of the upper limb have focused on detailed hand and finger movements. Therefore, we measured the motion of the upper limbs during a general hand dexterity pegboard test using inertial sensor systems and our previous measuring method. To clarify the characteristics of each purpose of motion, we divided the peg-in-hole motion in the pegboard test into its three sections, focusing on two sections: the pinch section, and the carry and insert section. In addition, the obtained joint angles were grouped into arm group and finger group, and singular value decomposition was performed for each joint group in each section. By clustering the decomposition results across five subjects' multiple right and left arm tests, and averaging the singular vectors in the same cluster, the joint distributions and combinations could be clarified. In addition, by recalculating joint angles from averaged SVD results and applying them to the rigid link model, we obtained motion animation with characteristics that made it possible to more clearly understand the requirements for greater dexterity. These results suggested high dexterity motion characteristics in the pinch section, and the carry and insert section of the pegboard test.

Higher synchronization stability with piano experience: relationship with finger and presentation modality

BACKGROUND

Synchronous finger tapping to external sensory stimuli is more stable for audiovisual combined stimuli than sole auditory or visual stimuli. In addition, piano players are superior in synchronous tapping and manipulating the ring and little fingers as compared to inexperienced individuals. However, it is currently unknown whether the ability to synchronize to external sensory stimuli with the ring finger is at the level of the index finger in piano players. The aim of this study was to compare the effect of piano experience on synchronization stability between the index and ring fingers using auditory, visual, and audiovisual combined stimuli.

METHODS

Thirteen piano players and thirteen novices participated in this study. They were instructed to tap with their index or ring finger synchronously to auditory, visual, and audiovisual combined stimuli. The stimuli were presented from an electronic metronome at 1 Hz, and the tapping was performed 30 times in each condition. We analyzed standard deviation of intervals between the stimulus onset and the tap onset as synchronization stability.

RESULTS

Synchronization stability for visual stimuli was lower during ring than index finger tapping in novices; however, this decline was absent in piano players. Also, piano players showed the higher synchronization stability for audiovisual combined stimuli than sole visual and auditory stimuli when tapping with the index finger. On the other hand, in novices, synchronization stability was higher for audiovisual combined stimuli than only visual stimuli.

CONCLUSIONS

These findings suggest that improvements of both sensorimotor processing and finger motor control by piano practice would contribute to superior synchronization stability.

How the hand has shaped sign languages

In natural languages, biological constraints push toward cross-linguistic homogeneity while linguistic, cultural, and historical processes promote language diversification. Here, we investigated the effects of these opposing forces on the fingers and thumb configurations (handshapes) used in natural sign languages. We analyzed over 38,000 handshapes from 33 languages. In all languages, the handshape exhibited the same form of adaptation to biological constraints found in tasks for which the hand has naturally evolved (e.g., grasping). These results were not replicated in fingerspelling—another task where the handshape is used—thus revealing a signing-specific adaptation. We also showed that the handshape varies cross-linguistically under the effects of linguistic, cultural, and historical processes. Their effects could thus emerge even without departing from the demands of biological constraints. Handshape’s cross-linguistic variability consists in changes in the frequencies with which the most faithful handshapes to biological constraints appear in individual sign languages.

Back to feedback: aberrant sensorimotor control in music performance under pressure

Precisely timed production of dexterous actions is often destabilized in anxiogenic situations. Previous studies demonstrated that cognitive functions such as attention and working memory as well as autonomic nervous functions are susceptible to psychological stress in skillful performance while playing sports or musical instruments. However, it is not known whether the degradation of sensorimotor functions underlies such a compromise of skillful performance due to psychophysiological distress. Here, we addressed this issue through a set of behavioral experiments. After artificially delaying the timing of tone production while playing the piano, the local tempo was abnormally disrupted only under pressure. The results suggest that psychological stress degraded the temporal stability of movement control due to an abnormal increase in feedback gain. A learning experiment further demonstrated that the temporal instability of auditory-motor control under pressure was alleviated after practicing piano while ignoring delayed auditory feedback but not after practicing while compensating for the delayed feedback. Together, these findings suggest an abnormal transition from feedforward to feedback control in expert piano performance with psychological stress, which can be mitigated through specialized sensorimotor training that involves piano practice while volitionally ignoring the artificially delayed provision of auditory feedback.

In order to establish if the degradation of sensorimotor functions underlies the stress-associated disruption of skilful performance, Furuya et al examined participants undergoing a piano playing task under stress. Their data suggests the occurrence of a stress-induced transition from feedforward to feedback control, which can be mitigated through sensorimotor training involving piano practice while volitionally ignoring the artificially delayed provision of auditory feedback.

Analysis of Dexterity Motion by Singular Value Decomposition for Hand Movement Measured Using Inertial Sensors

Finger movements play an important role in many daily human actions. Among the studies on the dexterity of fingers required for various tasks in neurology and simple evaluation tests, few have focused on detailed finger movements themselves. Therefore, in this study, we improved the hand motion measurement system using inertial sensors and the motion analysis method developed in our previous study and measured the motion of the upper limbs (including the fingers) during a general finger dexterity test. By applying singular value decomposition to the obtained joint angles and decomposing them into simpler movement units, we obtained the timing of each movement unit and the purpose of each movement as the coordination state of the joints. By applying hierarchical clustering to multiple trials in a finger dexterity test, we also determined the similarity between trials and investigated the characteristics of movements with higher dexterity. We investigated the motor characteristics in finger dexterity by analyzing our results.

Adaptation of the Corticomuscular and Biomechanical Systems of Pianists

Independent control of movements between the fingers plays a role in hand dexterity characterizing skilled individuals. However, it remains unknown whether and in what manner neuromuscular and biomechanical constraints on the movement independence of the fingers depend on motor expertise. Here, we compared motor dexterity, corticospinal excitability of multiple muscles, muscular activation, and anatomical features of the fingers between the pianists and nonpianists. When the ring finger was passively moved by a robot, passive motions produced at the adjacent fingers were smaller for the pianists than the nonpianists, indicating reduced biomechanical constraint of fingers in the pianists. In contrast, when the ring finger moved actively, we found no group difference in passive motions produced at the adjacent fingers; however, reduced inhibition of corticospinal excitability of the adjacent fingers in the pianists compared with the nonpianists. This suggests strengthened neuromuscular coupling between the fingers of the pianists, enhancing the production of coordinated finger movements. These group differences were not evident during the index and little finger movements. Together, pianists show expertise-dependent biomechanical and neurophysiological adaptations, specifically at the finger with innately low movement independence. Such contrasting adaptations of pianists may subserve dexterous control of both the individuated and coordinated finger movements.

Factors of choking under pressure in musicians

Under pressure, motor actions, such as those required in public speech, surgery, or musical performance, can be compromised, even when these have been well-trained. The latter is often referred to as 'choking' under pressure. Although multifaceted problems mediate such performance failure in anxiogenic situations, such as compromised motor dexterity and cognitive disruption, the fundamental set of abnormalities characterizing choking under pressure and how these abnormalities are related have not been elucidated. Here, we attempted, first, to classify behavioural, psychological, and physiological abnormalities associated with choking under pressure in musicians and, second, to identify their relationship based on datasets derived from a questionnaire with 258 pianist respondents. Explorative factor analysis demonstrated eight functional abnormalities related to the musicians' choking, such as attention to the audience, erroneous motor actions, perceptual confusion, and failure of memory recall, which however did not include exaggerated attention to the performance. This suggests distraction of attention away from skill execution, which may underlie the spoiled performance under pressure. A structural equation analysis further inferred causal relationships among them. For instance, while failure of memory recall was influenced by passive behaviours manifesting under pressure, erroneous motor actions during performance were influenced by feeling rushed and a loss of body control. In addition, some specific personal traits, such as neuroticism, public self-consciousness, and a lack of confidence, were associated with the extent to which pressure brought about these abnormalities. These findings suggest that distinct psycho-behavioural abnormalities and personal traits underlie the detrimental effects of pressure on musical performance.

What is the significance of the traditional pinching mode of holding chopsticks?

Background

The purpose of this study was to clarify the influence of manipulation mode of chopsticks on the learning process, using assessment of task performance and electromyography, and to understand the significance of the traditional manipulation mode from the viewpoint of physiological anthropology. Previous studies have described two modes of manipulating chopsticks, the traditional pincers-pinching mode and the scissors-pinching mode.

Methods

We conducted experiments with two conditions of holding chopsticks: scissors mode and pincers mode. Eight subjects participated and were assigned to these modes, and they learned handling tasks in their assigned mode for 5 days with the non-dominant hand. We measured task execution times and conducted electromyography of the following muscles: first dorsalis interosseus, flexor pollicis brevis, flexor digiti minimi brevis, flexor digitorum superficialis, and extensor digitorum.

Results

The training effects were found in each mode. The pincers mode showed significantly shorter task performance times than did scissors mode. On electromyography, significant increases in activity of flexor digiti minimi brevis and tended an increase in flexor digitorum superficialis and a decrease in extensor digitorum occurred in pincers mode but not in scissors mode.

Conclusions

The traditional mode of holding chopsticks was associated with not only high task performance but also an advantage in terms of learning motor control.