The role of temporal prediction abilities in interpersonal sensorimotor synchronization

Sensorimotor Impairment in Aging and Neurocognitive Disorders: Beat Synchronization and Adaptation to Tempo Changes

Background

Understanding the nature and extent of sensorimotor decline in aging individuals and those with neurocognitive disorders (NCD), such as Alzheimer's disease, is essential for designing effective music-based interventions. Our understanding of rhythmic functions remains incomplete, particularly in how aging and NCD affect sensorimotor synchronization and adaptation to tempo changes.

Objective

This study aimed to investigate how aging and NCD severity impact tapping to metronomes and music, with and without tempo changes.

Methods

Patients from a memory clinic participated in a tapping task, synchronizing with metronomic and musical sequences, some of which contained sudden tempo changes. After exclusions, 51 patients were included in the final analysis.

Results

Participants' Mini-Mental State Examination scores were associated with tapping consistency. Additionally, age negatively influenced consistency when synchronizing with a musical beat, whereas consistency remained stable across age when tapping with a metronome.

Conclusions

The results indicate that the initial decline of attention and working memory with age may impact perception and synchronization to a musical beat, whereas progressive NCD-related cognitive decline results in more widespread sensorimotor decline, affecting tapping irrespective of audio type. These findings underline the importance of customizing rhythm-based interventions to the needs of older adults and individuals with NCD, taking into consideration their cognitive as well as their rhythmic aptitudes.

Subtle Patterns of Altered Responsiveness to Delayed Auditory Feedback during Finger Tapping in People Who Stutter

Differences in sensorimotor integration mechanisms have been observed between people who stutter (PWS) and controls who do not. Delayed auditory feedback (DAF) introduces timing discrepancies between perception and action, disrupting sequence production in verbal and non-verbal domains. While DAF consistently enhances speech fluency in PWS, its impact on non-verbal sensorimotor synchronization abilities remains unexplored. A total of 11 PWS and 13 matched controls completed five tasks: (1) unpaced tapping; (2) synchronization-continuation task (SCT) without auditory feedback; (3) SCT with DAF, with instruction either to align the sound in time with the metronome; or (4) to ignore the sound and align their physical tap to the metronome. Additionally, we measured participants' sensitivity to detecting delayed feedback using a (5) delay discrimination task. Results showed that DAF significantly affected performance in controls as a function of delay duration, despite being irrelevant to the task. Conversely, PWS performance remained stable across delays. When auditory feedback was absent, no differences were found between PWS and controls. Moreover, PWS were less able to detect delays in speech and tapping tasks. These findings show subtle differences in non-verbal sensorimotor performance between PWS and controls, specifically when action-perception loops are disrupted by delays, contributing to models of sensorimotor integration in stuttering.

Interpersonal motor synchrony in autism: a systematic review and meta-analysis

Introduction

Interpersonal motor synchrony (IMS) is the spontaneous, voluntary, or instructed coordination of movements between interacting partners. Throughout the life cycle, it shapes social exchanges and interplays with intra- and inter-individual characteristics that may diverge in Autism Spectrum Disorder (ASD). Here we perform a systematic review and meta-analysis to summarize the extant literature and quantify the evidence about reduced IMS in dyads including at least one participant with a diagnosis of ASD.

Methods

Empirical evidence from sixteen experimental studies was systematically reviewed, encompassing spontaneous and instructed paradigms as well as a paucity of measures used to assess IMS. Of these, thirteen studies (n = 512 dyads) contributed measures of IMS with an in situ neurotypical partner (TD) for ASD and control groups, which could be used for meta-analyses.

Results

Reduced synchronization in ASD-TD dyads emerged from both the systematic review and meta-analyses, although both small and large effect sizes (i.e., Hedge's g) in favor of the control group are consistent with the data (Hedge's g = .85, p < 0.001, 95% CI[.35, 1.35], 95% PI[-.89, 2.60]).

Discussion

Uncertainty is discussed relative to the type of task, measures, and age range considered in each study. We further discuss that sharing similar experiences of the world might help to synchronize with one another. Future studies should not only assess whether reduced IMS is consistently observed in ASD-TD dyads and how this shapes social exchanges, but also explore whether and how ASD-ASD dyads synchronize during interpersonal exchanges.

Music Rhythmic Cueing for the Production of Non-native Speech Rhythm: Evidence from Chinese Learners of French

The present study examined the cross-modal cueing effect of musical rhythmic beats on non-native speech rhythm production. Two groups of Chinese learners of French were cued respectively with rhythmic beats that either matched (matching group) or mismatched (mismatching group) the rhythm patterns of the target French sentences. The participants were asked to produce the target sentences after cueing and their speech production was compared with their baseline condition in which no cueing was used. The results showed that the matching group produced the target French rhythm significantly better after cueing with musical rhythmic beats that matched the French rhythm, in contrast to the mismatching group where no significant improvement was found. Individual differences in auditory short-term memory and rhythmic skills were not related to improvement in producing French rhythm after cueing. The results suggest that musical rhythmic cueing can be used to improve non-native speech rhythm production, further indicating a close link between speech and music in the temporal domain.

Dynamics in interbrain synchronization while playing a piano duet

Humans interact with each other through actions that are implemented by sensory and motor processes. To investigate the role of interbrain synchronization emerging during interpersonal action coordination, electroencephalography data from 13 pairs of pianists were recorded simultaneously while they performed a duet together. The study aimed to investigate whether interbrain phase couplings can be reduced to similar bottom-up driven processes during synchronous play, or rather represent cognitive top-down control required during periods of higher coordination demands. To induce such periods, one of the musicians acted as a confederate who deliberately desynchronized the play. As intended, on the behavioral level, the perturbation caused a breakdown in the synchronization of the musicians' play and in its stability across trials. On the brain level, interbrain synchrony, as measured by the interbrain phase coherence (IPC), increased in the delta and theta frequency bands during perturbation as compared to non-perturbed trials. Interestingly, this increase in IPC in the delta band was accompanied by the shift of the phase difference angle from in-phase toward anti-phase synchrony. In conclusion, the current study demonstrates that interbrain synchronization is based on the interpersonal temporal alignment of different brain mechanisms and is not simply reducible to similar sensory or motor responses.

Preceding and trailing role-taking in dyad synchronization using finger tapping

In ensembles, people synchronize the timings of their movements with those of others. Players sometimes take on preceding and trailing roles, whereby one's beat is either slightly earlier or slightly later than that of another. In this study, we aimed to clarify whether the division of preceding and trailing roles occurs in simple rhythmic coordination among non-musicians. Additionally, we investigated the temporal dependencies between these roles. We conducted a synchronous-continuous tapping task involving pairs of people, whereby pairs of participants first tapped to synchronize with a metronome. After the metronome stopped, the participants synchronized their taps to their partners' tap timings, which were presented as auditory stimuli. Except in one trial, the pairs involved participants taking on preceding and trailing roles. Compared to the participants taking on the trailing role, those taking on the preceding role demonstrated enhanced phase-correction responses, while those taking on the trailing role significantly adapted their tempos to match those of their partners. As a result, people spontaneously divided into preceding and trailing roles. The preceding participants tended to reduce asynchronies, while the trailing participants tended to match their tempo to their partners'.

Can rhythm-mediated reward boost learning, memory, and social connection? Perspectives for future research

Studies of rhythm processing and of reward have progressed separately, with little connection between the two. However, consistent links between rhythm and reward are beginning to surface, with research suggesting that synchronization to rhythm is rewarding, and that this rewarding element may in turn also boost this synchronization. The current mini review shows that the combined study of rhythm and reward can be beneficial to better understand their independent and combined roles across two central aspects of cognition: 1) learning and memory, and 2) social connection and interpersonal synchronization; which have so far been studied largely independently. From this basis, it is discussed how connections between rhythm and reward can be applied to learning and memory and social connection across different populations, taking into account individual differences, clinical populations, human development, and animal research. Future research will need to consider the rewarding nature of rhythm, and that rhythm can in turn boost reward, potentially enhancing other cognitive and social processes.

Brain networks for temporal adaptation, anticipation, and sensory-motor integration in rhythmic human behavior

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.

The role of reciprocity in dynamic interpersonal coordination of physiological rhythms

A central question in social cognition research is how people coordinate their bodily rhythms, and how important reciprocity of interaction is for interpersonal coordination. Previous research has primarily focused on interpersonal action coordination, which has been shown to be facilitated by mechanisms of prediction and mutual adaption. Recent research is beginning to show that people also coordinate their physiological rhythms (i.e., respiration, heart rhythms) when they engage in natural forms of social interaction, such as conversation, choir singing, and rituals. However, the mechanisms underlying interpersonal physiological synchronization remain obscure, and could provide insight into the dynamic mechanisms that underlie continuous and regulatory, rather than instrumental, joint actions. Using real-time biofeedback, we investigated whether people synchronize their respiration rhythms by forming a joint dynamical system through reciprocity of interaction, or by producing more predictable respiration rhythms. Our results show that people are more in-phase synchronized but less phase-locked when interacting bidirectionally versus unidirectionally (online), but there is no difference in synchronization during reciprocal interaction and when adapting unidirectionally (offline) to recordings of respiration signals that emerged during the reciprocal interaction. Moreover, the strength of synchronization is driven by the predictability of the respiration rhythms that emerge in the bidirectional interaction - specifically, the slowing of breathing rhythms and stability of breathing frequencies - rather than the online mutual adaptation itself. These results suggest that coordination is facilitated by the emergence of predictable breathing patterns, rather than reciprocity itself.

Magnetoencephalography recordings reveal the spatiotemporal dynamics of recognition memory for complex versus simple auditory sequences

Auditory recognition is a crucial cognitive process that relies on the organization of single elements over time. However, little is known about the spatiotemporal dynamics underlying the conscious recognition of auditory sequences varying in complexity. To study this, we asked 71 participants to learn and recognize simple tonal musical sequences and matched complex atonal sequences while their brain activity was recorded using magnetoencephalography (MEG). Results reveal qualitative changes in neural activity dependent on stimulus complexity: recognition of tonal sequences engages hippocampal and cingulate areas, whereas recognition of atonal sequences mainly activates the auditory processing network. Our findings reveal the involvement of a cortico-subcortical brain network for auditory recognition and support the idea that stimulus complexity qualitatively alters the neural pathways of recognition memory.

Follow the sound of my violin: Granger causality reflects information flow in sound

Recent research into how musicians coordinate their expressive timing, phrasing, articulation, dynamics, and other stylistic characteristics during performances has highlighted the role of predictive processes, as musicians must anticipate how their partners will play in order to be together. Several studies have used information flow techniques such as Granger causality to show that upcoming movements of a musician can be predicted from immediate past movements of fellow musicians. Although musicians must move to play their instruments, a major goal of music making is to create a joint interpretation through the sounds they produce. Yet, information flow techniques have not been applied previously to examine the role that fellow musicians' sound output plays in these predictive processes and whether this changes as they learn to play together. In the present experiment, we asked professional violinists to play along with recordings of two folk pieces, each eight times in succession, and compared the amplitude envelopes of their performances with those of the recordings using Granger causality to measure information flow and cross-correlation to measure similarity and synchronization. In line with our hypotheses, our measure of information flow was higher from the recordings to the performances than vice versa, and decreased as the violinists became more familiar with the recordings over trials. This decline in information flow is consistent with a gradual shift from relying on auditory cues to predict the recording to relying on an internally-based (learned) model built through repetition. There was also evidence that violinists became more synchronized with the recordings over trials. These results shed light on the planning and learning processes involved in the aligning of expressive intentions in group music performance and lay the groundwork for the application of Granger causality to investigate information flow through sound in more complex musical interactions.

Effects of Warm-up Focused on the Mind-Body on Choral Performance

OBJECTIVE

In choral performance, a wide variety of musical expression is required to deliver the worldview of the work to the audience. Singers need to regulate their mind-body to be in the optimal state, which includes relaxed concentration and flexible kinesthetic controllability in sensation, expression, and vocalization, for the chorus. Therefore, a choral warm-up focused on the mind-body could be crucial for various musical expressions. However, what kind of warm-up helps the singer achieve the optimal condition for the chorus remains unclear. Here, we investigated the effects of a warm-up method focusing on breathing, physical movement, imagery, and the combination of those factors on singing performance.

METHOD

Twenty-five choral singers were randomly assigned to five groups, and then singers for each group online conducted one of five warm-up conditions (breathing / stretching / imagery work / all works / control) and performed singing tasks to evaluate singing performance, including sensation, expression, and vocalization, both subjectively and objectively. Changes in mood were also measured using the second edition of the Profile of Mood States.

RESULTS

The results showed that the warm-up with imagery work or all works could objectively and subjectively enhance singing performance. By contrast, the warm-up with breathing or stretching did not significantly improve performance, but did enhance subjective evaluations in general. In addition, no significant correlations were found between the objective performance evaluations and changes in individual mood.

CONCLUSIONS

These results suggest that a warm-up focusing on mind-body interventions, especially imagery work, may enhance choral performance, thereby providing new insight for the establishment of more effective choral warm-up methods.

When action prediction grows old: An fMRI study

Predicting the unfolding of others' actions (action prediction) is crucial for successfully navigating the social world and interacting efficiently. Age-related changes in this domain have remained largely unexplored, especially for predictions regarding simple gestures and independent of contextual information or motor expertise. Here, we evaluated whether healthy aging impacts the neurophysiological processes recruited to anticipate, from the observation of implied-motion postures, the correct conclusion of simple grasping and pointing actions. A color-discrimination task served as a control condition to assess the specificity of the age-related effects. Older adults showed reduced efficiency in performance that was yet not specific to the action prediction task. Nevertheless, fMRI results revealed task-specific age-related differences: while both groups showed stronger recruitment of the lateral occipito-temporal cortex bilaterally during the action prediction than the control task, the younger participants additionally showed a higher bilateral engagement of parietal regions. Importantly, in both groups, the recruitment of visuo-motor processes in the right posterior parietal cortex was a predictor of good performance. These results support the hypothesis of decreased involvement of sensorimotor processes in cognitive tasks when processing action- and body-related stimuli in healthy aging. These results have implications for social interaction, which requires the fast reading of others' gestures.

The Components of Interpersonal Synchrony in the Typical Population and in Autism: A Conceptual Analysis

Interpersonal synchrony – the tendency for social partners to temporally co-ordinate their behaviour when interacting – is a ubiquitous feature of social interactions. Synchronous interactions play a key role in development, and promote social bonding and a range of pro-social behavioural outcomes across the lifespan. The process of achieving and maintaining interpersonal synchrony is highly complex, with inputs required from across perceptual, temporal, motor, and socio-cognitive domains. In this conceptual analysis, we synthesise evidence from across these domains to establish the key components underpinning successful non-verbal interpersonal synchrony, how such processes interact, and factors that may moderate their operation. We also consider emerging evidence that interpersonal synchrony is reduced in autistic populations. We use our account of the components contributing to interpersonal synchrony in the typical population to identify potential points of divergence in interpersonal synchrony in autism. The relationship between interpersonal synchrony and broader aspects of social communication in autism are also considered, together with implications for future research.

Mutual beta power modulation in dyadic entrainment

Across a broad spectrum of interactions, humans exhibit a prominent tendency to synchronize their movements with one another. Traditionally, this phenomenon has been explained from the perspectives of predictive coding or dynamical systems theory. While these theories diverge with respect to whether individuals hold internal models of each other, they both assume a predictive or anticipatory mechanism enabling rhythmic interactions. However, the neural bases underpinning interpersonal synchronization are still a subject under active investigation. Here we provide evidence that the brain relies on a common oscillatory mechanism to pace self-generated rhythmic movements and to track the movements produced by a partner. By performing dual-electroencephalography recordings during a joint finger-tapping task, we identified an oscillatory component in the beta range (∼ 20 Hz), which was significantly modulated by both self-generated and other-generated movement. In conditions where the partners perceived each other, we observed periodic fluctuations of beta power as a function of the reciprocal movement cycles. Crucially, this modulation occurred both in visually and in auditorily coupled conditions, and was accompanied by recurrent periods of dyadic synchronized behavior. Our results show that periodic beta power modulations may be a critical mechanism underlying interpersonal synchronization, possibly enabling mutual predictions between coupled individuals, leading to co-regulation of timing and overt mutual adaptation. Our findings thus provide a potential bridge between influential theories attempting to explain interpersonal coordination, and a concrete connection to its neurophysiological bases.

Neural correlates with individual differences in temporal prediction during auditory-motor synchronization

Temporal prediction ability is vital for movement synchronization with external rhythmic stimuli (sensorimotor synchronization); however, little is known regarding individual variations in temporal prediction ability and its neural correlates. We determined the underlying neural correlates of temporal prediction and individual variations during auditory-motor synchronization. We hypothesized that the non-primary motor cortices, such as the premotor cortex and supplementary motor area, are the key brain regions that correlate individual variations in prediction ability. Functional magnetic resonance imaging (7T) was performed for 18 healthy volunteers who tapped to 3 types of auditory metronome beats: isochronous, tempo change, and random. The prediction ability was evaluated using prediction/tracking ratios that were computed based on cross-correlations between tap timing and pacing events. Participants with a higher prediction/tracking ratio (i.e. stronger predictive tendency) tapped to metronome beats more accurately and precisely. The prediction/tracking ratio was positively correlated with the activity in the bilateral dorsal premotor cortex (PMd), suggesting that the bilateral PMd explains the individual variation in prediction ability. These results indicate that the PMd is involved in generating a model for temporal prediction of auditory rhythm patterns and its activity would reflect model accuracy, which is critical for accurate and precise sensorimotor synchronization.

Sensorimotor Synchronization in Healthy Aging and Neurocognitive Disorders

Sensorimotor synchronization (SMS), the coordination of physical actions in time with a rhythmic sequence, is a skill that is necessary not only for keeping the beat when making music, but in a wide variety of interpersonal contexts. Being able to attend to temporal regularities in the environment is a prerequisite for event prediction, which lies at the heart of many cognitive and social operations. It is therefore of value to assess and potentially stimulate SMS abilities, particularly in aging and neurocognitive disorders (NCDs), to understand intra-individual communication in the later stages of life, and to devise effective music-based interventions. While a bulk of research exists about SMS and movement-based interventions in Parkinson's disease, a lot less is known about other types of neurodegenerative disorders, such as Alzheimer's disease, vascular dementia, or frontotemporal dementia. In this review, we outline the brain and cognitive mechanisms involved in SMS with auditory stimuli, and how they might be subject to change in healthy and pathological aging. Globally, SMS with isochronous sounds is a relatively well-preserved skill in old adulthood and in patients with NCDs. At the same time, natural tapping speed decreases with age. Furthermore, especially when synchronizing to sequences at slow tempi, regularity and precision might be lower in older adults, and even more so in people with NCDs, presumably due to the fact that this process relies on attention and working memory resources that depend on the prefrontal cortex and parietal areas. Finally, we point out that the effect of the severity and etiology of NCDs on sensorimotor abilities is still unclear: More research is needed with moderate and severe NCD, comparing different etiologies, and using complex auditory signals, such as music.

Stepping in time: Alpha-mu and beta oscillations during a walking synchronization task

Interpersonal behavioral synchrony is referred to as temporal coordination of action between two or more individuals. Humans tend to synchronize their movements during repetitive movement tasks such as walking. Mobile EEG technology now allows us to examine how this happens during gait. 18 participants equipped with foot accelerometers and mobile EEG walked with an experimenter in three conditions: With their view of the experimenter blocked, walking naturally, and trying to synchronize their steps with the experimenter. The experimenter walked following a headphone metronome to keep their steps consistent for all conditions. Step behavior and synchronization between the experimenter and participant were compared between conditions. Additionally, event-related spectral perturbations (ERSPs) were time-warped to the gait cycle in order to analyze alpha-mu (7.5-12.5 Hz) and beta (16-32 Hz) rhythms over the whole gait cycle. Step synchronization was significantly higher in the synchrony condition than in the natural condition. Likewise regarding ERSPs, right parietal channel (C4, C6, CP4, CP6) alpha-mu and central channel (C1, Cz, C2) beta power were suppressed from baseline in the walking synchrony condition compared to the natural walking condition. The natural and blocked conditions were not found to be significantly different in behavioral or spectral comparisons. Our results are compatible with the view that intentional synchronization employs systems associated with social interaction as well as the central motor system.

Joint rushing alters internal timekeeping in non-musicians and musicians

Recent studies have shown that people engaging in joint rhythmic activity unintentionally increase their tempo. The same tempo increase does not occur when the same rhythmic activity is performed alone. This phenomenon is known as joint rushing. In two experiments, we investigated whether joint rushing is caused by correction mechanisms that facilitate sensorimotor synchronization. Because such correction mechanisms require perceptual input, joint rushing should discontinue when auditory feedback in a joint rhythmic activity is interrupted. This prediction was clearly supported in two experiments, one with musicians and one with non-musicians. Surprisingly, there was no indication that the amount of joint rushing differed between musicians and non-musicians. Furthermore, neither musicians nor non-musicians were able to return to the initially instructed tempo after feedback had been interrupted. This result indicates that joint rushing has a lasting effect on an internal timekeeper. An important question for future research is whether joint rushing is only a dysfunctional side effect of the way sensorimotor synchronization works or whether it has a function in enabling precise temporal coordination between different individuals.

Temporal Coordination in Piano Duet Networked Music Performance (NMP): Interactions Between Acoustic Transmission Latency and Musical Role Asymmetries

Today’s audio, visual, and internet technologies allow people to interact despite physical distances, for casual conversation, group workouts, or musical performance. Musical ensemble performance is unique because interaction integrity critically depends on the timing between each performer’s actions and when their acoustic outcomes arrive. Acoustic transmission latency (ATL) between players is substantially longer for networked music performance (NMP) compared to traditional in-person spaces where musicians can easily adapt. Previous work has shown that longer ATLs slow the average tempo in ensemble performance, and that asymmetric co-actor roles and empathy-related traits affect coordination patterns in joint action. Thus, we are interested in how musicians collectively adapt to a given latency and how such adaptation patterns vary with their task-related and person-related asymmetries. Here, we examined how two pianists performed duets while hearing each other’s auditory outcomes with an ATL of 10, 20, or 40 ms. To test the hypotheses regarding task-related asymmetries, we designed duets such that pianists had: (1) a starting or joining role and (2) a similar or dissimilar musical part compared to their co-performer, with respect to pitch range and melodic contour. Results replicated previous clapping-duet findings showing that longer ATLs are associated with greater temporal asynchrony between partners and increased average tempo slowing. While co-performer asynchronies were not affected by performer role or part similarity, at the longer ATLs starting performers displayed slower tempos and smaller tempo variability than joining performers. This asymmetry of stability vs. flexibility between starters and joiners may sustain coordination, consistent with recent joint action findings. Our data also suggest that relative independence in musical parts may mitigate ATL-related challenges. Additionally, there may be a relationship between co-performer differences in empathy-related personality traits such as locus of control and coordination during performance under the influence of ATL. Incorporating the emergent coordinative dynamics between performers could help further innovation of music technologies and composition techniques for NMP.

Mapping between sound, brain and behaviour: four-level framework for understanding rhythm processing in humans and non-human primates

Humans perceive and spontaneously move to one or several levels of periodic pulses (a meter, for short) when listening to musical rhythm, even when the sensory input does not provide prominent periodic cues to their temporal location. Here, we review a multi-levelled framework to understanding how external rhythmic inputs are mapped onto internally represented metric pulses. This mapping is studied using an approach to quantify and directly compare representations of metric pulses in signals corresponding to sensory inputs, neural activity and behaviour (typically body movement). Based on this approach, recent empirical evidence can be drawn together into a conceptual framework that unpacks the phenomenon of meter into four levels. Each level highlights specific functional processes that critically enable and shape the mapping from sensory input to internal meter. We discuss the nature, constraints and neural substrates of these processes, starting with fundamental mechanisms investigated in macaque monkeys that enable basic forms of mapping between simple rhythmic stimuli and internally represented metric pulse. We propose that human evolution has gradually built a robust and flexible system upon these fundamental processes, allowing more complex levels of mapping to emerge in musical behaviours. This approach opens promising avenues to understand the many facets of rhythmic behaviours across individuals and species. This article is part of the theme issue 'Synchrony and rhythm interaction: from the brain to behavioural ecology'.

The effects of dual-task interference in predicting turn-ends in speech and music

Determining when a partner's spoken or musical turn will end requires well-honed predictive abilities. Evidence suggests that our motor systems are activated during perception of both speech and music, and it has been argued that motor simulation is used to predict turn-ends across domains. Here we used a dual-task interference paradigm to investigate whether motor simulation of our partner's action underlies our ability to make accurate turn-end predictions in speech and in music. Furthermore, we explored how specific this simulation is to the action being predicted. We conducted two experiments, one investigating speech turn-ends, and one investigating music turn-ends. In each, 34 proficient pianists predicted turn-endings while (1) passively listening, (2) producing an effector-specific motor activity (mouth/hand movement), or (3) producing a task- and effector-specific motor activity (mouthing words/fingering a piano melody). In the speech experiment, any movement during speech perception disrupted predictions of spoken turn-ends, whether the movement was task-specific or not. In the music experiment, only task-specific movement (i.e., fingering a piano melody) disrupted predictions of musical turn-ends. These findings support the use of motor simulation to make turn-end predictions in both speech and music but suggest that the specificity of this simulation may differ between domains.

Simultaneous self-other integration and segregation support real-time interpersonal coordination in a musical joint action task

The ability to distinguish between an individual's own actions and those of another person is a requirement for successful joint action, particularly in domains such as group music making where precise interpersonal coordination ensures perceptual overlap in the effects of co-performers' actions. We tested the hypothesis that such coordination benefits from simultaneous integration and segregation of information about 'self' and 'other' in an experiment using a musical joint action paradigm. Sixteen pairs of individuals with little or no musical training performed a dyadic synchronization task on a pair of electronic music boxes. The relationship between pitches produced by paired participants (same vs. different) and the relationship between movement frequencies required to trigger synchronous tones (congruent vs. incongruent) were varied in a repeated measures design. The results indicate that interpersonal coordination was most accurate when sounds were different in pitch but movement frequency was congruent. Under other conditions, participants often drifted apart, resulting in poor coordination, especially with same sounds and incongruent movements across co-performers. These findings suggest that interpersonal coordination was facilitated when simultaneous self-other integration and segregation occurred across sensory modalities in an asymmetrical manner where pitch relations favoured segregation via auditory streaming while movement congruence favoured integration via visuo-motor coupling. Such self-other representational balance may enable co-performers to maintain autonomous control while attending, anticipating, and adapting to each other's timing when joint action requires precise temporal coordination.

Reciprocity and alignment: quantifying coupling in dynamic interactions

Recent accounts of social cognition focus on how we do things together, suggesting that becoming aligned relies on a reciprocal exchange of information. The next step is to develop richer computational methods that quantify the degree of coupling and describe the nature of the information exchange. We put forward a definition of coupling, comparing it to related terminology and detail, available computational methods and the level of organization to which they pertain, presenting them as a hierarchy from weakest to richest forms of coupling. The rationale is that a temporally coherent link between two dynamical systems at the lowest level of organization sustains mutual adaptation and alignment at the highest level. Postulating that when we do things together, we do so dynamically over time and we argue that to determine and measure instances of true reciprocity in social exchanges is key. Along with this computationally rich definition of coupling, we present challenges for the field to be tackled by a diverse community working towards a dynamic account of social cognition.

Interpersonal Synchronization Processes in Discrete and Continuous Tasks

Three frameworks have been proposed to account for interpersonal synchronization: The information processing approach argues that synchronization is achieved by mutual adaptation, the coordination dynamics perspective supposes a continuous coupling between systems, and complexity matching suggests a global, multi-scale interaction. We hypothesized that the relevancy of these models was related to the nature of the performed tasks. 10 dyads performed synchronized tapping and synchronized forearm oscillations, in two conditions: full (participants had full information about their partner), and digital (information was limited to discrete auditory signals). Results shows that whatever the task and the available information, synchronization was dominated by a discrete mutual adaptation. These results question the relevancy of the coordination dynamics perspective in interpersonal coordination.

The influence of a conductor and co-performer on auditory-motor synchronisation, temporal prediction, and ancillary entrainment in a musical drumming task

Interpersonal coordination is exemplified in ensemble musicians, who coordinate their actions deliberately in order to achieve temporal synchronisation in their performances. However, musicians also move parts of their bodies unintentionally or spontaneously, sometimes in ways that do not directly produce sound from their instruments. Musicians' movements-intentional or otherwise-provide visual signals to co-performers, which might facilitate temporal synchronisation. In large ensembles, a conductor also provides a visual cue, which has been shown to enhance synchronisation. In the present study, we tested how visual cues from a co-performer and a conductor affect processes of temporal anticipation, synchronisation, and ancillary movements in a sample of primarily non-musicians. We used a dyadic synchronisation drumming task, in which paired participants drummed to the beat of tempo-changing music. We manipulated visual access between partners and a virtual conductor. Results showed that the conductor improved synchronisation with the music, but synchrony with the music did not improve when partners could see each other. Temporal prediction was improved when partners saw the conductor, but not each other. Ancillary movements of the head were more synchronised between partners when they could see each other, and greater ancillary synchrony at beat-related frequencies of movement was associated with greater drumming synchrony. These results suggest that compatible audio-visual cues can improve intentional synchronisation, that ancillary movements are affected by seeing a partner, and that attended vs. incidental visual cues thus have partially dissociable effects on temporal coordination during joint action.

Induced Beta Power Modulations during Isochronous Auditory Beats Reflect Intentional Anticipation before Gradual Tempo Changes

Induced beta-band power modulations in auditory and motor-related brain areas have been associated with automatic temporal processing of isochronous beats and explicit, temporally-oriented attention. Here, we investigated how explicit top-down anticipation before upcoming tempo changes, a sustained process commonly required during music performance, changed beta power modulations during listening to isochronous beats. Musicians’ electroencephalograms were recorded during the task of anticipating accelerating, decelerating, or steady beats after direction-specific visual cues. In separate behavioural testing for tempo-change onset detection, such cues were found to facilitate faster responses, thus effectively inducing high-level anticipation. In the electroencephalograms, periodic beta power reductions in a frontocentral topographic component with seed-based source contributions from auditory and sensorimotor cortices were apparent after isochronous beats with anticipation in all conditions, generally replicating patterns found previously during passive listening to isochronous beats. With anticipation before accelerations, the magnitude of the power reduction was significantly weaker than in the steady condition. Between the accelerating and decelerating conditions, no differences were found, suggesting that the observed beta patterns may represent an aspect of high-level anticipation common before both tempo changes, like increased attention. Overall, these results indicate that top-down anticipation influences ongoing auditory beat processing in beta-band networks.

Musical training enhances temporal adaptation of auditory-motor synchronization

To coordinate their actions successfully with auditory events, individuals must be able to adapt their behaviour flexibly to environmental changes. Previous work has shown that musical training enhances the flexibility to synchronize behaviour with a wide range of stimulus periods. The current experiment investigated whether musical training enhances temporal adaptation to period perturbations as listeners tapped with a metronome, and whether this enhancement is specific to individuals' Spontaneous Production Rates (SPRs; individuals' natural uncued rates). Both musicians and nonmusicians adapted more quickly to period perturbations that slowed down than to those that sped up. Importantly, musicians adapted more quickly to all period perturbations than nonmusicians. Fits of a damped harmonic oscillator model to the tapping measures confirmed musicians' faster adaptation and greater responsiveness to period perturbations. These results suggest that, even when the task is tailored to individual SPRs, musical training increases the flexibility with which individuals can adapt to changes in their environment during auditory-motor tasks.

Spatiotemporal perturbations in paced finger tapping suggest a common mechanism for the processing of time errors

Paced finger tapping is a sensorimotor synchronization task where a subject has to keep pace with a metronome while the time differences (asynchronies) between each stimulus and its response are recorded. A usual way to study the underlying error correction mechanism is to perform unexpected temporal perturbations to the stimuli sequence. An overlooked issue is that at the moment of a temporal perturbation two things change: the stimuli period (a parameter) and the asynchrony (a variable). In terms of experimental manipulation, it would be desirable to have separate, independent control of parameter and variable values. In this work we perform paced finger tapping experiments combining simple temporal perturbations (tempo step change) and spatial perturbations with temporal effect (raised or lowered point of contact). In this way we decouple the parameter-and-variable confounding, performing novel perturbations where either the parameter or the variable changes. Our results show nonlinear features like asymmetry and are compatible with a common error correction mechanism for all types of asynchronies. We suggest taking this confounding into account when analyzing perturbations of any kind in finger tapping tasks but also in other areas of sensorimotor synchronization, like music performance experiments and paced walking in gait coordination studies.

Coordination Elicits Synchronous Brain Activity Between Co-actors: Frequency Ratio Matters

People could behave in two different ways when engaging in interpersonal coordination activities: moving at the same frequency (isofrequency pattern, IP; the movement frequency ratio is 1:1) or at different frequencies (multifrequency pattern, MP; the movement frequency ratio is non 1:1). However, how the interpersonal coordination pattern modulates coordination outcome and the related brain-to-brain connectivity is not fully understood. Here, we adopted a continuous joint drawing task in which two participants co-drew parallelogram shapes according to two coordination patterns (i.e., IP vs. MP) while their brain activities were simultaneously recorded by the functional near-infrared spectroscopy (fNIRS) based hyperscanning technique. Dyads showed better coordination performance, as well as relatively greater interpersonal brain synchronization (IBS) at the left frontopolar area, in the MP condition compared to the IP condition. Granger causality analyses further disclosed the bidirectional influences between the brains of the coordinating individuals. Such interpersonal influences were enhanced when individuals coordinated in the MP condition. Finally, the IBS during coordination was related to the dyadic self-control level. Taken together, our study revealed that interpersonal multifrequency coordination pattern facilitates the coordination efficiency, which was associated with the enhanced brain-to-brain connectivity. Our work also suggests the potentially positive role of self-control during the interpersonal coordination process.

Musical Role Asymmetries in Piano Duet Performance Influence Alpha-Band Neural Oscillation and Behavioral Synchronization

Recent work in interpersonal coordination has revealed that neural oscillations, occurring spontaneously in the human brain, are modulated during the sensory, motor, and cognitive processes involved in interpersonal interactions. In particular, alpha-band (8-12 Hz) activity, linked to attention in general, is related to coordination dynamics and empathy traits. Researchers have also identified an association between each individual's attentiveness to their co-actor and the relative similarity in the co-actors' roles, influencing their behavioral synchronization patterns. We employed music ensemble performance to evaluate patterns of behavioral and neural activity when roles between co-performers are systematically varied with complete counterbalancing. Specifically, we designed a piano duet task, with three types of co-actor dissimilarity, or asymmetry: (1) musical role (starting vs. joining), (2) musical task similarity (similar vs. dissimilar melodic parts), and (3) performer animacy (human-to-human vs. human-to-non-adaptive computer). We examined how the experience of these asymmetries in four initial musical phrases, alternatingly played by the co-performers, influenced the pianists' performance of a subsequent unison phrase. Electroencephalography was recorded simultaneously from both performers while playing keyboards. We evaluated note-onset timing and alpha modulation around the unison phrase. We also investigated whether each individual's self-reported empathy was related to behavioral and neural activity. Our findings revealed closer behavioral synchronization when pianists played with a human vs. computer partner, likely because the computer was non-adaptive. When performers played with a human partner, or a joining performer played with a computer partner, having a similar vs. dissimilar musical part did not have a significant effect on their alpha modulation immediately prior to unison. However, when starting performers played with a computer partner with a dissimilar vs. similar part there was significantly greater alpha synchronization. In other words, starting players attended less to the computer partner playing a similar accompaniment, operating in a solo-like mode. Moreover, this alpha difference based on melodic similarity was related to a difference in note-onset adaptivity, which was in turn correlated with performer trait empathy. Collectively our results extend previous findings by showing that musical ensemble performance gives rise to a socialized context whose lasting effects encompass attentiveness, perceptual-motor coordination, and empathy.

Dynamic Orchestration of Brains and Instruments During Free Guitar Improvisation

Playing music in ensemble requires enhanced sensorimotor coordination and the non-verbal communication of musicians that need to coordinate their actions precisely with those of others. As shown in our previous studies on guitar duets, and also on a guitar quartet, intra- and inter-brain synchronization plays an essential role during such interaction. At the same time, sensorimotor coordination as an essential part of this interaction requires being in sync with the auditory signals coming from the played instruments. In this study, using acoustic recordings of guitar playing and electroencephalographic (EEG) recordings of brain activity from guitarists playing in duet, we aimed to explore whether the musicians' brain activity synchronized with instrument sounds produced during guitar playing. To do so, we established an analytical method based on phase synchronization between time-frequency transformed guitar signals and raw EEG signals. Given phase synchronization, or coupling between guitar and brain signals, we constructed so-called extended hyper-brain networks comprising all possible interactions between two guitars and two brains. Applying a graph-theoretical approach to these networks assessed across time, we present dynamic changes of coupling strengths or dynamic orchestration of brains and instruments during free guitar improvisation for the first time. We also show that these dynamic network topology changes are oscillatory in nature and are characterized by specific spectral peaks, indicating the temporal structure in the synchronization patterns between guitars and brains. Moreover, extended hyper-brain networks exhibit specific modular organization varying in time, and binding each time, different parts of the network into the modules, which were mostly heterogeneous (i.e., comprising signals from different instruments and brains or parts of them). This suggests that the method capturing synchronization between instruments and brains when playing music provides crucial information about the underlying mechanisms. We conclude that this method may be an indispensable tool in the investigation of social interaction, music therapy, and rehabilitation dynamics.

Empathic perspective taking promotes interpersonal coordination through music

Coordinated behavior promotes collaboration among humans. To shed light upon this relationship, we investigated whether and how interpersonal coordination is promoted by empathic perspective taking (EPT). In a joint music-making task, pairs of participants rotated electronic music-boxes, producing two streams of musical sounds that were meant to be played synchronously. Participants – who were not musically trained – were assigned to high and low EPT groups based on pre-experimental assessments using a standardized personality questionnaire. Results indicated that high EPT pairs were generally more accurate in synchronizing their actions. When instructed to lead the interaction, high and low EPT leaders were equally cooperative with followers, making their performance tempo more regular, presumably in order to increase their predictability and help followers to synchronize. Crucially, however, high EPT followers were better able to use this information to predict leaders’ behavior and thus improve interpersonal synchronization. Thus, empathic perspective taking promotes interpersonal coordination by enhancing accuracy in predicting others’ behavior while leaving the aptitude for cooperation unaltered. We argue that such predictive capacity relies on a sensorimotor mechanism responsible for simulating others’ actions in an anticipatory manner, leading to behavioral advantages that may impact social cognition on a broad scale.

Tutorial and simulations with ADAM: an adaptation and anticipation model of sensorimotor synchronization

Interpersonal coordination of movements often involves precise synchronization of action timing, particularly in expert domains such as ensemble music performance. According to the adaptation and anticipation model (ADAM) of sensorimotor synchronization, precise yet flexible interpersonal coordination is supported by reactive error correction mechanisms and anticipatory mechanisms that exploit systematic patterns in stimulus timing to plan future actions. Here, we provide a tutorial introduction to the computational architecture of ADAM and present a series of single- and dual-virtual agent simulations that examine the model parameters that produce ideal synchronization performance in different tempo conditions. In the single-agent simulations, a virtual agent synchronized responses to steady tempo sequence or a sequence containing gradual tempo changes. Parameters controlling basic reactive error (phase) correction were sufficient for producing ideal synchronization performance at the steady tempo, whereas parameters controlling anticipatory mechanisms were necessary for ideal performance with a tempo-changing sequence. In the dual-agent simulations, two interacting virtual agents produced temporal sequences from either congruent or incongruent internal performance templates specifying a steady tempo or tempo changes. Ideal performance was achieved with reactive error correction alone when both agents implemented the same performance template (either steady tempo or tempo change). In contrast, anticipatory mechanisms played a key role when one agent implemented a steady tempo template and the other agent implemented a tempo change template. These findings have implications for understanding the interplay between reactive and anticipatory mechanisms when agents possess compatible versus incompatible representations of task goals during human-human and human-machine interaction.

Developmental Changes in Task-Induced Brain Deactivation in Humans Revealed by a Motor Task

Performing tasks activates relevant brain regions in adults while deactivating task-irrelevant regions. Here, using a well-controlled motor task, we explored how deactivation is shaped during typical human development and whether deactivation is related to task performance. Healthy right-handed children (8-11 years), adolescents (12-15 years), and young adults (20-24 years; 20 per group) underwent functional magnetic resonance imaging with their eyes closed while performing a repetitive button-press task with their right index finger in synchronization with a 1-Hz sound. Deactivation in the ipsilateral sensorimotor cortex (SM1), bilateral visual and auditory (cross-modal) areas, and bilateral default mode network (DMN) progressed with development. Specifically, ipsilateral SM1 and lateral occipital deactivation progressed prominently between childhood and adolescence, while medial occipital (including primary visual) and DMN deactivation progressed from adolescence to adulthood. In adults, greater cross-modal deactivation in the bilateral primary visual cortices was associated with higher button-press timing accuracy relative to the sound. The region-specific deactivation progression in a developmental period may underlie the gradual promotion of sensorimotor function segregation required in the task. Task-induced deactivation might have physiological significance regarding suppressed activity in task-irrelevant regions. Furthermore, cross-modal deactivation develops to benefit some aspects of task performance in adults.

Audio cues enhance mirroring of arm motion when visual cues are scarce

Swing in a crew boat, a good jazz riff, a fluid conversation: these tasks require extracting sensory information about how others flow in order to mimic and respond. To determine what factors influence coordination, we build an environment to manipulate incoming sensory information by combining virtual reality and motion capture. We study how people mirror the motion of a human avatar's arm as we occlude the avatar. We efficiently map the transition from successful mirroring to failure using Gaussian process regression. Then, we determine the change in behaviour when we introduce audio cues with a frequency proportional to the speed of the avatar's hand or train individuals with a practice session. Remarkably, audio cues extend the range of successful mirroring to regimes where visual information is sparse. Such cues could facilitate joint coordination when navigating visually occluded environments, improve reaction speed in human-computer interfaces or measure altered physiological states and disease.

Cross-feedback with Partner Contributes to Performance Accuracy in Finger-tapping Rhythm Synchronization between One Leader and Two Followers

As observed in musical ensembles, people synchronize with a leader together with other people. This study aimed to investigate whether interdependency with a partner improves performance accuracy in rhythm synchronization with the leader. Participants performed a synchronization task via auditory signal by finger tapping in which two followers simultaneously synchronized with a leader: an isochronous metronome or a human leader with or without feedback from the followers. This task was conducted with and without cross-feedback (CFB) between the followers. The followers’ weak mutual tempo tracking via the CFB and the followers’ strong tempo tracking to the leader improved the tempo stability. Additionally, because the interdependency between the followers was weaker than the followers’ dependency on the human leader, the CFB did not enlarge the synchronization error between the human leader and the followers, which occurred in synchronization with the metronome. Thus, the CFB between the followers contributed to accuracy in synchronization with the human leader. The results suggest that in ensembles, players should strongly attend to the leader and should attempt to be less conscious of partners to maintain the appropriate balance between influences from the leader and partners.

Ears, heads, and eyes: When singers synchronise

We examined the relationship between endogenous rhythms, auditory and visual cues, and body movement in the temporal coordination of duet singers. Sixteen pairs of experienced vocalists sang a familiar melody in Solo and two Duet conditions. Vocalists sang together in Unison (simultaneously producing identical pitches) and Round Duet conditions (one vocalist, the Follower, producing pitches at an eight-tone delay from their partner, the Leader) while facing Inward (full visual cues) and Outward (reduced visual cues). Larger tempo differences in partners' spontaneous (temporally unconstrained) Solo performances were associated with larger asynchrony in Duet performances, consistent with coupling predictions for oscillators with similar natural frequencies. Vocalists were slightly but consistently more synchronous in Duets when facing their partner (Inward) than when facing Outward; Unison and Round performances were equally synchronous. The greater difficulty of Rounds production was evidenced in vocalists' slower performance rates and more variable head movements; Followers directed their head gaze away from their partner and used bobbing head movements to mark the musical beat. The strength of Followers' head movements corresponded to the amount of tone onset asynchrony with their partners, indicating a strong association between timing and movement under increased attentional and working memory demands in music performance.

The roles of musical expertise and sensory feedback in beat keeping and joint action

Auditory feedback of actions provides additional information about the timing of one’s own actions and those of others. However, little is known about how musicians and nonmusicians integrate auditory feedback from multiple sources to regulate their own timing or to (intentionally or unintentionally) coordinate with a partner. We examined how musical expertise modulates the role of auditory feedback in a two-person synchronization–continuation tapping task. Pairs of individuals were instructed to tap at a rate indicated by an initial metronome cue in all four auditory feedback conditions: no feedback, self-feedback (cannot hear their partner), other feedback (cannot hear themselves), or full feedback (both self and other). Participants within a pair were either both musically trained (musicians), both untrained (nonmusicians), or one musically trained and one untrained (mixed). Results demonstrated that all three pair types spontaneously synchronized with their partner when receiving other or full feedback. Moreover, all pair types were better at maintaining the metronome rate with self-feedback than with no feedback. Musician pairs better maintained the metronome rate when receiving other feedback than when receiving no feedback; in contrast, nonmusician pairs were worse when receiving other or full feedback compared to no feedback. Both members of mixed pairs maintained the metronome rate better in the other and full feedback conditions than in the no feedback condition, similar to musician pairs. Overall, nonmusicians benefited from musicians’ expertise without negatively influencing musicians’ ability to maintain the tapping rate. One implication is that nonmusicians may improve their beat-keeping abilities by performing tasks with musically skilled individuals.

fNIRS Responses in Professional Violinists While Playing Duets: Evidence for Distinct Leader and Follower Roles at the Brain Level

Music played in ensembles is a naturalistic model to study joint action and leader-follower relationships. Recently, the investigation of the brain underpinnings of joint musical actions has gained attention; however, the cerebral correlates underlying the roles of leader and follower in music performance remain elusive. The present study addressed this question by simultaneously measuring the hemodynamic correlates of functional neural activity elicited during naturalistic violin duet performance using fNIRS. Findings revealed distinct patterns of functional brain activation when musicians played the Violin 2 (follower) than the Violin 1 part (leader) in duets, both compared to solo performance. More specifically, results indicated that musicians playing the Violin 2 part had greater oxy-Hb activation in temporo-parietal (p = 0.02) and somatomotor (p = 0.04) regions during the duo condition in relation to the solo. On the other hand, there were no significant differences in the activation of these areas between duo/solo conditions during the execution of the Violin 1 part (p's > 0.05). These findings suggest that ensemble cohesion during a musical performance may impose particular demands when musicians play the follower position, especially in brain areas associated with the processing of dynamic social information and motor simulation. This study is the first to use fNIRS hyperscanning technology to simultaneously measure the brain activity of two musicians during naturalistic music ensemble performance, opening new avenues for the investigation of brain correlates underlying joint musical actions with multiple subjects in a naturalistic environment.

Holistic cognitive and neural processes: a fNIRS-hyperscanning study on interpersonal sensorimotor synchronization

Interpersonal sensorimotor synchronization (interpersonal SMS) is the foundation of complex human social interaction. Previous studies primarily focused on the individual cognitive processes of interpersonal SMS. However, all individuals compose an entire interaction system with emerged holistic properties during interpersonal SMS. Therefore, we proposed the `holistic cognitive and neural processes' of interpersonal SMS and defined quantitative measurements that included Holistic Correction Gain (HCG), Holistic Timekeeper Variance (HTV) and Holistic Motor Variance (HMV) based on linear error correction model and inter-brain couplings obtained by hyperscanning technique. We performed a joint-tapping experiment including bidirectional and unidirectional conditions using functional near-infrared spectroscopy (fNIRS) hyperscanning to evaluate effects of these holistic processes on synchronization performance. We found that the dyads' performance highly correlated with the integrated effect of holistic cognitive processes in both conditions. Each holistic cognitive process played different roles in interpersonal SMS. HCG was critical to maintain synchronization. HTV related to mentalizing others' behavior. Holistic neural process, the inter-brain coupling of right prefrontal cortex (PFC), was significantly different between bidirectional and unidirectional conditions, which suggested the existence of neural markers at holistic level in interpersonal SMS.

The influence of visual cues on temporal anticipation and movement synchronization with musical sequences

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.

Intentionality of a co-actor influences sensorimotor synchronisation with a virtual partner

Interpersonal sensorimotor synchronisation requires individuals to anticipate and adapt to their partner's movement timing. Research has demonstrated that the intentionality of a co-actor affects joint action planning, however, less is known about whether co-actor intentionality affects sensorimotor synchronisation. Explicit and implicit knowledge of a synchronisation partner's intentionality may influence coordination by modulating temporal anticipation and adaptation processes. We used a computer-controlled virtual partner (VP) consisting of tempo-changing auditory pacing sequences to simulate either an intentional or unintentional synchronisation partner. The VP was programmed to respond to the participant with low or moderate degrees of error correction, simulating a slightly or moderately adaptive human, respectively. In addition, task instructions were manipulated so that participants were told they were synchronising with either another person or a computer. Results indicated that synchronisation performance improved with the more adaptive VP. In addition, there was an influence of the explicit partner instruction, but this was dependent upon the degree of VP adaptivity and was modulated by subjective preferences for either the human or the computer partner. Beliefs about the intentionality of a synchronisation partner may thus influence interpersonal sensorimotor synchronisation in a manner that is modulated by preferences for interacting with intentional agents.

Sensory-motor synchronization in the brain corresponds to behavioral synchronization between individuals

Behavioral rhythms between individuals are known to spontaneously synchronize through social interactions; however, it remains unclear whether inter-brain synchronization emerges with this behavioral synchronization in the case of anti-phase coordination with other's behavior (e.g. turn-taking). In this study, we simultaneously recorded electroencephalograms (EEGs) we simultaneously recorded electroencephalograms (EEGs) from 2 participants as 1 pair (in total, 34 right-handed participants as 17 pairs) during an alternate tapping task in which pairs of participants alternated tapping a key with their right finger. Participants sat facing computer displays and were asked to match their partners' tapping intervals using visual feedback that was presented on the displays. Based on their ability to synchronize, we divided participants into Good performance and Poor performance groups. In both groups, wavelet analyses of EEG data revealed alpha-(approximately 12 Hz) and beta-(approximately 20 Hz) amplitude modulation in the left motor areas. Interestingly, both alpha and beta amplitudes were correlated between individuals from the Good group, but not from the Poor group. Moreover, while the Good group showed intra-brain and inter-brain alpha-phase synchronization (about 12 Hz) within the posterior brain areas (i.e., visual areas) and the central brain areas (i.e., motor areas), the Poor group did not. These results suggest that inter-brain synchronization may play an important role in coordinating one's behavioral rhythms with those of others.

Joint action coordination in expert-novice pairs: Can experts predict novices' suboptimal timing?

Previous research has established that skilled joint action partners use predictive models to achieve temporal coordination, for instance, when playing a music duet. But how do joint action partners with different skill levels achieve coordination? Can experts predict the suboptimal timing of novices? What kind of information allows them to predict novices’ timing? To address these questions, we asked skilled pianists to perform duets with piano novices. We varied whether, prior to performing duets, experts were familiar with novices’ performances of their individual parts of the duets and whether experts had access to the musical scores including the novices’ part of the duet. Familiarity with the score led to better coordination when the score implied a difficult passage. Familiarity with novices’ performances led to better joint action coordination for the remaining parts of the duet. Together, the results indicate that experts are surprisingly flexible in predicting novices’ suboptimal timing.

Predictive rhythmic tapping to isochronous and tempo changing metronomes in the nonhuman primate

Beat entrainment is the ability to entrain one's movements to a perceived periodic stimulus, such as a metronome or a pulse in music. Humans have a capacity to predictively respond to a periodic pulse and to dynamically adjust their movement timing to match the varying music tempos. Previous studies have shown that monkeys share some of the human capabilities for rhythmic entrainment, such as tapping regularly at the period of isochronous stimuli. However, it is still unknown whether monkeys can predictively entrain to dynamic tempo changes like humans. To address this question, we trained monkeys in three tapping tasks and compared their rhythmic entrainment abilities with those of humans. We found that, when immediate feedback about the timing of each movement is provided, monkeys can predictively entrain to an isochronous beat, generating tapping movements in anticipation of the metronome pulse. This ability also generalized to a novel untrained tempo. Notably, macaques can modify their tapping tempo by predicting the beat changes of accelerating and decelerating visual metronomes in a manner similar to humans. Our findings support the notion that nonhuman primates share with humans the ability of temporal anticipation during tapping to isochronous and smoothly changing sequences of stimuli.