Mean Asynchrony Research Articles

The effect of rhythmic stimuli with spatial information on sensorimotor synchronization: an EEG and EMG study.

Sensorimotor synchronization (SMS) is the human ability to align body movement rhythms with external rhythmic stimuli. While the effects of rhythmic stimuli containing only temporal information on SMS have been extensively studied, less is known about how spatial information affects SMS performance. This study investigates the neural mechanisms underlying SMS with rhythmic stimuli that include both temporal and spatial information, providing insights into the influence of these factors across different sensory modalities. This study compared the effects temporal information and spatial information on SMS performance across different stimuli conditions. We simultaneously recorded the electroencephalogram (EEG), the electromyogram (EMG), and behavioral data as subjects performed synchronized tapping to rhythmic stimuli. The study analyzed SMS performance under conditions including auditory, visual, and auditory-visual motion stimuli (containing both temporal and spatial information), as well as auditory, visual, and auditory-visual non-motion stimuli (containing only temporal information). Specifically, the research examined behavioral data (i.e., mean asynchrony, absolute asynchrony, and variability), neural oscillations, cortico-muscular coherence (CMC), and brain connectivity. The results demonstrated that SMS performance was superior with rhythmic stimuli containing both temporal and spatial information compared to stimuli with only temporal information. Moreover, sensory-motor neural entrainment was stronger during SMS with rhythmic stimuli containing spatial information within the same sensory modality. SMS with both types of rhythmic stimuli was found to be dynamically modulated by neural oscillations and cortical-muscular coupling in the beta band (13-30 Hz). These findings provide deeper insights into the combined effects of temporal and spatial information, as well as sensory modality, on SMS performance. The study highlights the dynamic modulation of SMS by neural oscillations and CMC, particularly in the beta band, offering valuable contributions to understanding the neural basis of sensorimotor synchronization.

Neurologically Motivated Simulation of Ensemble Performance

A “rhythmic agent” is simulated based on the foundation of a previously published behavioral sensorimotor synchronization (SMS) model. The model is adjustable to control the auditory and tactile modalities of the tap's feedback. In addition to the conventional mechanisms of phase and period error correction, as well as their activation conditions, the period is estimated by modeling a central timekeeper impacted by a novel short-term memory. Inspired by The ADaptation and Anticipation Model (ADAM), a mechanism for linearly extrapolating anticipation is also tested. To better match the perceptual and motor cognitive functions, the model's parameters have been tuned to observations from experimental neurosensory literature with an emphasis on transduction delays. The agent is programmed to synchronize with various external rhythmic input signals while accounting for both adaptive and predictive mechanisms. The definition of the agent is based on a minimal set of rules yet has successfully replicated results of real-world observations: against a metronome; it produces the well-known negative mean asynchrony. In a rhythmic joint action, the simulation of joint delayed coordination shows a behavior previously observed in human subjects: in a rhythmic collaboration, a moderate amount of delay is necessary to keep the tempo steady, and below that threshold, the rhythm tends to speed up. It is also shown that giving more weight to the tactile afferent feedback than the auditory intensifies this effect. Moreover, it is observed that including anticipation in addition to the reactive mechanism will decrease the effect. The proposed model as a rhythmic engine, combined with other standard modules such as a beat detection algorithm, can be used to implement musical co-performers that could improvise with a human rhythmically or perform a given score in a way that feels human-like.

Impact on the ability of healthcare professionals to correctly identify patient-ventilator asynchronies of the simultaneous visualization of estimated muscle pressure curves on the ventilator display: a randomized study (Pmus study)

BackgroundPatient-ventilator asynchronies are usually detected by visual inspection of ventilator waveforms but with low sensitivity, even when performed by experts in the field. Recently, estimation of the inspiratory muscle pressure (Pmus) waveforms through artificial intelligence algorithm has been proposed (Magnamed®, São Paulo, Brazil). We hypothesized that the display of these waveforms could help healthcare providers identify patient-ventilator asynchronies.MethodsA prospective single-center randomized study with parallel assignment was conducted to assess whether the display of the estimated Pmus waveform would improve the correct identification of asynchronies in simulated clinical scenarios. The primary outcome was the mean asynchrony detection rate (sensitivity). Physicians and respiratory therapists who work in intensive care units were randomized to control or intervention group. In both groups, participants analyzed pressure and flow waveforms of 49 different scenarios elaborated using the ASL-5000 lung simulator. In the intervention group the estimated Pmus waveform was displayed in addition to pressure and flow waveforms.ResultsA total of 98 participants were included, 49 per group. The sensitivity per participant in identifying asynchronies was significantly higher in the Pmus group (65.8 ± 16.2 vs. 52.94 ± 8.42, p < 0.001). This effect remained when stratifying asynchronies by type.ConclusionsWe showed that the display of the Pmus waveform improved the ability of healthcare professionals to recognize patient-ventilator asynchronies by visual inspection of ventilator tracings. These findings require clinical validation.Trial registration: ClinicalTrials.gov: NTC05144607. Retrospectively registered 3 December 2021.

Synchronization during Improvised Active Music Therapy in clients with Parkinson’s disease

ABSTRACT Introduction The purpose of this manuscript is to report on the finding of asynchrony measures during Improvised Active Music Therapy (IAMT) sessions with individuals with Parkinson’s disease (PD). Method In this single subject multiple baseline design across subjects, the study measured asynchrony of three right-handed participants with PD while playing uninterrupted improvised music on a simplified electronic drum-set. During baseline, the music therapist played rhythms with lowto moderate density of syncopation. During treatment, the music therapist introduced rhythms with moderate to high density of syncopation. The music content of the sessions was transformed into digital music using Musical Instrument Digital Interface (MIDI). MIDI data were analyzed to determine participants’ and the music therapist’s asynchrony (on acoustic guitar) during baseline and treatment conditions. Results The results of this manuscript suggest that all participants exhibited total negative mean asynchrony and in that the music therapist exhibited total positive mean asynchrony scores within and across conditions. All participants also demonstrated score fluctuation in left foot and right foot as compared to upper extremity within and across conditions. Discussion Overall, participants showed their ability to synchronize to the music produced by the music therapist throughout conditions by demonstrating anticipation. Also, participants demonstrated some difficulty while synchronizing with lower extremity. Music therapy clinicians might benefit from knowledge of their own tempo inconsistencies to be able to synchronize with clients more effectively. More research is required to identify commonalities and differences in music synchronization measures between individuals with PD and healthy individuals during IAMT sessions.

White matter correlates of sensorimotor synchronization in persistent developmental stuttering

IntroductionIndividuals with persistent developmental stuttering display deficits in aligning motor actions to external cues (i.e., sensorimotor synchronization). Diffusion imaging studies point to stuttering-associated differences in dorsal, not ventral, white matter pathways, and in the cerebellar peduncles. Here, we studied microstructural white matter differences between adults who stutter (AWS) and fluent speakers using two complementary approaches to: (a) assess previously reported group differences in white matter diffusivity, and (b) evaluate the relationship between white matter diffusivity and sensorimotor synchronization in each group. MethodsParticipants completed a sensorimotor synchronization task and a diffusion MRI scan. We identified the cerebellar peduncles and major dorsal- and ventral-stream language pathways in each individual and assessed correlations between sensorimotor synchronization and diffusion measures along the tracts. ResultsThe results demonstrated group differences in dorsal, not ventral, language tracts, in alignment with prior reports. Specifically, AWS had significantly lower fractional anisotropy (FA) in the left arcuate fasciculus, and significantly higher mean diffusivity (MD) in the bilateral frontal aslant tract compared to fluent speakers, while no significant group difference was detected in the inferior fronto-occipital fasciculus. We also found significant group differences in both FA and MD of the left middle cerebellar peduncle. Comparing patterns of association with sensorimotor synchronization revealed a novel double dissociation: MD within the left inferior cerebellar peduncle was significantly correlated with mean asynchrony in AWS but not in fluent speakers, while FA within the left arcuate fasciculus was significantly correlated with mean asynchrony in fluent speakers, but not in AWS. ConclusionsOur results support the view that stuttering involves altered connectivity in dorsal tracts and that AWS may rely more heavily on cerebellar tracts to process timing information. Evaluating microstructural associations with sensitive behavioral measures provides a powerful tool for discovering additional functional differences in the underlying connectivity in AWS.

Neural Entrainment Meets Behavior: The Stability Index as a Neural Outcome Measure of Auditory-Motor Coupling.

Understanding rhythmic behavior in the context of coupled auditory and motor systems has been of interest to neurological rehabilitation, in particular, to facilitate walking. Recent work based on behavioral measures revealed an entrainment effect of auditory rhythms on motor rhythms. In this study, we propose a method to compute the neural component of such a process from an electroencephalographic (EEG) signal. A simple auditory-motor synchronization paradigm was used, where 28 healthy participants were instructed to synchronize their finger-tapping with a metronome. The computation of the neural outcome measure was carried out in two blocks. In the first block, we used Generalized Eigendecomposition (GED) to reduce the data dimensionality to the component which maximally entrained to the metronome frequency. The scalp topography pointed at brain activity over contralateral sensorimotor regions. In the second block, we computed instantaneous frequency from the analytic signal of the extracted component. This returned a time-varying measure of frequency fluctuations, whose standard deviation provided our “stability index” as a neural outcome measure of auditory-motor coupling. Finally, the proposed neural measure was validated by conducting a correlation analysis with a set of behavioral outcomes from the synchronization task: resultant vector length, relative phase angle, mean asynchrony, and tempo matching. Significant moderate negative correlations were found with the first three measures, suggesting that the stability index provided a quantifiable neural outcome measure of entrainment, with selectivity towards phase-correction mechanisms. We address further adoption of the proposed approach, especially with populations where sensorimotor abilities are compromised by an underlying pathological condition. The impact of using stability index can potentially be used as an outcome measure to assess rehabilitation protocols, and possibly provide further insight into neuropathological models of auditory-motor coupling.

Timing Is Everything…Or Is It? Effects of Instructed Timing Style, Reference, and Pattern on Drum Kit Sound in Groove-Based Performance

This study reports on an experiment that tested whether drummers systematically manipulated not only onset but also duration and/or intensity of strokes in order to achieve different timing styles. Twenty-two professional drummers performed two patterns (a simple “back-beat” and a complex variation) on a drum kit (hi-hat, snare, kick) in three different timing styles (laid-back, pushed, on-beat), in tandem with two timing references (metronome and instrumental backing track). As expected, onset location corresponded to the instructed timing styles for all instruments. The instrumental reference led to more pronounced timing profiles than the metronome (pushed strokes earlier, laid-back strokes later). Also, overall the metronome reference led to earlier mean onsets than the instrumental reference, possibly related to the “negative mean asynchrony” phenomenon. Regarding sound, results revealed systematic differences across participants in the duration (snare) and intensity (snare and hi-hat) of strokes played using the different timing styles. Pattern also had an impact: drummers generally played the rhythmically more complex pattern 2 louder than the simpler pattern 1 (snare and kick). Overall, our results lend further evidence to the hypothesis that both temporal and sound-related features contribute to the indication of the timing of a rhythmic event in groove-based performance.

Outcomes of ventilatory asynchrony in patients with inspiratory effort.

ObjectiveTo identify the relationship of patient-ventilator asynchrony with the level of sedation and hemogasometric and clinical results.MethodsThis was a prospective study of 122 patients admitted to the intensive care unit who underwent > 24 hours of invasive mechanical ventilation with inspiratory effort. In the first 7 days of ventilation, patient-ventilator asynchrony was evaluated daily for 30 minutes. Severe patient-ventilator asynchrony was defined as an asynchrony index > 10%.ResultsA total of 339,652 respiratory cycles were evaluated in 504 observations. The mean asynchrony index was 37.8% (standard deviation 14.1 - 61.5%). The prevalence of severe patient-ventilator asynchrony was 46.6%. The most frequent patient-ventilator asynchronies were ineffective trigger (13.3%), autotrigger (15.3%), insufficient flow (13.5%), and delayed cycling (13.7%). Severe patient-ventilator asynchrony was related to the level of sedation (ineffective trigger: p = 0.020; insufficient flow: p = 0.016; premature cycling: p = 0.023) and the use of midazolam (p = 0.020). Severe patient-ventilator asynchrony was also associated with hemogasometric changes. The persistence of severe patient-ventilator asynchrony was an independent risk factor for failure of the spontaneous breathing test, ventilation time, ventilator-associated pneumonia, organ dysfunction, mortality in the intensive care unit, and length of stay in the intensive care unit.ConclusionPatient-ventilator asynchrony is a frequent disorder in critically ill patients with inspiratory effort. The patient’s interaction with the ventilator should be optimized to improve hemogasometric parameters and clinical results. Further studies are required to confirm these results.

Development of Adapted Guitar to Improve Motor Function After Stroke: Feasibility Study in Young Adults.

Recent research indicates that music-supported therapies may offer unique benefits for rehabilitation of motor function after stroke. We designed an adapted guitar and training task aimed to improve coordination between rhythmic and discrete movements because individuals recovering from stroke have greater difficulty performing discrete vs. rhythmic movements. In this paper, we report a feasibility study on training to play this adapted guitar in healthy young adults. Subjects (N = 10) practiced two rhythmic strumming patterns over three consecutive days using their non-dominant hand guided by an audiovisual metronome (60 bpm). They were also instructed to press a foot pedal while maintaining the strumming movement. Elbow and wrist kinematics were estimated using wireless inertial measurement units. Results showed positive mean asynchrony between strum onsets and metronome onsets, and a decrease in the standard deviation of mean asynchrony over practice. In early practice, participants slowed the strumming movement when they pressed the foot pedal, but this interference decreased on days two and three. Smoothness of the elbow movement during the strum phase, which includes the contact with the strings, increased over practice, while smoothness of the return phase did not change over practice. The predominant joint coordination pattern used for the strum phase consisted of elbow extension coupled with elbow pronation, wrist extension, and ulnar deviation. We discuss how these results fit into current music-based rehabilitation literature and outline directions for future applications of this music-supported intervention.

Adults who stutter and metronome synchronization: evidence for a nonspeech timing deficit.

Speech timing deficits have been proposed as a causal factor in the disorder of stuttering. The question of whether individuals who stutter have deficits in nonspeech timing is one that has been revisited often, with conflicting results. Here, we uncover subtle differences in a manual metronome synchronization task that included tempo changes with adults who stutter and fluent speakers. We used sensitive circular statistics to examine both asynchrony and consistency in motor production. While both groups displayed a classic negative mean asynchrony (tapping before the beat), individuals who stutter anticipated the beat even more than their fluent peers, and their consistency was particularly affected at slow tempi. Surprisingly, individuals who stutter did not have problems with interval correction at tempo changes. We also examined the influence of music experience on synchronization behavior in both groups. While music perception and training were related to synchronization behavior in fluent participants, these correlations were not present for the stuttering group; however, one measure of stuttering severity (self-rated severity) was negatively correlated with music training. Overall, we found subtle differences in paced auditory-motor synchronization in individuals who stutter, consistent with a timing problem extending to nonspeech.

Does dance training influence beat sensorimotor synchronization? Differences in finger-tapping sensorimotor synchronization between competitive ballroom dancers and nondancers.

Sensorimotor synchronization is the coordination of rhythmic movement with an external beat. Dancers often synchronize each beat of their motion with an external rhythm. Compared with social dancing, competitive ballroom dancing requires a higher level of sensorimotor ability. Although previous studies have found that dance experience may facilitate sensorimotor synchronization, they did not examine this in competitive ballroom dancers. Thus, the present study compared sensorimotor synchronization in 41 nondancers and 41 skilled, competitive ballroom dancers as they performed a simple beat synchronization finger-tapping task. All participants finger-tapped freely at their preferred tempo before the formal experiments. Participants were then required to synchronize their finger-tapping with auditory, visual, or combined audiovisual signals in separate experiments and at varying tempos. To assess sensorimotor plasticity, the participants then repeated the free-tapping task after completing all three finger-tapping experiments. Compared with nondancers, dancers showed more accurate and stable beat synchronization. Dancers tapped before onset of all three types of sensorimotor stimulation, indicating a significant negative mean asynchrony and had a tendency to anticipate (predict) the stimuli. Dancers tended to auditory stimulation for beat sensorimotor synchronization, whereas nondancers tended to visual stimuli. Dancers had a faster tempo preference in the initial free-tapping task; however, the preferred tapping tempo increased in all participants in the second free-tapping task, suggesting that beat induction is affected by practice. Together these findings suggest that dance experience enhances sensorimotor synchronization and sensorimotor plasticity, with ballroom dancers tending to auditory stimulation for beat induction.

Optimizing beat synchronized running to music.

The use of music and specifically tempo-matched music has been shown to affect running performance. But can we maximize the synchronization of movements to music and does maximum synchronization influence kinematics and motivation? In this study, we explore the effect of different types of music-to-movement alignment strategies on phase coherence, cadence and motivation. These strategies were compared to a control condition where the music tempo was deliberately not aligned to the running cadence. Results show that without relative phase alignment, a negative mean asynchrony (NMA) of footfall timings with respect to the beats is obtained. This means that footfalls occurred slightly before the beat and that beats were anticipated. Convergence towards this NMA or preferred relative phase angle was facilitated when the first music beat of a new song started close to the step, which means that entrainment occurred. The results also show that using tempo and phase alignment, the relative phase can be manipulated or forced in a certain angle with a high degree of accuracy. Ensuring negative angles larger than NMA (step before beat) results in increased motivation and decreasing cadence. Running in NMA or preferred relative phase angles results in a null effect on cadence. Ensuring a positive phase angle with respect to NMA results in higher motivation and higher cadence. None of the manipulations resulted in change in perceived exhaustion or a change in velocity. Results also indicate that gender plays an important role when using forced phase algorithms: effects were more pronounced for the female population than for the male population. The implementation of the proposed alignment strategies and control of beat timing while running opens possibilities optimizing the individual running cadence and motivation.

Musical stimulation with feedback in gait training for Parkinson’s disease.

Patients suffering from idiopathic Parkinson's disease (PD) are unable to steadily generate regular steps due to an impairment of the basal ganglia that do not cue the supplementary motor area properly (Iansek, Bradshaw, Phillips, Cunnington, & Morris, 1995). This results in the main hallmarks of parkinsonian gait: reduced step cadence, reduced velocity, and shortened stride length. In the 1990s the use of acoustic stimulation for the rehabilitation of gait disorders in PD was developed under the concept of rhythmic auditory stimulation (RAS). RAS consists of a clear accentuated, either metronomic or musical rhythm that stimulates the production of rhythmical movements (Thaut, 2005), especially with respect to their timing. The consistent coupling between steady tempo of the acoustic stimulation (bpm, beats per minute) and walking cadence (spm, steps per minute) of PD patients has This been systematically investigated and the effectiveness of RAS broadly attested (for reviews see Lim et al., 2005; Nombela, Hughes, Owen, & Grahn, 2013; Tomlinson et al., 2013).In the standard RAS protocol, stimulation tempo usually corresponds to baseline cadence increased by 10% (Arias & Cudeiro, 2008; Freedland et al., 2002; Hausdorff, Lownthal, Herman, Gruendlinger, Peretz, & Giladi, 2007; Willems et al., 2006). RAS exerts a direct effect upon cadence and a consequent effect upon stride length. Because stride length in PD patients is lower than in healthy people at any given velocity (Ebersbach et al., 1999), it may be beneficial for the patient to address it specifically, as an independent therapy goal.Our choice of using musical instead of metronomic stimuli follows music therapist Michael Thaut's approach, where rhythmic stimuli are embedded in a musical structure. The approach is based on findings that rhythmic patterns within a musical context reduce response variability and synchronization offset more effectively than do single-pulse pattern in the frequency range of 60 to 120 spm (Thaut et al., 1996). Moreover, it has been demonstrated that healthy subjects synchronize more precisely (i.e., with lower negative mean asynchrony) with musical rather than metronomic stimuli (Repp, 2005). In the early studies with PD patients, RAS consisted of instrumental pieces in 2/4 or 4/4 m with rhythmic on-beats enhanced by a metronome (McIntosh, Brown, Rice, & Thaut, 1997; Miller, Thaut, McIntosh, & Rice, 1996; Thaut et al., 1996), and it was suggested that, compared with metronome, musical texture provides additional timing information and may therefore facilitate detection, anticipation, and synchronization to the beat (Thaut, Rathbun, & Miller, 1997). Moreover, music facilitates emotional involvement and motivates engagement in a task, and might therefore be a more efficient stimulation than the plain metronome beat. Recently, attention to the comparison between metronomic and musical stimulation and to the specific features that would account for the effectiveness of music seems to be increasing (Buhmann, Desmet, Moens, Van Dyck, & Leman, 2016; Styns, van Noorden, Moelants, & Leman, 2007; Wittwer, Webster, & Hill, 2013). Moreover, the specific effectiveness of music-based movement therapy on PD has been investigated in a meta-analysis (de Dreu, van der Wilk, Poppe, Kwakkel, & van Wegen, 2012).The fundamental advantage of the RAS approach is that it is able to replace the impaired internal stimuli of a parkinsonian brain. However, as stimulation proceeds independently from movement execution, there is no feedback mechanism that helps evaluate movements' adequacy. The potential of concurrent sensory feedback for enhancing motor learning has been extensively studied on healthy subjects (Sigrist, Rauter, Riener, & Wolf, 2013) and an interactive, feedback-like version of RAS has been recently proposed for the training of stride time in PD patients (Hove1, Suzuki, Uchitomi, Orimo, & Miyake, 2012). …

Atypical non-verbal sensorimotor synchronization in adults who stutter may be modulated by auditory feedback

PurposeTo investigate if non-verbal sensorimotor synchronization abilities in adult individuals who stutter (IWS) differ from non-stuttering controls (NS) under various performance conditions (tempo, auditory feedback, use of hands [single/both] and rhythm). MethodsParticipants were 11 IWS (5 males, 6 females, Mean age = 25.8, SD = 8.7) and 11 age- and gender-matched controls (Mean age = 24.4, SD = 8.4). During the experiment, participants were asked to prepare three melodies and subsequently perform them with a metronome at different rates and auditory feedback modalities (non-altered and suppressed). For each task/condition we tracked timing asynchrony related to the steady metronome beat. Results and conclusionsOverall, IWS displayed significantly higher timing asynchrony. Of all conditions, auditory-feedback distinguished IWS from NS most strongly, a subgroup of IWS significantly benefitting from the absence of auditory feedback. In addition, IWS showed a non-significant trend of higher negative mean asynchrony (NMA) and were more affected by the slower rate and increased rhythmic complexity and occasionally suggested poorer beat perception. These results suggest aberrant timing of sensorimotor network interaction associated with the origin of developmental stuttering.

Where is the beat?

The ability to find the beat in a sequence of auditory events may be linked to the ability to learn vocal communication, raising the question of how beat structure in speech events relates to that in other event sequences. We conducted a series of entrainment experiments designed to compare spoken syllable repetition with tapping. Producing taps to a periodic string of auditorily-presented spoken /pa/ syllables resulted in the tap falling between the release burst for the /p/ and the onset of voicing for the vowel. This is consistent with participants intending to align their taps with the vowel onsets but exhibiting the well-documented Negative Mean Asynchrony (NMA) effect, such that the taps precede their “target.” The finding of alignment with the voicing onset is reminiscent of a large body of work on the P-center in repeated spoken syllables. In contrast, producing repeated utterances of the syllable /pa/ to an auditorily-presented click train resulted in coincident occurrence of the release burst with the click, putting the voicing onset after the stimulus (inconsistent with a voicing-onset target with associated NMA). These findings indicate that the location of the beat may differ across tasks involving speech perception and various types of speech production.

White matter microstructural properties correlate with sensorimotor synchronization abilities

Sensorimotor synchronization (SMS) to an external auditory rhythm is a developed ability in humans, particularly evident in dancing and singing. This ability is typically measured in the lab via a simple task of finger tapping to an auditory beat. While simplistic, there is some evidence that poor performance on this task could be related to impaired phonological and reading abilities in children. Auditory-motor synchronization is hypothesized to rely on a tight coupling between auditory and motor neural systems, but the specific pathways that mediate this coupling have not been identified yet. In this study, we test this hypothesis and examine the contribution of fronto-temporal and callosal connections to specific measures of rhythmic synchronization. Twenty participants went through SMS and diffusion magnetic resonance imaging (dMRI) measurements. We quantified the mean asynchrony between an auditory beat and participants' finger taps, as well as the time to resynchronize (TTR) with an altered meter, and examined the correlations between these behavioral measures and diffusivity in a small set of predefined pathways. We found significant correlations between asynchrony and fractional anisotropy (FA) in the left (but not right) arcuate fasciculus and in the temporal segment of the corpus callosum. On the other hand, TTR correlated with FA in the precentral segment of the callosum. To our knowledge, this is the first demonstration that relates these particular white matter tracts with performance on an auditory-motor rhythmic synchronization task. We propose that left fronto-temporal and temporal-callosal fibers are involved in prediction and constant comparison between auditory inputs and motor commands, while inter-hemispheric connections between the motor/premotor cortices contribute to successful resynchronization of motor responses with a new external rhythm, perhaps via inhibition of tapping to the previous rhythm. Our results indicate that auditory-motor synchronization skills are associated with anatomical pathways that have been previously related to phonological awareness, thus offering a possible anatomical basis for the behavioral covariance between these abilities.

Is there a link between sensorimotor coordination and inter-manual coordination? Differential effects of auditory and/or visual rhythmic stimulations.

The purpose of this study was to test how the sensory modality of rhythmic stimuli affects the production of bimanual coordination patterns. To this aim, participants had to synchronize the taps of their two index fingers with auditory and visual stimuli presented separately (auditory or visual) or simultaneously (audio-visual). This kind of task requires two levels of coordination: (1) sensorimotor coordination, which can be measured by the mean asynchrony between the beat of the stimulus and the corresponding tap and by mean asynchrony stability, and (2) inter-manual coordination, which can be assessed by the accuracy and stability of the relative phase between the right-hand and left-hand taps. Previous studies show that sensorimotor coordination is better during the synchronization with auditory or audio-visual metronomes than with visual metronome, but it is not known whether inter-manual coordination is affected by stimulation modalities. To answer this question, 13 participants were required to tap their index fingers in synchrony with the beat of auditory and/or visual stimuli specifying three coordination patterns: two preferred inphase and antiphase patterns and a non-preferred intermediate pattern. A first main result demonstrated that inphase tapping had the best inter-manual stability, but the worst asynchrony stability. The second main finding revealed that for all patterns, audio-visual stimulation improved the stability of sensorimotor coordination but not of inter-manual coordination. The combination of visual and auditory modalities results in multisensory integration, which improves sensorimotor coordination but not inter-manual coordination. Both results suggest that there is dissociation between processes underlying sensorimotor synchronization (anticipation or reactivity) and processes underlying inter-manual coordination (motor control). This finding opens new perspectives to evaluate separately the possible sensorimotor and inter-manual coordination deficits present in movement disorders.

Modeling effects of cerebellar and basal ganglia lesions on adaptation and anticipation during sensorimotor synchronization.

This study addressed the role of subcortical brain structures in temporal adaptation and anticipation during sensorimotor synchronization. The performance of patients with cerebellar or basal ganglia lesions was compared with that of healthy control participants on tasks requiring the synchronization of drum strokes with adaptive and tempo-changing auditory pacing sequences. The precision of sensorimotor synchronization was generally lower in patients relative to controls (i.e., variability of asynchronies was higher in patients), although synchronization accuracy (mean asynchrony) was commensurate. A computational model of adaptation and anticipation (ADAM) was used to examine potential sources of individual differences in precision by estimating participants' use of error correction, temporal prediction, and the amount of variability associated with central timekeeping and peripheral motor processes. Parameter estimates based on ADAM indicate that impaired precision was attributable to increased variability of timekeeper and motor processes as well as to reduced temporal prediction in both patient groups. Adaptive processes related to continuously applied error correction were, by contrast, intact in patients. These findings highlight the importance of investigating how subcortical structures, including the cerebellum and basal ganglia, interact with a broader network of cortical regions to support temporal adaptation and anticipation during sensorimotor synchronization.

You are in sync with me: Neural correlates of interpersonal synchrony with a partner

Interpersonal synchrony is characterized by a temporary alignment of periodic behaviors with another person. This process requires that at least one of the two individuals monitors and adjusts his/her movements to maintain alignment with the other individual (the referent). Interestingly, recent research on interpersonal synchrony has found that people who are motivated to befriend an unfamiliar social referent tend to automatically synchronize with their social referents, raising the possibility that synchrony may be employed as an affiliation tool. It is unknown, however, whether the opposite is true; that is, whether the person serving as the referent of interpersonal synchrony perceives synchrony with his/her partner or experiences affiliative feelings toward the partner.To address this question, we performed a series of studies on interpersonal synchrony with a total of 100 participants. In all studies, participants served as the referent with no requirement to monitor or align their behavior with their partners. Unbeknown to the participants, the timings of their “partner’s” movements were actually determined by a computer program based on the participant’s (i.e., referent’s) behavior.Overall, our behavioral results showed that the referent of a synchrony task expressed greater perceived synchrony and greater social affiliation toward a synchronous partner (i.e., one displaying low mean asynchrony and/or a narrow asynchrony range) than with an asynchronous partner (i.e., one displaying high mean asynchrony and/or high asynchrony range). Our neuroimaging study extended these results by demonstrating involvement of brain areas implicated in social cognition, embodied cognition, self-other expansion, and action observation as correlates of interpersonal synchrony (vs. asynchrony). These findings have practical implications for social interaction and theoretical implications for understanding interpersonal synchrony and social coordination.

140. Effects of transcranial alternating current stimulation (tACS) on spontaneous motor tempo and sensorimotor synchronization: Preliminary data

We used transcranial alternating current stimulation (tACS) to modulate brain oscillations during spontaneous motor tempo and sensorimotor synchronization tasks to evaluate the effect of specific frequencies on motor performance. Six healthy subjects performed self-paced finger movements and auditory-paced finger tapping (synchronization–continuation task) with isochronous rhythmic sequences of 500 and 1500 ms interstimulus intervals (ISI). During each task, tACS was delivered to the left M1 (“reference” electrode on Pz) at an intensity of 1 mA in 5 randomized conditions: 5, 10, 20, 40 Hz, and sham. Baseline recordings (without tACS) were performed before and after each experimental session. In synchronization task with sequences of ISI 500 ms, 20 Hz tACS modified anticipatory mechanisms as revealed by a reduction of the negative mean asynchrony between the onset of the auditory cue and the motor response. However, this effect did not reach statistical significance due to the small sample. No effect emergent in the other conditions. We hypothesize that the reduction of the negative mean asynchrony may reflect a slowing of the motor output. These preliminary data are in line with previous studies in literature reporting specific effects of tACS at beta frequency on motor functions and cortical excitability.