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We report an experiment that tested the vestibular syncopation rhythm hypothesis, which holds that the rhythmic effect of syncopation is a form of vestibular reflexive/automated response to a postural perturbation, for example during locomotion. Electrophysiological signals were recorded from the cerebral cortex and cerebellum during processing of rhythmic sequences in a sample of experienced participants. Recordings were made using four different stimulus modalities, auditory, axial, vestibular and visual, under different rhythmic timing conditions, irregular, regular and syncopated/uncertain. Brain current activity was measured using a 10 dipole source regions of interest model in each of the participants, each modality, each timing condition, and for each beat within the bar of the rhythm. The cross-modal spectral power in frontal EEG and cerebellar ECeG was also analysed. The results show that the brain activity increases from the irregular to the regular and then from the regular to the uncertain timing conditions. However, the vestibular modality induces the greatest total brain activity across the regions of interest, and exhibits the highest sensitivity to the interaction of beat structure with the timing conditions in both source currents and spectral power. These data provide further evidence to support the primal role of the vestibular system in rhythm perception.

Developments in cognitive neuroscience have led to the emergence of hyperscanning, the simultaneous measurement of brain activity from multiple people. Hyperscanning holds promise for the study of social cognition, including joint action, because of its potential to capture neural processes that occur within and between people as they coordinate actions toward a shared goal. Skeptical voices have, however, questioned the utility of hyperscanning based on concerns regarding interpretability of inter-brain measures and lack of a unifying theoretical approach. Here, we provide a practical guide for researchers considering using hyperscanning to study joint action and seeking to mitigate these concerns. We focus specifically on EEG hyperscanning, which is widely available and optimally suited for capturing fine-grained temporal dynamics of action coordination. Our guidelines cover questions that are likely to arise when planning a hyperscanning project, ranging from whether hyperscanning is appropriate for answering one’s research questions to considerations for study design, dependent variable selection, data analysis, and visualization. Our perspective is that benefits of hyperscanning can be maximized, and interpretability issues mitigated, if joint action researchers follow clear guidelines – including those provided here – to carefully consider the theoretical implications of their research design choices and other methodological decisions.

Periodicity is a fundamental property of biological systems, including human movement systems. Periodic movements support displacements of the body in the environment as well as interactions and communication between individuals. Here, we use electroencephalography (EEG) to investigate the neural tracking of visual periodic motion, and more specifically, the relevance of spatiotemporal information contained at and between their turning points. We compared EEG responses to visual sinusoidal oscillations versus nonlinear Rayleigh oscillations, which are both typical of human movements. These oscillations contain the same spatiotemporal information at their turning points but differ between turning points, with Rayleigh oscillations having an earlier peak velocity, shown to increase an individual's capacity to produce accurately synchronized movements. EEG analyses highlighted the relevance of spatiotemporal information between the turning points by showing that the brain precisely tracks subtle differences in velocity profiles, as indicated by earlier EEG responses for Rayleigh oscillations. The results suggest that the brain is particularly responsive to velocity peaks in visual periodic motion, supporting their role in conveying behaviorally relevant timing information at a neurophysiological level. The results also suggest key functions of neural oscillations in the Alpha and Beta frequency bands, particularly in the right hemisphere. Together, these findings provide insights into the neural mechanisms underpinning the processing of visual periodic motion and the critical role of velocity peaks in enabling proficient visuomotor synchronization.

When we listen to music, we often feel the urge to tap our fingers, stomp our feet, or move our bodies. This pleasurable sensation of wanting to move one's body with the music has been termed "groove." Research on groove was initially conducted mainly in the fields of musicology, ethnomusicology and philosophy, and in the 2000s, researchers within the field of empirical psychology began to investigate the concept of groove and the characteristics of music associated with it. In the 2010s, studies of the relationship between groove and underlying brain structures and functional processes emerged and the topic has recently become a prominent theme in empirical research on musical behavior. This review aims to provide a comprehensive characterization of groove and to highlight future directions for related empirical research. In doing so, we focus on two topics that have the potential to provide new insights into perception and action from the perspectives of psychology and neuroscience: (1) sensorimotor interactions and (2) the role of the motor system in predictive processing. To this end, we survey the literature on groove conducted in the fields of psychology and neuroscience from 2006 to 2022 in five sections: (1) the concept of groove, (2) musical features related to groove, (3) responses to groove including body movement and neurophysiological activity, (4) characteristics of listeners that influence the experience of groove, and (5) the effect of culture and environment on groove perception. Through the review, we propose four themes as promising future directions for empirical study: (1) social aspects of groove, (2) the effect of microtiming and syncopation on groove, (3) the mechanisms by which groove is evoked, and (4) clinical implications and applications of groove. Taken together, these research efforts may ultimately lead to an increased understanding of human sociality, evolution, and the brain and mind.

We report the results of an experiment in which electrophysiological activity was recorded from the human cerebellum and cerebrum in a sample of 14 healthy subjects before, during and after a classical eye blink conditioning procedure with an auditory tone as conditional stimulus and a maxillary nerve unconditional stimulus. The primary aim was to show changes in the cerebellum and cerebrum correlated with behavioral ocular responses. Electrodes recorded EMG and EOG at peri-ocular sites, EEG from over the frontal eye-fields and the electrocerebellogram (ECeG) from over the posterior fossa. Of the 14 subjects half strongly conditioned while the other half were resistant. We confirmed that conditionability was linked under our conditions to the personality dimension of extraversion-introversion. Inhibition of cerebellar activity was shown prior to the conditioned response, as predicted by Albus (1971). However, pausing in high frequency ECeG and the appearance of a contingent negative variation (CNV) in both central leads occurred in all subjects. These led us to conclude that while conditioned cerebellar pausing may be necessary, it is not sufficient alone to produce overt behavioral conditioning, implying the existence of another central mechanism. The outcomes of this experiment indicate the potential value of the noninvasive electrophysiology of the cerebellum.

Joint music performance requires flexible sensorimotor coordination between self and other. Cognitive and sensory parameters of joint action—such as shared knowledge or temporal (a)synchrony—influence this coordination by shifting the balance between self-other segregation and integration. To investigate the neural bases of these parameters and their interaction during joint action, we asked pianists to play on an MR-compatible piano, in duet with a partner outside of the scanner room. Motor knowledge of the partner’s musical part and the temporal compatibility of the partner’s action feedback were manipulated. First, we found stronger activity and functional connectivity within cortico-cerebellar audio-motor networks when pianists had practiced their partner’s part before. This indicates that they simulated and anticipated the auditory feedback of the partner by virtue of an internal model. Second, we observed stronger cerebellar activity and reduced behavioral adaptation when pianists encountered subtle asynchronies between these model-based anticipations and the perceived sensory outcome of (familiar) partner actions, indicating a shift towards self-other segregation. These combined findings demonstrate that cortico-cerebellar audio-motor networks link motor knowledge and other-produced sounds depending on cognitive and sensory factors of the joint performance, and play a crucial role in balancing self-other integration and segregation.

Human communication entails subtle non-verbal modes of expression, which can be analyzed quantitatively using computational approaches and thus support human sciences. In this paper we present huSync, a computational framework and system that utilizes trajectory information extracted using pose estimation algorithms from video sequences to quantify synchronization between individuals in small groups. The system is exploited to study interpersonal coordination in musical ensembles. Musicians communicate with each other through sounds and gestures, providing nonverbal cues that regulate interpersonal coordination. huSync was applied to recordings of concert performances by a professional instrumental ensemble playing two musical pieces. We examined effects of different aspects of musical structure (texture and phrase position) on interpersonal synchronization, which was quantified by computing phase locking values of head motion for all possible within-group pairs. Results indicate that interpersonal coupling was stronger for polyphonic textures (ambiguous leadership) than homophonic textures (clear melodic leader), and this difference was greater in early portions of phrases than endings (where coordination demands are highest). Results were cross-validated against an analysis of audio features, showing links between phase locking values and event density. This research produced a system, huSync, that can quantify synchronization in small groups and is sensitive to dynamic modulations of interpersonal coupling related to ambiguity in leadership and coordination demands, in standard video recordings of naturalistic human group interaction. huSync enabled a better understanding of the relationship between interpersonal coupling and musical structure, thus enhancing collaborations between human and computer scientists.

Rhythmic patterns in interactive contexts characterize human behaviours such as conversational turn-taking. These timed patterns are also present in other animals, and often described as rhythm. Understanding fine-grained temporal adjustments in interaction requires complementary quantitative methodologies. Here, we showcase how vocal interactive rhythmicity in a non-human animal can be quantified using a multi-method approach. We record vocal interactions in harbour seal pups ( Phoca vitulina ) under controlled conditions. We analyse these data by combining analytical approaches, namely categorical rhythm analysis, circular statistics and time series analyses. We test whether pups' vocal rhythmicity varies across behavioural contexts depending on the absence or presence of a calling partner. Four research questions illustrate which analytical approaches are complementary versus orthogonal. For our data, circular statistics and categorical rhythms suggest that a calling partner affects a pup's call timing. Granger causality suggests that pups predictively adjust their call timing when interacting with a real partner. Lastly, the ADaptation and Anticipation Model estimates statistical parameters for a potential mechanism of temporal adaptation and anticipation. Our analytical complementary approach constitutes a proof of concept; it shows feasibility in applying typically unrelated techniques to seals to quantify vocal rhythmic interactivity across behavioural contexts. This article is part of a discussion meeting issue ‘Face2face: advancing the science of social interaction’.

Music listening often entails spontaneous perception and body movement to a periodic pulse-like meter. There is increasing evidence that this cross-cultural ability relates to neural processes that selectively enhance metric periodicities, even when these periodicities are not prominent in the acoustic stimulus. However, whether these neural processes emerge early in development remains largely unknown. Here, we recorded the electroencephalogram (EEG) of 20 healthy 5- to 6-month-old infants, while they were exposed to two rhythms known to induce the perception of meter consistently across Western adults. One rhythm contained prominent acoustic periodicities corresponding to the meter, whereas the other rhythm did not. Infants showed significantly enhanced representations of meter periodicities in their EEG responses to both rhythms. This effect is unlikely to reflect the tracking of salient acoustic features in the stimulus, as it was observed irrespective of the prominence of meter periodicities in the audio signals. Moreover, as previously observed in adults, the neural enhancement of meter was greater when the rhythm was delivered by low-pitched sounds. Together, these findings indicate that the endogenous enhancement of metric periodicities beyond low-level acoustic features is a neural property that is already present soon after birth. These high-level neural processes could set the stage for internal representations of musical meter that are critical for human movement coordination during rhythmic musical behavior. Research Highlights: 5- to 6-month-old infants were presented with auditory rhythms that induce the perception of a periodic pulse-like meter in adults. Infants showed selective enhancement of EEG activity at meter-related frequencies irrespective of the prominence of these frequencies in the stimulus. Responses at meter-related frequencies were boosted when the rhythm was conveyed by bass sounds. High-level neural processes that transform rhythmic auditory stimuli into internal meter templates emerge early after birth.

When people interact with each other, their brains synchronize. However, it remains unclear whether interbrain synchrony (IBS) is functionally relevant for social interaction or stems from exposure of individual brains to identical sensorimotor information. To disentangle these views, the current dual-EEG study investigated amplitude-based IBS in pianists jointly performing duets containing a silent pause followed by a tempo change. First, we manipulated the similarity of the anticipated tempo change and measured IBS during the pause, hence, capturing the alignment of purely endogenous, temporal plans without sound or movement. Notably, right posterior gamma IBS was higher when partners planned similar tempi, it predicted whether partners’ tempi matched after the pause, and it was modulated only in real, not in surrogate pairs. Second, we manipulated the familiarity with the partner’s actions and measured IBS during joint performance with sound. Although sensorimotor information was similar across conditions, gamma IBS was higher when partners were unfamiliar with each other’s part and had to attend more closely to the sound of the performance. These combined findings demonstrate that IBS is not merely an epiphenomenon of shared sensorimotor information but can also hinge on endogenous, cognitive processes crucial for behavioral synchrony and successful social interaction.

Complex sequential behaviors, such as speaking or playing music, entail flexible rule-based chaining of single acts. However, it remains unclear how the brain translates abstract structural rules into movements. We combined music production with multimodal neuroimaging to dissociate high-level structural and low-level motor planning. Pianists played novel musical chord sequences on a muted MR-compatible piano by imitating a model hand on screen. Chord sequences were manipulated in terms of musical harmony and context length to assess structural planning, and in terms of fingers used for playing to assess motor planning. A model of probabilistic sequence processing confirmed temporally extended dependencies between chords, as opposed to local dependencies between movements. Violations of structural plans activated the left inferior frontal and middle temporal gyrus, and the fractional anisotropy of the ventral pathway connecting these two regions positively predicted behavioral measures of structural planning. A bilateral frontoparietal network was instead activated by violations of motor plans. Both structural and motor networks converged in lateral prefrontal cortex, with anterior regions contributing to musical structure building, and posterior areas to movement planning. These results establish a promising approach to study sequence production at different levels of action representation.

We report an experiment to investigate possible vestibular effects on finger tapping to an auditory anapaest rhythm. In a sample of 10 subjects, index finger acceleration and tapping force were recorded along with extensor/flexor activity and the associated electroencephalographic activity measured at central and cerebellar surface electrodes. In a prior session with a standard short air-conducted 500-Hz pip, vestibular evoked myogenic potential thresholds were measured and subsequently used to set the acoustic intensity. During the main experiment subjects were asked to synchronise tapping to the pips arranged in the anapaest at two different frequencies, 500 Hz vs 5 kHz, so that only the low-frequency high-intensity condition was a vestibular, as well as an auditory stimulus. We hypothesised that a vestibular effect would manifest in an interaction between the frequency and intensity factors for a range of dependent measures of tapping performance. No clear evidence was found for vestibular effects, but this was likely due to the confounding effects of an independent effect of intensity and the relative weakness of the acoustic vestibular stimulus. However, the data did show novel evidence for two distinct timing processes for the flexion and extension stages of a tap cycle and two distinct timing strategies, which we refer to as ‘staccato’ and ‘legato’, characterised by different profiles of force and extension.

Human interaction often requires the precise yet flexible interpersonal coordination of rhythmic behavior, as in group music making. The present fMRI study investigates the functional brain networks that may facilitate such behavior by enabling temporal adaptation (error correction), prediction, and the monitoring and integration of information about ‘self’ and the external environment. Participants were required to synchronize finger taps with computer-controlled auditory sequences that were presented either at a globally steady tempo with local adaptations to the participants' tap timing (Virtual Partner task) or with gradual tempo accelerations and decelerations but without adaptation (Tempo Change task). Connectome-based predictive modelling was used to examine patterns of brain functional connectivity related to individual differences in behavioral performance and parameter estimates from the adaptation and anticipation model (ADAM) of sensorimotor synchronization for these two tasks under conditions of varying cognitive load. Results revealed distinct but overlapping brain networks associated with ADAM-derived estimates of temporal adaptation, anticipation, and the integration of self-controlled and externally controlled processes across task conditions. The partial overlap between ADAM networks suggests common hub regions that modulate functional connectivity within and between the brain's resting-state networks and additional sensory-motor regions and subcortical structures in a manner reflecting coordination skill. Such network reconfiguration might facilitate sensorimotor synchronization by enabling shifts in focus on internal and external information, and, in social contexts requiring interpersonal coordination, variations in the degree of simultaneous integration and segregation of these information sources in internal models that support self, other, and joint action planning and prediction.

During joint action, the sense of agency enables interaction partners to implement corrective and adaptive behaviour in response to performance errors. When agency becomes ambiguous (e.g. when action similarity encourages perceptual self–other overlap), confusion as to who produced what may disrupt this process. The current experiment investigated how ambiguity of agency affects behavioural and neural responses to errors in a joint action domain where self–other overlap is common: musical duos. Pairs of pianists performed piano pieces in synchrony, playing either the same pitches (ambiguous agency) or different pitches (unambiguous agency) while electroencephalography (EEG) was recorded for each individual. Behavioural and event-related potential results showed no effects of the agency manipulation but revealed differences in how distinct error types are processed. Self-produced ‘wrong note’ errors (substitutions) were left uncorrected, showed post-error slowing and elicited an error-related negativity (ERN) peaking before erroneous keystrokes (pre-ERN). In contrast, self-produced ‘extra note’ errors (additions) exhibited pre-error slowing, error and post-error speeding, were rapidly corrected and elicited the ERN. Other-produced errors evoked a feedback-related negativity but no behavioural effects. Overall findings shed light upon how the nervous system supports fluent interpersonal coordination in real-time joint action by employing distinct mechanisms to manage different types of errors.

Investigating cues that underpin perceptual judgments of interpersonal coordination has important implications for understanding sociocognitive evaluations of the quality of human interactions. With a focus on musical interpersonal coordination, we conducted 2 experiments investigating the impact of music style, modality of stimulus presentation, rater expertise, and audio/visual stimulus features on ratings of perceived synchrony in improvised duo performances. In the first experiment, participants made synchrony ratings following 10-s excerpts of musical performances, whereas in the second experiment, participants rated longer (up to 1 min) excerpts continuously as the music unfolded. Several consistent results emerged across the 2 experiments, including that participants perceived standard jazz improvisations featuring a regular beat as significantly more synchronous than free improvisations that aimed to eschew the induction of such a beat. However, ratings of perceived synchrony were more similar across these 2 styles when only the visual information from the performance was available, suggesting that performers’ bodily cues functioned similarly to communicate and coordinate musical intentions. Computational analysis of the audio and visual aspects of the performances indicated that synchrony ratings increased with increases in audio event density and when coperformers engaged in periodic movements at similar frequencies, whereas the salience of visual information increased when synchrony ratings were made continuously over longer timescales. These studies reveal new insights about the correspondence between objective and subjective measures of synchrony and contribute methodological advances indicating both parallels and divergences between the results obtained in paradigms utilizing global versus continuous ratings of musical synchrony

Humans have a natural tendency to move to music, which has been linked to the tight coupling between the auditory and motor system and the active role of the motor system in the perception of musical rhythms. High-groove music is particularly successful at inducing spontaneous movement, due to the engagement of (motor) prediction processes. However, how music listening transfers to the muscles even when no movement is intended is less known. Here we used cortico-muscular coherence (CMC) to investigate changes along the cortico-muscular pathway in response to different levels of groove in music listening without intention to move. Electroencephalography (EEG), Electromyography (EMG) from the finger and foot flexors, and continuous force signals were recorded in 18 participants while listening to either high-groove music, low-groove music or silence. Participants were required to hold a steady isometric contraction during all listening conditions. Subjective ratings confirmed that different levels of groove were successfully induced. However, no evidence was found for an effect of music, even high-groove music, on participants' CMC and ability to maintain a steady force for both upper and lower limbs irrespective of musical expertise. These results thus do not support a top-down influence of groove on cortico-muscular coupling. Nevertheless, it remains possible that such influence might occur in the form of dynamic modulations and/or with more active listening. Therefore, these results encourage further research to better understand the effects of groove on the motor system.

Supplementary Information: The online version contains supplementary material available at https://doi.org/ 10.1038/s41598-022-10342-5, Human movements are spontaneously attracted to auditory rhythms, triggering an automatic activation of the motor system, a central phenomenon to music perception and production. Cortico- muscular coherence (CMC) in the theta, alpha, beta and gamma frequencies has been used as an index of the synchronisation between cortical motor regions and the muscles. Here we investigated how learning to produce a bimanual rhythmic pattern composed of low- and high-pitch sounds affects CMC in the beta frequency band. Electroencephalography (EEG) and electromyography (EMG) from the left and right First Dorsal Interosseus and Flexor Digitorum Superficialis muscles were concurrently recorded during constant pressure on a force sensor held between the thumb and index finger while listening to the rhythmic pattern before and after a bimanual training session. During the training, participants learnt to produce the rhythmic pattern guided by visual cues by pressing the force sensors with their left or right hand to produce the low- and high-pitch sounds, respectively. Results revealed no changes after training in overall beta CMC or beta oscillation amplitude, nor in the correlation between the left and right sides for EEG and EMG separately. However, correlation analyses indicated that left- and right-hand beta EEG–EMG coherence were positively correlated over time before training but became uncorrelated after training. This suggests that learning to bimanually produce a rhythmic musical pattern reinforces lateralised and segregated cortico-muscular communication., This work was supported by a grant from the Australian Research Council (DP170104322).

A growing body of research has been studying cognitive benefits that arise from music training in childhood or adulthood. Many studies focus specifically on the cognitive transfer of music training to language skill, with the aim of preventing language deficits and disorders and improving speech. However, predicted transfer effects are not always documented and not all findings replicate. While we acknowledge the important work that has been done in this field, we highlight the limitations of the persistent dichotomy between musicians and nonmusicians and argue that future research would benefit from a movement towards skill-based continua of musicianship instead of the currently widely practiced dichotomization of participants into groups of musicians and nonmusicians. Culturally situated definitions of musicianship as well as higher awareness of language diversity around the world are key to the understanding of potential cognitive transfers from music to language (and back). We outline a gradient approach to the study of the musical mind and suggest the next steps that could be taken to advance the field.

People have a natural and intrinsic ability to coordinate body movements with rhythms surrounding them, known as sensorimotor synchronisation. This can be observed in daily environments, when dancing or singing along with music, or spontaneously walking, talking or applauding in synchrony with one another. However, the neurophysiological mechanisms underlying accurately synchronised movement with selected rhythms in the environment remain unclear. Here we studied real and imagined sensorimotor synchronisation with interleaved auditory and visual rhythms using cortico-muscular coherence (CMC) to better understand the processes underlying the preparation and execution of synchronised movement. Electroencephalography (EEG), electromyography (EMG) from the finger flexors, and continuous force signals were recorded in 20 participants during tapping and imagined tapping with discrete stimulus sequences consisting of alternating auditory beeps and visual flashes. The results show that the synchronisation between cortical and muscular activity in the beta (14-38 Hz) frequency band becomes time-locked to the taps executed in synchrony with the visual and auditory stimuli. Dynamic modulation in CMC also occurred when participants imagined tapping with the visual stimuli, but with lower amplitude and a different temporal profile compared to real tapping. These results suggest that CMC does not only reflect changes related to the production of the synchronised movement, but also to its preparation, which appears heightened under higher attentional demands imposed when synchronising with the visual stimuli. These findings highlight a critical role of beta band neural oscillations in the cortical-muscular coupling underlying sensorimotor synchronisation.

Humans spontaneously synchronize their movements with external auditory rhythms such as a metronome or music. Although such synchronization preferentially occurs toward a simple 1:1 movement-sound frequency ratio, the parameters facilitating spontaneous synchronization to more complex frequency ratios remain largely unclear. The present study investigates the dynamics of spontaneous auditory-motor synchronization at a range of frequency ratios between movement and sound, and examines the benefit of simple accentuation pattern on synchronization emergence and stability. Participants performed index finger oscillations at their preferred tempo while listening to a metronome presented at either their preferred tempo, or twice or three times faster (frequency ratios of 1:1, 1:2 or 1:3) with different patterns of accentuation (unaccented, binary or ternary accented), and no instruction to synchronize. Participants' movements were spontaneously entrained to the auditory stimuli in the three different frequency ratio conditions. Moreover, the emergence and stability of the modes of coordination were influenced by the interaction between frequency ratio and pattern of accentuation. Coherent patterns, such as a 1:3 frequency ratio supported by a ternary accentuation, facilitated the emergence and stability of the corresponding mode of coordination. Furthermore, ternary accentuation induced a greater gain in stability for the corresponding mode of coordination than was observed with binary accentuation. Together, these findings demonstrate the importance of matching accentuation pattern and movement tempo for enhanced synchronization, opening new perspectives for stabilizing complex rhythmic motor behaviors, such as running.

When people engage in rhythmic joint actions, from simple clapping games to elaborate joint music making, they tend to increase their tempo unconsciously. Despite the rich literature on rhythmic performance in humans, the mechanisms underlying joint rushing are still unknown. We propose that joint rushing arises from the concurrent activity of two separate mechanisms. The phase advance mechanism was first proposed in research on synchronously flashing fireflies and chorusing insects. When this mechanism is combined with a human-specific period correction mechanism, the shortened periods of individual intervals are translated into a tempo increase. In three experiments, we investigated whether joint rushing can be reliably observed in a joint synchronization-continuation drumming task. Furthermore, we asked whether perceptual similarities produced by the actions of different individuals modulate the joint rushing effect. The results showed that joint rushing is a robust phenomenon occurring in groups of different sizes. Joint rushing was more pronounced when the action effects produced by different individuals were perceptually similar, supporting the assumption that a phase advance mechanism contributed to rushing. Further control conditions ruled out the alternative hypothesis that rushing during rhythmic interactions can be explained by social facilitation or action mirroring effects.

Acta psychologica 218, 103348 (2021). doi:10.1016/j.actpsy.2021.103348 special issue: "Current Issues in Joint Action Research / Edited by Robrecht Parsival Reinhard Diederik van der Wel, Cristina Becchio, Arianna Curioni, Thomas Wolf", Published by Elsevier, Amsterdam

Human rhythmic movements spontaneously synchronize with auditory rhythms at various frequency ratios. The emergence of more complex relationships—for instance, frequency ratios of 1:2 and 1:3—is enhanced by adding a congruent accentuation pattern (binary for 1:2 and ternary for 1:3), resulting in a 1:1 movement–accentuation relationship. However, this benefit of accentuation on movement synchronization appears to be stronger for the ternary pattern than for the binary pattern. Here, we investigated whether this difference in accent-induced movement synchronization may be related to a difference in the neural tracking of these accentuation profiles. Accented and control unaccented auditory sequences were presented to participants who concurrently produced finger taps at their preferred frequency, and spontaneous movement synchronization was measured. EEG was recorded during passive listening to each auditory sequence. The results revealed that enhanced movement synchronization with ternary accentuation was accompanied by enhanced neural tracking of this pattern. Larger EEG responses at the accentuation frequency were found for the ternary pattern compared with the binary pattern. Moreover, the amplitude of accent-induced EEG responses was positively correlated with the magnitude of accent-induced movement synchronization across participants. Altogether, these findings show that the dynamics of spontaneous auditory–motor synchronization is strongly driven by the multi-time-scale sensory processing of auditory rhythms, highlighting the importance of considering neural responses to rhythmic sequences for understanding and enhancing synchronization performance.

When listening to music, humans spontaneously perceive and synchronize movement to periodic pulses of meter. A growing body of evidence suggests that this widespread ability is related to neural processes that selectively enhance meter periodicities. However, to what extent these neural processes are affected by the attentional state of the listener remains largely unknown. Here, we recorded EEG while participants listened to auditory rhythms and detected small changes in tempo or pitch of the stimulus, or performed a visual task. The overall neural response to the auditory input decreased when participants attended the visual modality, indicating generally lower sensitivity to acoustic information. However, the selective contrast at meter periodicities did not differ across the three tasks. Moreover, this selective contrast could be trivially accounted for by biologically-plausible models of subcortical auditory processing, but only when meter periodicities were already prominent in the acoustic input. However, when meter periodicities were not prominent in the auditory input, the EEG responses could not be explained by low-level processing. This was also confirmed by early auditory responses that originate predominantly in early auditory areas and were recorded in the same EEG. The contrast at meter periodicities in these early responses was consistently smaller than in the EEG responses originating mainly from higher-level processing stages. Together, these results demonstrate that selective contrast at meter periodicities involves higher-level neural processes that may be engaged automatically, irrespective of behavioral context. This robust shaping of the neural representation of rhythm might thus contribute to spontaneous and effortless synchronization to musical meter in humans across cultures.

Because work songs are ubiquitous around the world, singing while working and performing a task with a coactor is presumably beneficial for both joint action and individual task performance. The present study investigated the impact of interpersonal rhythmic vocal interaction on interpersonal phase relations and on individual motor timing performance, which was evaluated by a synchronization-continuation paradigm requiring whole-body movement with or without visual contact. Participants repeated the syllable "tah" or remained silent in a manipulation of vocal interaction, and they were oriented toward or away from their partner to manipulate visual interaction. Results indicated the occurrence of spontaneous interpersonal coordination, evidenced by interpersonal phase relations that were closer to 0° and less variable when participants interacted both visually and vocally. At the individual level, visual interaction increased the variability of synchronization with the metronome but did not modulate the variability of continuation movements, whereas vocal interaction helped to decrease the variability of synchronization and continuation movements. Visual interaction therefore degraded individual movement timing while vocal interaction improved it. Communication via the auditory modality may play a compensatory role in naturalistic contexts where visual contact has potential destabilizing effects. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Human movements often spontaneously fall into synchrony with auditory and visual environmental rhythms. Related behavioral studies have shown that motor responses are automatically and unintentionally coupled with external rhythmic stimuli. However, the neurophysiological processes underlying such motor entrainment remain largely unknown. Here, we investigated with electroencephalography (EEG) and electromyography (EMG) the modulation of neural and muscular activity induced by periodic audio and/or visual sequences. The sequences were presented at either 1 or 2 Hz, while participants maintained constant finger pressure on a force sensor. The results revealed that although there was no change of amplitude in participants’ EMG in response to the sequences, the synchronization between EMG and EEG recorded over motor areas in the beta (12–40 Hz) frequency band was dynamically modulated, with maximal coherence occurring about 100 ms before each stimulus. These modulations in beta EEG–EMG motor coherence were found for the 2-Hz audio–visual sequences, confirming at a neurophysiological level the enhancement of motor entrainment with multimodal rhythms that fall within preferred perceptual and movement frequency ranges. Our findings identify beta band cortico-muscular coupling as a potential underlying mechanism of motor entrainment, further elucidating the nature of the link between sensory and motor systems in humans.

We investigated whether intravenous iron supplementation improves fatigue and general health in non-anemic repeat adult blood donors with iron deficiency (ferritin ≤ 50 µg/L). Of 1,487 potentially eligible participants, 203 were randomly assigned to a single intravenous dose of 800 mg iron-carboxymaltose and 202 to placebo; 393 participants completed the trial. At 6 to 8 weeks after intervention, self-rated mean fatigue scores (numeric rating scale from 1–10, primary outcome) were 3.9 ± 1.8 in the iron supplementation group and 4.0 ± 2.2 in the placebo group, showing no group difference (p = 0.819). Pre-specified subgroup analyses of gender, ferritin

When listening to music, people often perceive and move along with a periodic meter. However, the dynamics of mapping between meter perception and the acoustic cues to meter periodicities in the sensory input remain largely unknown. To capture these dynamics, we recorded the electroencephalography while nonmusician and musician participants listened to nonrepeating rhythmic sequences, where acoustic cues to meter frequencies either gradually decreased (from regular to degraded) or increased (from degraded to regular). The results revealed greater neural activity selectively elicited at meter frequencies when the sequence gradually changed from regular to degraded compared with the opposite. Importantly, this effect was unlikely to arise from overall gain, or low-level auditory processing, as revealed by physiological modeling. Moreover, the context effect was more pronounced in nonmusicians, who also demonstrated facilitated sensory-motor synchronization with the meter for sequences that started as regular. In contrast, musicians showed weaker effects of recent context in their neural responses and robust ability to move along with the meter irrespective of stimulus degradation. Together, our results demonstrate that brain activity elicited by rhythm does not only reflect passive tracking of stimulus features, but represents continuous integration of sensory input with recent context.

Music presents a complex case of movement timing, as one to several dozen musicians coordinate their actions at short time-scales. This process is often directed by a conductor who provides a visual beat and guides the ensemble through tempo changes. The current experiment tested the ways in which audio-motor coordination is influenced by visual cues from a conductor's gestures, and how this influence might manifest in two ways: movements used to produce sound related to the music, and movements of the upper-body that do not directly affect sound output. We designed a virtual conductor that was derived from morphed motion capture recordings of human conductors. Two groups of participants (29 musicians and 28 nonmusicians, to test the generalizability of visuo-motor synchronization to non-experts) were shown the virtual conductor, a simple visual metronome, or a stationary circle while completing a drumming task that required synchronization with tempo-changing musical sequences. We measured asynchronies and temporal anticipation in the drumming task, as well as participants' upper-body movement using motion capture. Drumming results suggest the conductor generally improves synchronization by facilitating anticipation of tempo changes in the music. Motion capture results showed that the conductor visual cue elicited more structured head movements than the other two visual cues for nonmusicians only. Multiple regression analysis showed that the nonmusicians with less rigid movement and high anticipation had lower asynchronies. Thus, the visual cues provided by a conductor might serve to facilitate temporal anticipation and more synchronous movement in the general population, but might also cause rigid ancillary movements in some non-experts.

Rhythmic movements produced by humans become spontaneously entrained to auditory rhythms in the environment. Evidence suggests that synchronisation to external auditory rhythms can contribute to the stabilisation of movements in time and space, opening new perspectives for motor training and rehabilitation. Here we compared the effects of single (1:1) and double (1:2) metronomes (i.e., one or two stimulations per preferred movement cycle) on spontaneous movement entrainment and stabilisation. We examined the spontaneous entrainment of self-paced hand-held pendulum swinging when single or double metronomes were presented either at the participant's preferred tempo or slightly slower or faster (± 10%). The results showed that participants' movements spontaneously entrained to auditory rhythms, and that the strength of this entrainment was the same for single and double metronomes. However, double metronomes decreased movement tempo stability, whereas single metronomes increased movement tempo stability compared to a control condition without a stimulus. These effects preferentially occurred for metronomes presented at participants' preferred movement tempi and especially for participants whose movements were intrinsically more variable. Participants' movement amplitude stability was also modulated in such a way that the stability of participants who were intrinsically less stable increased, whereas the stability of intrinsically more stable participants decreased with auditory rhythms, an effect that was stronger with double than single metronomes. Moreover, movement stabilisation in time and space were positively correlated, suggesting that tempo and amplitude stabilisation depend on similar processes and may be complementary. These findings provide new insight into the processes underlying auditory-motor entrainment and how auditory rhythms can be used to improve movement stability in time and space.

Perceptual coupling between people can lead to the spontaneous synchronisation of their rhythmic movements. In the current study, we hypothesised that the sight of a co-actor generates anchoring (local stabilisation around specific spatiotemporal points within movement cycles), and that such anchoring supports the occurrence and stability of spontaneous interpersonal synchronisation (global stabilisation across cycles). To test these hypotheses, we re-examined previously published data from a study where participants were required to perform auditory-motor coordination of whole-body movements with versus without visual contact. Paired participants performed two kinds of coordination task - either knee flexion or extension repeatedly with auditory metronome beats (Flexion-on-the-beat and Extension-on-the-beat conditions) while standing face-to-face or back-to-back to manipulate visual interaction. The analysis of individual movement trajectories showed that visual interaction led to decreased variability along the entire trajectory, except the maximum extension position. The results also indicated that the strength of this anchoring was correlated with the degree to which the variability of interpersonal phase relations decreased with visual coupling, suggesting that local stabilisation supported global interpersonal stabilisation. Therefore, the sight of a co-actor generates anchoring effects that may play a crucial role in the stabilisation of spontaneous interpersonal synchronisation.

Significance Bass sounds play a special role in conveying the rhythm and stimulating motor entrainment to the beat of music. However, the biological roots of this culturally widespread musical practice remain mysterious, despite its fundamental relevance in the sciences and arts, and also for music-assisted clinical rehabilitation of motor disorders. Here, we show that this musical convention may exploit a neurophysiological mechanism whereby low-frequency sounds shape neural representations of rhythmic input at the cortical level by boosting selective neural locking to the beat, thus explaining the privileged role of bass sounds in driving people to move along with the musical beat., Music makes us move, and using bass instruments to build the rhythmic foundations of music is especially effective at inducing people to dance to periodic pulse-like beats. Here, we show that this culturally widespread practice may exploit a neurophysiological mechanism whereby low-frequency sounds shape the neural representations of rhythmic input by boosting selective locking to the beat. Cortical activity was captured using electroencephalography (EEG) while participants listened to a regular rhythm or to a relatively complex syncopated rhythm conveyed either by low tones (130 Hz) or high tones (1236.8 Hz). We found that cortical activity at the frequency of the perceived beat is selectively enhanced compared with other frequencies in the EEG spectrum when rhythms are conveyed by bass sounds. This effect is unlikely to arise from early cochlear processes, as revealed by auditory physiological modeling, and was particularly pronounced for the complex rhythm requiring endogenous generation of the beat. The effect is likewise not attributable to differences in perceived loudness between low and high tones, as a control experiment manipulating sound intensity alone did not yield similar results. Finally, the privileged role of bass sounds is contingent on allocation of attentional resources to the temporal properties of the stimulus, as revealed by a further control experiment examining the role of a behavioral task. Together, our results provide a neurobiological basis for the convention of using bass instruments to carry the rhythmic foundations of music and to drive people to move to the beat.

The spontaneous ability to entrain to meter periodicities is central to music perception and production across cultures. There is increasing evidence that this ability involves selective neural responses to meter-related frequencies. This phenomenon has been observed in the human auditory cortex, yet it could be the product of evolutionarily older lower-level properties of brainstem auditory neurons, as suggested by recent recordings from rodent midbrain. We addressed this question by taking advantage of a new method to simultaneously record human EEG activity originating from cortical and lower-level sources, in the form of slow ( 150 Hz) responses to auditory rhythms. Cortical responses showed increased amplitudes at meter-related frequencies compared to meter-unrelated frequencies, regardless of the prominence of the meter-related frequencies in the modulation spectrum of the rhythmic inputs. In contrast, frequency-following responses showed increased amplitudes at meter-related frequencies only in rhythms with prominent meter-related frequencies in the input but not for a more complex rhythm requiring more endogenous generation of the meter. This interaction with rhythm complexity suggests that the selective enhancement of meter-related frequencies does not fully rely on subcortical auditory properties, but is critically shaped at the cortical level, possibly through functional connections between the auditory cortex and other, movement-related, brain structures. This process of temporal selection would thus enable endogenous and motor entrainment to emerge with substantial flexibility and invariance with respect to the rhythmic input in humans in contrast with non-human animals.

Sensorimotor synchronisation (SMS) is prevalent and readily studied in musical settings, as most people are able to perceive and synchronise with a beat (e.g., by finger tapping). We took an individual differences approach to understanding SMS to real music characterised by expressive timing (i.e., fluctuating beat regularity). Given the dynamic nature of SMS, we hypothesised that individual differences in working memory and auditory imagery—both fluid cognitive processes—would predict SMS at two levels: (1) mean absolute asynchrony (a measure of synchronisation error) and (2) anticipatory timing (i.e., predicting, rather than reacting to beat intervals). In Experiment 1, participants completed two working memory tasks, four auditory imagery tasks, and an SMS-tapping task. Hierarchical regression models were used to predict SMS performance, with results showing dissociations among imagery types in relation to mean absolute asynchrony, and evidence of a role for working memory in anticipatory timing. In Experiment 2, a new sample of participants completed an expressive timing perception task to examine the role of imagery in perception without action. Results suggest that imagery vividness is important for perceiving and control is important for synchronising with irregular but ecologically valid musical time series. Working memory is implicated in synchronising by anticipating events in the series.

The combination of frequency-tagging with electroencephalography (EEG) has recently proved fruitful for understanding the perception of beat and meter in musical rhythm, a common behavior shared by humans of all cultures. EEG frequency-tagging allows the objective measurement of input-output transforms to investigate beat perception, its modulation by exogenous and endogenous factors, development, and neural basis. Recent doubt has been raised about the validity of comparing frequency-domain representations of auditory rhythmic stimuli and corresponding EEG responses, assuming that it implies a one-to-one mapping between the envelope of the rhythmic input and the neural output, and that it neglects the sensitivity of frequency-domain representations to acoustic features making up the rhythms. Here we argue that these elements actually reinforce the strengths of the approach. The obvious fact that acoustic features influence the frequency spectrum of the sound envelope precisely justifies taking into consideration the sounds used to generate a beat percept for interpreting neural responses to auditory rhythms. Most importantly, the many-to-one relationship between rhythmic input and perceived beat actually validates an approach that objectively measures the input-output transforms underlying the perceptual categorization of rhythmic inputs. Hence, provided that a number of potential pitfalls and fallacies are avoided, EEG frequency-tagging to study input-output relationships appears valuable for understanding rhythm perception.

Spontaneous modulations of corticospinal excitability during action observation have been interpreted as evidence for the activation of internal motor representations equivalent to the observed action. Alternatively or complementary to this perspective, growing evidence shows that motor activity during observation of rhythmic movements can be modulated by direct visuomotor couplings and dynamical entrainment. In-phase and anti-phase entrainment spontaneously occur, characterized by cyclic movements proceeding simultaneously in the same (in-phase) or opposite (anti-phase) direction. Here we investigate corticospinal excitability during the observation of vertical oscillations of an index finger using Transcranial Magnetic Stimulation (TMS). Motor-evoked potentials (MEPs) were recorded from participants' flexor and extensor muscles of the right index finger, placed in either a maximal steady flexion or extension position, with stimulations delivered at maximal flexion, maximal extension or mid-trajectory of the observed finger oscillations. Consistent with the occurrence of dynamical motor entrainment, increased and decreased MEP responses - suggesting the facilitation of stable in-phase and anti-phase relations but not an unstable 90° phase relation - were found in participants' flexors. Anti-phase motor facilitation contrasts with the activation of internal motor representation as it involves activity in the motor system opposite from activity required for the execution of the observed movement. These findings demonstrate the relevance of dynamical entrainment theories and methods for understanding spontaneous motor activity in the brain during action observation and the mechanisms underpinning coordinated movements during social interaction.

Human rhythmic movements spontaneously entrain to external rhythmic stimuli. Such sensory-motor entrainment can attract movements to different tempi and enhance their efficiency, with potential clinical applications for motor rehabilitation. Here we investigate whether entrainment of self-paced rhythmic movements can be induced via transcranial alternating current stimulation (tACS), which uses alternating currents to entrain spontaneous brain oscillations at specific frequencies. Participants swung a handheld pendulum at their preferred tempo with the right hand while tACS was applied over their left or right primary motor cortex at frequencies equal to their preferred tempo (Experiment 1) or in the alpha (10Hz) and beta (20Hz) ranges (Experiment 2). Given that entrainment generally occurs only if the frequency difference between two rhythms is small, stimulations were delivered at frequencies equal to participants' preferred movement tempo (≈1Hz) and ±12.5% in Experiment 1, and at 10Hz and 20Hz, and ±12.5% in Experiment 2. The comparison of participants' movement frequency, amplitude, variability, and phase synchrony with and without tACS failed to reveal entrainment or movement modifications across the two experiments. However, significant differences in stimulation-related side effects reported by participants were found between the two experiments, with phosphenes and burning sensations principally occurring in Experiment 2, and metallic tastes reported marginally more often in Experiment 1. Although other stimulation protocols may be effective, our results suggest that rhythmic movements such as pendulum swinging or locomotion that are low in goal-directedness and/or strongly driven by peripheral and mechanical constraints may not be susceptible to modulation by tACS.

Synchronous movement is a key component of social behavior in several species including humans. Recent theories have suggested a link between interpersonal synchrony of brain oscillations and interpersonal movement synchrony. The present study investigated this link. Using transcranial alternating current stimulation (tACS) applied over the left motor cortex, we induced beta band (20 Hz) oscillations in pairs of individuals who both performed a finger-tapping task with the right hand. In-phase or anti-phase oscillations were delivered during a preparatory period prior to movement and while the tapping task was performed. In-phase 20 Hz stimulation enhanced interpersonal movement synchrony, compared with anti-phase or sham stimulation, particularly for the initial taps following the preparatory period. This was confirmed in an analysis comparing real vs pseudo pair surrogate data. No enhancement was observed for stimulation frequencies of 2 Hz (matching the target movement frequency) or 10 Hz (alpha band). Thus, phase-coupling of beta band neural oscillations across two individuals’ (resting) motor cortices supports the interpersonal alignment of sensorimotor processes that regulate rhythmic action initiation, thereby facilitating the establishment of synchronous movement. Phase-locked dual brain stimulation provides a promising method to study causal effects of interpersonal brain synchrony on social, sensorimotor and cognitive processes.