Clara Ziane

Neural oscillations synchronize with rhythmic stimuli, shaping perception and action. Auditory-motor synchronization (AMS) enhances this process but most evidence comes from finger tapping, an attentionally demanding voluntary behaviour. Whether motor-driven modulation of neural synchronization generalizes to more automatic movements like walking remains unclear. In this study, we used mobile EEG to compare neural synchronization to auditory rhythms during tapping and walking in 40 older male and female participants, manipulating cognitive load (single vs . dual task) and task instructions (synchronize with vs . ignore metronome). EEG components attuned to metronome frequencies were extracted and complementary measures of neural synchronization were computed (phase coupling to the stimulus, power at the stimulus frequency, and the stability of instantaneous frequencies). Both movements enhanced neural synchronization relative to passive listening. Neural synchronization was further increased by instructions to synchronize, but only during tapping. This instruction-facilitating effect was lost in dual tasks. These findings suggest that AMS recruits movement-dependent neural and cognitive mechanisms, depending on where AMS lies on a continuum from voluntary-controlled to automatic forms of coordination, with implications for rhythm-based interventions in aging. Significance statement: Neural coupling to stimuli in the environment shape perception and action, but its dependence on movement type and cognitive control is poorly understood. Using mobile EEG, we show that both finger tapping and walking enhance neural coupling to the auditory stimuli, but tapping is uniquely modulated by task factors. Our findings suggest that cortical involvement during rhythmic motor tasks differs for voluntary (tapping) and automatic (walking) behaviours. As gait can move from being mostly automatic to voluntary-controlled ( e.g. , under heightened cognitive load, in motor disorders), it offers a unique opportunity to study the dynamic interactions between sensory, motor, and cognitive processes supporting neural coupling to auditory stimuli.

Synchronizing movements to rhythmic auditory stimuli, like metronome cues, is a core human ability that can give insight into typical and atypical functioning. Often, this ability is measured through finger-tapping tasks. Although models of beat synchronization predict similar temporal performance across motor effectors, experimental evidence is conflicted regarding the existence of a generalized rhythm system governing all motor behaviours. Thus, our goal was to determine whether timing mechanisms in healthy individuals are effector-dependent or independent. To this aim, we tested to what extent finger tapping and walking were affected by manipulating cognitive load and instructions in forty older adults. Tapping variability increased under high cognitive load and decreased with instructions to synchronize, while gait remained highly stable across tasks. These results support effector-dependent timing mechanisms. Interestingly, synchronization consistency was negatively impacted by cognitive load across both movements. Finally, there was no cross-effector correlation for motor variability or synchronization performance, except when cognitive load was the highest. These findings point towards partly effector-dependent mechanisms. We propose that shared mechanisms emerge when gait shifts towards voluntary control, such as under high cognitive load. This finding is supported by studies on clinical populations, in which patients exhibit voluntary control of gait.

Synchronization of movements to auditory rhythmic cues, such as music or metronomes, often occurs spontaneously. Nonetheless, important inter-individual differences exist in auditory-motor synchronization (AMS) performance. Effects of rhythm on movements are partly modulated by rhythmic abilities, which include beat perception, motor production, and sensorimotor integration. These rhythmic abilities are often assessed using finger tapping tasks, which can be performed in highly controlled environments and are easy to implement. In this article, we present limitations associated with finger-tapping tasks and propose gait as a superior model for investigating and training rhythmic abilities. We focus on three key elements that differentiate gait from tapping, and which are critical in assessing AMS: the need to coordinate multiple effectors, emergent timing associated with continuous actions, and movement automaticity. Interestingly, cued-gait interventions (i.e., walking to rhythmic auditory cues for several weeks) have shown positive effects on all aspects of rhythmic abilities, while tapping interventions might lead to more limited transfer. In sum, gait offers a functionally rich behavioural model that can capture the complexity and ecological validity necessary to study and train AMS.

Synchronization of movements to auditory rhythmic cues, such as music or metronomes, often occurs spontaneously. Nonetheless, important interindividual differences exist in auditory–motor synchronization (AMS). Effects of rhythm on movements are partly modulated by rhythmic abilities, which include beat perception, motor production, and sensorimotor integration. These rhythmic abilities are often assessed using finger‐tapping tasks, which can be performed in highly controlled environments and are easy to implement. In this article, we present limitations associated with finger‐tapping tasks and propose gait as an alternative model for investigating and training rhythmic abilities. We focus on three key elements that differentiate gait from tapping and are critical in assessing AMS: the need to coordinate multiple effectors, emergent timing associated with continuous actions, and movement automaticity. Interestingly, cued–gait interventions (i.e., walking to rhythmic auditory cues for several weeks) have shown positive effects on all aspects of rhythmic abilities, while tapping interventions (e.g., playing tablet‐based serious games) might lead to more limited transfer. In sum, gait offers a functionally rich behavioral model that can capture the complexity and ecological validity necessary to study and train AMS.

Muscle fatigue is a primary risk factor in developing musculoskeletal disorders, which affect up to 93% musicians, especially violinists. Devices providing dynamic assistive support (DAS) to the violin-holding arm can lessen fatigue. The objective was to assess DAS effects on electromyography median frequency and joint kinematics during a fatiguing violin-playing task. Fifteen university-level and professional violinists were equipped with electromyography sensors and reflective markers to record upper-body muscle activity and kinematics. They played G scales with and without DAS until exhaustion. Paired t-tests assessed DAS effects on delta (final-initial) electromyography median frequencies and joint kinematics. DAS prevented the median frequency decrease of left supraspinatus, superior trapezius, and right medial deltoid, and increases in trunk rotation, left-wrist abduction, and right arm-elevation plane. DAS effects on kinematics were marginal due to retention of musical performance despite fatigue. However, DAS reduced fatigue of several muscles, which is promising for injury prevention.Practitioner summary: Violinists are greatly affected by musculoskeletal disorders. Effects of a mobility assistive device on muscle fatigue during violin playing was investigated. The assistive technology slowed down the development of fatigue for three neck/shoulder muscles, making assisted musical performance a promising avenue to prevent violinists' injuries.

About 70% of children and adolescents with cerebral palsy experience gait impairments which affect their autonomy and well-being. Robotic-assisted gait training using the Lokomat is particularly promising for rehabilitation as it provides a standardized environment favoring the massive repetition of the movement, in which physical demands are low on the therapist and high training loads can be achieved. As no guidelines exist regarding training protocols and Lokomat settings, the goal of this narrative review was to summarize previously published information on the use of RAGT in children and adolescents with cerebral palsy and to provide an opinion on possibilities for improving future research. The thirteen studies reviewed reported both positive and null effects of Lokomat training on gait. Half of the studies combined the Lokomat with other types of training, and only five used a control intervention to assess its benefit. Overall, training was administered 1–5 times per week for 20–60 min, over 1–12 weeks. Although Lokomat settings were not always described, progressively decreasing body weight support and guidance while increasing the treadmill speed appeared to be prioritized. The variety of training protocols and settings used did not allow pooling of the studies to assess the effects of interventions on gait parameters in children and adolescents with cerebral palsy. This narrative review highlights the need for homogenization of interventions so that clear guidelines can emerge and be applied in rehabilitation centers.

About 70% of children and adolescents with cerebral palsy experience gait impairments which affect their autonomy and well-being. Robotic-assisted gait training using the Lokomat is particu-larly promising for rehabilitation as it provides a standardized environment favoring the massive repetition of the movement, in which physical demands are low on the therapist and high training loads can be achieved. As no guidelines exist regarding training protocols and Lokomat settings, the goal of this study was to review the literature on Lokomat-assisted gait therapy and possibly make training recommendations. The twelve studies reviewed reported both positive and null effects of Lokomat training on gait. Half of the studies combined Lokomat with other types of training and only five used a control intervention to assess its benefit. Overall, training was administered 1-5 times per week for 20-60 minutes, over 1-12 weeks. Although Lokomat settings were not always described, progressively decreasing body-weight support and guidance, while increasing treadmill speed appear to be prioritized. The variety of training protocols and settings used did not allow pooling of the studies to assess effects of interventions on gait parameters in children and adoles-cents with cerebral palsy. This review highlights the need for homogenization of interventions so that clear guidelines can emerge and be applied in rehabilitation centers.

Assessing violinists’ motor and musical performance adaptations to dynamic assistive support (DAS) provided by a passive device, using a force-field adaptation paradigm. Up to 93% of instrumentalists are affected by musculoskeletal injuries and particularly violinists. The repetitive nature of their work may lead to muscle fatigue, an injury risk factor. DAS has been used in occupational settings to minimize muscle activations and limit fatigue accumulation. DAS may however affect motor and musical performance. Fifteen expert violinists were equipped with reflective markers and surface and intramuscular electromyography (EMG) sensors. Movements, muscle activations, and sound were recorded while participants completed three experimental conditions for which they continuously played a 13-s musical excerpt: Control (no DAS), Adaptation (DAS), and Washout (no DAS). DAS was applied at the left elbow (violin-holding side). Conditions were repeated 1 week later. Participants later listened to their own audio recordings playing with and without DAS and blindly assessed their performances. Linear mixed models were used to compare DAS and no-DAS conditions’ kinematic, EMG, and musical performance data. DAS perturbed user kinematics but reduced mean activations of left medial deltoid and superior trapezius. Joint kinematic and muscle activation patterns between DAS and no DAS conditions however remained similar. Musical performance was unchanged with DAS. Though DAS modified violinists’ upper-limb configurations, resulting kinematics were not detrimental to musical performance. Reduced muscle activations with DAS could contribute to lessening muscle fatigue. Although its effect on muscle fatigue should be further investigated, DAS might be useful in preventing violinists’ injuries.