Spontaneous social coordination has been extensively described in natural settings but so far no controlled methodological approaches have been employed that systematically advance investigations into the possible self-organized nature of bond formation and dissolution between humans. We hypothesized that, under certain contexts, spontaneous synchrony -a well-described phenomenon in biological and physical settings-could emerge spontaneously between humans as a result of information exchange. Here, a new way to quantify interpersonal interactions in real time is proposed. In a simple experimental paradigm, pairs of participants facing each other were required to actively produce actions, while provided (or not) with the vision of similar actions being performed by someone else. New indices of interpersonal coordination, inspired by the theoretical framework of coordination dynamics (based on relative phase and frequency overlap between movements of individuals forming a pair) were developed and used. Results revealed that spontaneous phase synchrony (i.e., unintentional in-phase coordinated behavior) between two people emerges as soon as they exchange visual information, even if they are not explicitly instructed to coordinate with each other. Using the same tools, we also quantified the degree to which the behavior of each individual remained influenced by the social encounter even after information exchange had been removed, apparently a kind of social memory.

The continuation paradigm is often used to investigate the behavioral and neural mechanisms of timing. Typically, a movement rate is established by pacing with a metronome. Then, the metronome is turned off and the subject continues at the established rate. Performance during continuation is assumed to be based on internal timing mechanisms. Here, we investigated the degree to which the neural activity underlying time representation depends on the initial pacing context, that is, whether pacing was established by moving in-phase (the usual procedure) or anti-phase (syncopation) with an auditory metronome. Functional MRI was measured from 14 subjects during four conditions: synchronized pacing, synchronized continuation, syncopated pacing, and syncopated continuation. In general, movements were timed consistently for all four conditions. However, a much broader network of activation was engaged during syncopation compared with synchronization, including increased activation in supplementary motor area, left premotor area, right thalamus, bilateral inferior frontal gyrus, and cerebellum. No differences were found when comparing continuation with the preceding pacing phase except for decreased activity in auditory-related regions due to the absence of the metronome. These results demonstrate that the cortical and subcortical areas recruited to support a simple motor timing task depend crucially on the method used to establish the temporal reference. Thus, the neural mechanisms underlying time and timing are highly flexible, reflecting the context in which the timing is established.T he ability of humans to accurately maintain temporal information after the removal of external environmental cues is often exploited to investigate the neural basis of internal timing mechanisms (1). An illustrative approach first used by Stevens (2) and popularized by Wing and Kristofferson (3) is the continuation paradigm. The task consists of two stages. In the first stage (termed pacing), movements are made to coincide with an external periodic stimulus or metronome. In the second so-called continuation stage, the metronome is removed and the subject is required to maintain movement at the rate previously established during pacing. During continuation it is assumed that timing is based on internal mechanisms that use a representation of the required interval developed during pacing. When applied to patient populations, this approach has been central in identifying cerebellum and basal ganglia as putative structures mediating these temporal processes during continuation (4-6). More recent functional imaging studies employing this paradigm have identified broader networks of cortical and subcortical structures underlying timing (7,8). Although these latter studies demonstrate that pacing and continuation, in addition to imposing similar task demands, activate substantially overlapping networks, the degree to which the neural areas supporting continuation are influenced by the network of neural activity generated during pacing has not ...

Apart from its natural relevance to cognition, music provides a window into the intimate relationships between production, perception, experience, and emotion. Here, emotional responses and neural activity were observed as they evolved together with stimulus parameters over several minutes. Participants listened to a skilled music performance that included the natural fluctuations in timing and sound intensity that musicians use to evoke emotional responses. A mechanical performance of the same piece served as a control. Before and after fMRI scanning, participants reported real-time emotional responses on a 2-dimensional rating scale (arousal and valence) as they listened to each performance. During fMRI scanning, participants listened without reporting emotional responses. Limbic and paralimbic brain areas responded to the expressive dynamics of human music performance, and both emotion and reward related activations during music listening were dependent upon musical training. Moreover, dynamic changes in timing predicted ratings of emotional arousal, as well as real-time changes in neural activity. BOLD signal changes correlated with expressive timing fluctuations in cortical and subcortical motor areas consistent with pulse perception, and in a network consistent with the human mirror neuron system. These findings show that expressive music performance evokes emotion and reward related neural activations, and that music's affective impact on the brains of listeners is altered by musical training. Our observations are consistent with the idea that music performance evokes an emotional response through a form of empathy that is based, at least in part, on the perception of movement and on violations of pulse-based temporal expectancies.

No abstract

Dynamic systems have proven to be well suited to describe a broad spectrum of human coordination behavior such synchronization with auditory stimuli. Simultaneous measurements of the spatiotemporal dynamics of electroencephalographic (EEG) and magnetoencephalographic (MEG) data reveals that the dynamics of the brain signals is highly ordered and also accessible by dynamic systems theory. However, models of EEG and MEG dynamics have typically been formulated only in terms of phenomenological modeling such as fixed-current dipoles or spatial EEG and MEG patterns. In this paper, it is our goal to connect three levels of organization, that is the level of coordination behavior, the level of patterns observed in the EEG and MEG and the level of neuronal network dynamics. To do so, we develop a methodological framework, which defines the spatiotemporal dynamics of neural ensembles, the neural field, on a sphere in three dimensions. Using magnetic resonance imaging we map the neural field dynamics from the sphere onto the folded cortical surface of a hemisphere. The neural field represents the current flow perpendicular to the cortex and, thus, allows for the calculation of the electric potentials on the surface of the skull and the magnetic fields outside the skull to be measured by EEG and MEG, respectively. For demonstration of the dynamics, we present the propagation of activation at a single cortical site resulting from a transient input. Finally, a mapping between finger movement profile and EEG/MEG patterns is obtained using Volterra integrals.