Synchronization in repetitive smooth movement requires perceptible events

Accurate timing performance during auditory–motor synchronization has been well documented for finger tapping tasks. It is believed that information pertaining to an event in movement production aids in detecting and correcting for errors between movement cycle completion and the metronome tone. Tasks with minimal event-related information exhibit more variable synchronization and less rapid error correction. Recent work from our laboratory has indicated that a task purportedly lacking an event structure (circle drawing) did not exhibit accurate synchronization or error correction (Studenka & Zelaznik, in press). In the present paper we report on two experiments examining synchronization in tapping and circle drawing tasks. In Experiment 1, error correction processes of an event-timed tapping timing task and an emergently timed circle drawing timing task were examined. Rapid and complete error correction was seen for the tapping, but not for the circle drawing task. In Experiment 2, a perceptual event was added to delineate a cycle in circle drawing, and the perceptual event of table contact was removed from the tapping task. The inclusion of an event produced a marked improvement in synchronization error correction for circle drawing, and the removal of tactile feedback (taking away an event) slightly reduced the error correction response of tapping. Furthermore, the task kinematics of circle drawing remained smooth providing evidence that event structure can be kinematic or perceptual in nature. Thus, synchronization and error correction, characteristic of event timing (Ivry, Spencer, Zelaznik, & Diedrichsen, 2002; Repp, 2005), depends upon the presence of a distinguishable source of sensory information at the timing goal.     

The influence of speed and force on bimanual finger tapping patterns.

The current study investigated factors that affect the stability of anti-phase bimanual finger tapping. Past research employing the order parameter and control parameter concepts, has identified frequency of movement as a control parameter that affects the stability of finger movement patterns (the order parameter). The present study investigated the hypothesis that multiple movement related variables can interact to influence the stability of an order parameter. Specifically, the combined effect of the rate of movement and movement force on the stability of bimanual finger tapping was examined. Participants were required to initiate an anti-phase tapping pattern under three different movement rate conditions (600, 400, and 200 ms), and were required to increase the force of one finger at the onset of a randomly presented stimulus. The results indicate that an increase in the force parameter at lower tapping rates (600 ms) did not affect the phase relation of the fingers, however at higher rates (200 and 400 ms), the introduction of a force parameter resulted in fluctuations of the phase relation of the fingers, which were followed by pattern shifts from anti-phase to in-phase tapping. The results indicate that movement force and rate of movement interact to influence the outcome of the tapping pattern. Further research is required to investigate force as a control parameter.     

Effects of feedback from active and passive body parts on spatial and temporal parameters in sensorimotor synchronization

Previous research on sensorimotor synchronization has manipulated the somatosensory information received from the tapping finger to investigate how feedback from an active effector affects temporal coordination. The current study explored the role of feedback from passive body parts in the regulation of spatiotemporal motor control parameters by employing a task that required finger tapping on one’s own skin at anatomical locations of varying tactile sensitivity. A motion capture system recorded participants’ movements as they synchronized with an auditory pacing signal by tapping with the right index finger on either their left index fingertip (Finger/Finger) or forearm (Finger/Forearm). Results indicated that tap timing was more variable, and movement amplitude was larger and more variable, when tapping on the finger than when tapping on the less sensitive forearm. Finger/Finger tapping may be impaired relative to Finger/Forearm tapping due to ambiguity arising through overlap in neural activity associated with tactile feedback from the active and the passive limb in the former. To compensate, the control system may strengthen the assignment of tap-related feedback to the active finger by generating correlated noise in movement kinematics and tap dynamics.     

Laterality differences for speed but not for control in sequential finger tapping

Multiple or sequential finger tapping is preferential to the dominant right hand with respect to speed. However, in more complex movement, variables other than speed become important. The present investigation uses a sequential finger-tapping task which permits assessment of between-hands differences with respect to rate and control of movement, with and without vision. 36 right-handed normal adults rapidly tapped their fingers in sequential order on a block (2.54 cm. sq.), trying not to move the block. Analyses of variance (mode x hand) performed for taps and shift of the block show the right hand to be faster than the left hand with and without vision, adding further to the notion that the left hemisphere predominates in increases in rapid movement and in sequencing aspects of motor activity. However, while both hands were steadier with vision than without, there were no between-hand differences with regard to control, suggesting equivalency of cerebral function for factors of manual sequencing other than speed.     

Motor variability in elicited repeated bout rate enhancement is associated with higher sample entropy

In this study we investigated motor variability in individuals who showed (responders) and who did not show (non-responders) a behavioural phenomenon termed repeated bout rate enhancement. The phenomenon is characterized by an increase of the freely chosen index finger tapping rate during the second of two consecutive tapping bouts. It was hypothesized that responders would perform (i) tapping with a lower magnitude, but more complex structure of variability than non-responders and (ii) bout 2 with a lower magnitude and increased complexity of variability than bout 1, as opposed to non-responders. Individuals (n = 102) performed two 3-min tapping bouts separated by 10 min rest. Kinetic and kinematic recordings were performed. Standard deviation (SD), coefficient of variation (CV), and sample entropy (SaEn), representing magnitude and complexity of variability, were computed. For responders, SaEn of vertical displacement of the index finger was higher than for non-responders (p = .046). Further, SaEn of vertical force and vertical displacement was higher in bout 2 than in bout 1 for responders (p < .001 and p = .006, respectively). In general, SD of vertical displacement was lower in bout 2 than in bout 1 (p < .001). SaEn of vertical force was higher in bout 2 than in bout 1 (p = .009). The present lower SD and higher SaEn values of vertical force and displacement time series in bout 2 as compared to bout 1 suggest differences in the dynamics of finger tapping. Further, it is possible that the increases in SaEn of vertical displacement reflected a greater adaptability in the dynamics of motor control among responders compared with non-responders.     

Timing of movement phases of a repeated response

How can one determine the nature of timing control that exists among various distinct phases of movement in a repetitive activity? A statistical approach is suggested and is exemplified by reference to data on the timing of two phases of movement, arrival at and departure from the response plate, in repetitive finger tapping. Two contrasting models are presented, and the predictions for the covariation of the various intervals between the two movement phases are compared. Data on finger tapping support the model that assumes the initiation of each phase is centrally determined without reference to the time of occurrence of the immediately preceding phase.     

Phase Correction Following a Perturbation in Sensorimotor Synchronization Depends on Sensory Information

In models of sensorimotor synchronization, it is generally assumed that phase correction occurs in response to information about sensorimotor asynchrony or relative phase. Without such feedback, a phase perturbation in the motor activity should not be followed by phase correction. Alternatively, internally generated temporal expectations could provide a basis for phase correction in the absence of feedback. To test those hypotheses, the author conducted an experiment in which participants (N = 8) tapped their finger in synchrony with isochronous auditory sequences containing a single shifted event onset, after which there could be a gap of up to 3 missing events. Participants were instructed to not react to the shifted event and to continue tapping regularly during any gap. The shifted event caused an involuntary phase shift of the following tap. The shift was corrected if the sequence continued, but during a gap, the shift persisted without correction. Those results confirm that sensory feedback is necessary for phase correction to occur.     

Rate and variability of finger tapping as measures of lateralized concurrent task effects

Using a sample of 48 normal right-handed adults, we assessed the effects of oral reading on concurrent unimanual finger tapping under all combinations of instructional set (speeded vs. consistent tapping), tapping movement (repetitive vs. alternating), task emphasis (reading emphasized vs. tapping emphasized), and tapping hand. Change in tapping rate and variability was measured relative to the corresponding single task control condition. Reading decreased the rate of speeded finger tapping but increased the rate of consistent tapping. In both instances, the right hand was affected more than the left hand. Asymmetries were comparable for repetitive and alternating tapping. When measured in terms of variability, however, effects were largely symmetric. The findings clarify the conditions under which lateralized concurrent task effects are most likely to occur and show that such effects are not statistical artifacts. It appears that subjects attempt to coordinate the timing of concurrent activities and that speech timing is more strongly linked to right-hand control than to left-hand control in right-handers.     

Effects of speaking upon the rate and variability of concurrent finger tapping in children

Tapping rate and variability were measured as 73 normal, right-handed children in Grades 1–4 engaged in speeded unimanual finger tapping with and without concurrent recitation. Speaking reduced the rate of tapping and increased its variability to a greater extent in younger children than in older children. Developmental changes in variability but not rate were attributable to a greater number of lengthy (>500 ms) pauses in the tapping of younger children. Speaking slowed the right hand more than the left, and the degree of this asymmetry was constant across grade levels. The right-hand effect for tapping rate was not attributable to lengthy pauses. In contrast, asymmetric increases in tapping variability occurred only among children in Grade 1 and only when lengthy pauses were included in the data. The results implicate three mechanisms of intertask interference: one involving capacity limitations, a second involving cross-talk between motor control mechanisms for speech and finger movement, respectively, and a third factor involving occasional diversion of attention from tapping to speaking. These mechanisms are discussed in relation to developmental changes in mental capacity.     

Automaticity and voluntary control of phase correction following event onset shifts in sensorimotor synchronization

Seven experiments show that an event onset shift (EOS) in an auditory sequence causes an involuntary phase correction response (PCR) in synchronized finger tapping. This PCR is (a) equally large in inphase and antiphase tapping; (b) reduced but still present when the EOS occurs in either of two interleaved (target-distractor) sequences; (c) unaffected by increased pitch separation between these sequences; (d) asymptotic in magnitude as EOS magnitude increases, unlike the intentional PCR to expected phase shifts; and (e) enhanced when the EOS precedes the onset of tapping, because of phase resetting. Thus, phase correction is revealed to be partially automatic and partially under voluntary control, and to be based mainly on temporal information derived from simple onset detection.     

The role of emotional context in facilitating imitative actions

In two experiments, we explored whether emotional context influences imitative action tendencies. To this end, we examined how emotional pictures, presented as primes, affect imitative tendencies using a compatibility paradigm. In Experiment 1, when seen index finger movements (lifting or tapping) and pre-instructed finger movements (tapping) were the same (tapping–tapping, compatible trials), participants were faster than when they were different (lifting–tapping, incompatible trials). This compatibility effect was enhanced when the seen finger movement was preceded by negative primes compared with positive or neutral primes. In Experiment 2, using only negative and neutral primes, the influence of negative primes on the compatibility effect was replicated with participants performing two types of pre-instructed finger movements (tapping and lifting). This emotional modulation of the compatibility effect was independent of the participants' trait anxiety level. Moreover, the emotional modulation pertained primarily to the compatible conditions, suggesting facilitated imitation due to negatively valent primes rather than increased interference. We speculate that negative stimuli increase imitative tendencies as a natural response in potential flight-or-fight situations.     

Perfect Phase Correction in Synchronization With Slow Auditory Sequences

Phase correction during synchronization (finger tapping) with an isochronous auditory sequence is typically imperfect, requiring several taps to complete. However, two independent hypotheses predict that phase correction should approach perfection when the sequence tempo is slow. The present results confirm this prediction. The experiment used a phase perturbation method and a group of musically trained participants. As the sequence interonset interval increased from 300 to 1200 ms, the phase correction response to perturbations increased and approached instantaneous phase resetting between 700 and 1200 ms, depending on the individual. A possible explanation of this finding is that emergent timing of the periodic finger movement vanishes as the movement frequency decreases and thus ceases to compete with event-based timing.     

Perfect phase correction in synchronization with slow auditory sequences

Phase correction during synchronization (finger tapping) with an isochronous auditory sequence is typically imperfect, requiring several taps to complete. However, two independent hypotheses predict that phase correction should approach perfection when the sequence tempo is slow. The present results confirm this prediction. The experiment used a phase perturbation method and a group of musically trained participants. As the sequence interonset interval increased from 300 to 1200 ms, the phase correction response to perturbations increased and approached instantaneous phase resetting between 700 and 1200 ms, depending on the individual. A possible explanation of this finding is that emergent timing of the periodic finger movement vanishes as the movement frequency decreases and thus ceases to compete with event-based timing.     

Phase correction, phase resetting, and phase shifts after subliminal timing perturbations in sensorimotor synchronization.

Recent studies of synchronized finger tapping have shown that perceptually subliminal phase shifts in an auditory sequence are rapidly compensated for in the motor activity (B. H. Repp, 2000a). Experiment 1 used a continuation-tapping task to confirm that this compensation is indeed a phase correction, not an adjustment of the central timekeeper period. Experiments 2-5 revealed that this phase correction occurs even when there is no ordinary sensorimotor asynchrony--when the finger taps are in antiphase or arbitrary phase relative to the auditory sequence (Experiments 2 and 3) or when the tap coinciding with the sequence phase shift is withheld (Experiments 4 and 5). The phase correction observed in the latter conditions was instantaneous, which suggests that phase resetting occurs when the motor activity is discontinuous. A prolonged phase shift suggestive of overcompensation was observed in some conditions, which poses a challenge to pure phase correction models.     

Latency and duration of the action interruption in surprise

Cognitive and biological theories of emotion consider surprise as an emotional response to unexpected events. Four experiments examined the latency and the duration of one behavioural component of surprise: The interruption of ongoing action. Participants were presented with an unannounced visual event—the appearance of new perceptual objects—during the execution of a continuous action—a rapid alternate finger tapping—which allowed a precise measurement of the latency, and the duration of an action interruption induced by the surprising event. Of the participants, 78% interrupted the tapping with a mean latency of 214 ms and a mean duration of 995 ms. Variations of the number and perceptual heterogeneity of the new objects revealed that the perceptual analysis of the surprising event contributes significantly to the interruption duration.     

Response timing variability: coherence of kinematic and EMG parameters

A detailed kinematic and electromyographic (EMG) analysis of single degree of freedom timing responses is reported to (a) determine the coherence of kinematic and EMG variability to the reduced timing error variability exhibited with amplitude increments within a given criterion movement time and (b) understand the temporal organization of various movement parameters in simple responses. The data reveal that the variability of kinematic (time to peak acceleration, duration of acceleration phase, time to peak deceleration) and EMG (duration of agonist burst, duration of antagonist burst, time to antagonist burst) timing parameters decreased with increments of average velocity in a manner consistent with the variable timing error. In addition, the coefficient of variation for peak acceleration, peak deceleration, and integrated EMG of the agonist burst followed the same trend. Increasing average movement velocity also led to decreases in premotor and motor reaction times. Overall, the findings suggest a strong coherence between the variability of response outcome, kinematic, and EMG parameters.     

Response Timing Variability

A detailed kinematic and electromyographic (EMG) analysis of single degree of freedom timing responses is reported to (a) determine the coherence of kinematic and EMG variability to the reduced timing error variability exhibited with amplitude increments within a given criterion movement time and (b) understand the temporal organization of various movement parameters in simple responses. The data reveal that the variability of kinematic (time to peak acceleration, duration of acceleration phase, time to peak deceleration) and EMG (duration of agonist burst, duration of antagonist burst, time to antagonist burst) timing parameters decreased with increments of average velocity in a manner consistent with the variable timing error. In addition, the coefficient of variation for peak acceleration, peak deceleration, and integrated EMG of the agonist burst followed the same trend. Increasing average movement velocity also led to decreases in premotor and motor reaction times. Overall, the findings suggest a strong coherence between the variability of response outcome, kinematic, and EMG parameters.     

Coordination of a Discrete Response With Periodic Finger Tapping: Additional Experimental Aspects for a Subtle Mechanism

The authors investigated the coordination of periodic right-hand tapping with single stimulus-evoked discrete lefthand taps to check for task interactions and a possible relationship between phase resetting (see tapping literature; e.g., J. Yamanishi, M. Kawato, & R. Suzuki, 1979) and phase entrainment (see tremor literature; e.g., R. J. Elble, C. Higgins, & L. Hughes, 1994). The experimental paradigm employs a dual-task condition as used by K. Yoshino, K. Takagi, T. Nomura, S. Sato, and M. Tonoike (2002), and it includes normal tapping and isometric tapping with the authors recording finger positions and ground contact forces. Four different types of coordination schemes were observed in tapping behavior: marginal tapping interaction (MTI), periodic tap retardation (PTR), periodic tap hastening (PTH), and discrete tap entrainment (DTE); MTI and PTR correspond to the phase-resetting effect for the coordination of periodic tapping with single discrete taps. The novel aspect of the study described in this article includes the impact of the periodic tapping on the discrete tap timing and the hastening of the periodic tapping due to the discrete tap behaviors resulting in a synchronized execution of the two concurrent tapping tasks. All participants showed a dominant tapping behavior, but they all used the other nondominant forms of the four reported coordination schemes in some trials too, which reflects possible constraints of the sensorimotor system in handling two competing tasks.     

Processes underlying adaptation to tempo changes in sensorimotor synchronization

In synchronizing finger taps with an auditory sequence, a small sudden tempo ("step") change in the sequence tends to be followed by rapid adaptation of the tapping period but slow adaptation of the relative phase of the taps, whereas a larger step change leads to initial period overshoot followed by rapid adaptation of both period and phase [M.H. Thaut, R.A. Miller, L.M. Schauer, Biological Cybernetics 79 (1998a) 241-250]. Experiment 1 replicated these findings and showed that the transition between the two patterns of adaptation occurs near the perceptual detection threshold for a tempo change. A reasonable explanation of these data was provided by a dual-process model of internal error correction [J. Mates, Biological Cybernetics 70 (1994a) 463-473, 70 (1994b) 475-484], with the added assumption that one process (period correction) depends on conscious awareness of a tempo change whereas the other (phase correction) does not. This assumption received support in Experiment 2, where a synchronization-continuation tapping task was used in combination with perceptual judgments to probe into the process of period correction following step changes. The results led to the conclusion that rapid adaptation of the tapping period to a small, undetected tempo change is in fact due to rapid internal phase correction, whereas slow adaptation of the relative phase of the taps is due to slow internal period correction.     

Freely Chosen Index Finger Tapping Frequency Is Increased in Repeated Bouts of Tapping

Healthy individuals (n = 40) performed index finger tapping at freely chosen frequency during repeated bouts and before and after near-maximal muscle action consisting of 3 intense flexions of the index finger metacarpal phalangeal joint. One experiment showed, unexpectedly, that a bout of tapping increased the tapping frequency in the subsequent bout. Thus, a cumulating increase of 8.2 ± 5.4% (p < .001) occurred across 4 bouts, which were all separated by 10 min rest periods. Follow-up experiments revealed that tapping frequency was still increased in consecutive bouts when rest periods were extended to 20 min. Besides, near-maximal muscle activation, followed by 5 min rest, did not affect the tapping frequency. In conclusion, freely chosen tapping frequency was increased in repeated bouts of tapping, which were separated by 10–20 min rest periods. The observed phenomenon is suggested to be termed repeated bout rate enhancement.