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.

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MRI-guided focused ultrasound therapy for leiomyoma can result in nonperfused volume ratio and shrinkage that exceed those in previous clinical trials because the treatment guidelines have been relaxed to allow a greater amount of tissue ablation. The results suggest that a larger nonperfused volume ratio can be achieved, resulting in greater shrinkage and improved relief of symptoms.

Inherent differences in difficulty between on the beat (synchronization) and off the beat (syncopation) coordination modes are well known. Synchronization is typically quite easy and, once begun, may be carried out with little apparent attention demand. Syncopation tends to be difficult, even though it has been described as a simple, phase-shifted version of a synchronized pattern. We hypothesize that syncopation, unlike synchronization, is organized on a cycle-by-cycle basis, thereby imposing much greater preparatory and attentional demands on the central nervous system. To test this hypothesis we used fMRI to measure the BOLD response during syncopation and synchronization to an auditory stimulus. We found that the distribution of cortical and subcortical areas involved in intentionally coordinating movement with an external metronome depends on the timing pattern employed. Both synchronized and syncopated patterns require activation of contralateral sensorimotor and caudal supplementary motor cortices as well as the (primarily ipsilateral) cerebellum. Moving off the beat, however, requires not only additional activation of the cerebellum but also the recruitment of another network comprised of the basal ganglia, dorsolateral premotor, rostral supplementary motor, prefrontal, and temporal association cortices. No areas were found to be more active during synchronization than syncopation. The functional role of the cortical and subcortical regions areas involved in syncopation supports the hypothesis that whereas synchronization requires little preparation and monitoring, syncopated movements are planned and executed individually on each perception-action cycle.

The aim of this study was to explore the role of attention in pulse and meter perception using complex rhythms. We used a selective attention paradigm in which participants attended to either a complex auditory rhythm or a visually presented word list. Performance on a reproduction task was used to gauge whether participants were attending to the appropriate stimulus. We hypothesized that attention to complex rhythms – which contain no energy at the pulse frequency – would lead to activations in motor areas involved in pulse perception. Moreover, because multiple repetitions of a complex rhythm are needed to perceive a pulse, activations in pulse-related areas would be seen only after sufficient time had elapsed for pulse perception to develop. Selective attention was also expected to modulate activity in sensory areas specific to the modality. We found that selective attention to rhythms led to increased BOLD responses in basal ganglia, and basal ganglia activity was observed only after the rhythms had cycled enough times for a stable pulse percept to develop. These observations suggest that attention is needed to recruit motor activations associated with the perception of pulse in complex rhythms. Moreover, attention to the auditory stimulus enhanced activity in an attentional sensory network including primary auditory cortex, insula, anterior cingulate, and prefrontal cortex, and suppressed activity in sensory areas associated with attending to the visual stimulus.

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