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This study examined the relation between movement amplitude and tempo during self-paced rhythmic finger tapping to test a preferred velocity account of the preferred tempo construct. Preferred tempo refers to the concept that individuals have preferences for the pace of actions or events in their environment (e.g., the desired pace of walking or tempo of music). The preferred velocity hypothesis proposes that assessments of preferred tempo do not represent a pure time preference independent of spatial movement characteristics, but rather reflects a preference for an average movement velocity, predicting that preferred tempo will depend on movement amplitude. We tested this by having participants first perform a novel spontaneous motor amplitude (SMA) task in which they repetitively tapped their finger at their preferred amplitude without instructions about tapping tempo. Next, participants completed the spontaneous motor tempo (SMT) task in which they tapped their finger at their preferred tempo without instructions about tapping amplitude. Finally, participants completed a target amplitude version of the SMT task where they tapped at their preferred tempo at three target amplitudes (low, medium, and high). Participants (1) produced similar amplitudes and tempi regardless of instructions to produce either their preferred amplitude or preferred tempo, maintaining the same average movement velocity across SMA and SMT tasks and (2) altered their preferred tempo for different target amplitudes in the direction predicted by their estimated preferred velocity from the SMA and SMT tasks. Overall, results show the interdependence of movement amplitude and tempo in tapping assessments of preferred tempo. [ABSTRACT FROM AUTHOR]

Obesity has been associated with poorer sensorimotor performance. However, it remains unclear whether these obesity-related impairments can be mitigated by practice. In the present study, we sought to investigate the effects of practice on performing and learning a temporal estimation task, in women with and without obesity. The experimental task consisted of synchronizing the arrival of two rectangles at a target point. Limited to the pressing of a switch, the task was intended to minimize possible muscular fatigue, self-generated perturbations to balance and the need to accelerate/decelerate body segments. Participants were allowed to choose the displacement velocity of the rectangle they controlled and were informed that they would not be offered any choice over it during a test to come. To control for the effect of different body positions on sensorimotor performance and learning, the 19 women with obesity (BMI = 40.0 + 7.33, age = 44.2 + 6.6) and 20 without obesity (BMI = 22.3 + 1.95, age = 43 + 6.9) were assigned into 4 groups, according to their BMI and body position assumed during practice (standing upright with feet together or sitting). As no significant differences concerning body position were found, the data were reanalysed disregarding this factor. Results revealed that while both groups reduced errors during the Acquisition, participants with obesity showed poorer performance (Acquisition) and sensorimotor learning (Transfer). Given the experimental task and adopted procedures, our results tend to support the hypothesis that hindered perception and/or integration of sensory information is associated with obesity. [ABSTRACT FROM AUTHOR]

Visual motion stimuli can sometimes distort our perception of time. This effect is dependent on the apparent speed of the moving stimulus, where faster stimuli are usually perceived lasting longer than slower stimuli. Although it has been shown that neural and cognitive processing of biological motion stimuli differ from non-biological motion stimuli, no study has yet investigated whether perceived durations of biological stimuli differ from non-biological stimuli across different speeds. Here, a prospective temporal reproduction task was used to assess that question. Biological motion stimuli consisted of a human silhouette running in place. Non-biological motion stimuli consisted of a rectangle moving in a pendular way. Amount and plausibility of movement for each stimulus and frame-rate (speed) were evaluated by an independent group of participants. Although the amount of movement perceived was positively correlated to frame rate both for biological and non-biological stimuli, movie clips involving biological motion stimuli were judged to last longer than non-biological motion stimuli only at frame rates for which movement was rated as plausible. These results suggest that plausible representations of biomechanical movement induce additional temporal distortions to those modulated by increases in stimulus speed. Moreover, most studies reporting neural and cognitive differences in the processing of biological and non-biological motion stimuli acquired neurophysiological data using fMRI. Here, we report differences in the processing of biological and non-biological motion stimuli across different speeds using functional near-infrared spectroscopy (fNIRS), a less costly and portable form of neurophysiological data acquisition. [ABSTRACT FROM AUTHOR]

In a previous study, we found that haptic guidance from a robotic steering wheel can improve short-term learning of steering of a simulated vehicle, in contrast to several studies of other tasks that had found that the guidance either impairs or does not aid motor learning. In this study, we examined whether haptic guidance-as-needed can improve long-term retention (across 1 week) of the steering task, with age and initial skill level as independent variables. Training with guidance-as-needed allowed all participants to learn to steer without experiencing large errors. For young participants (age 18–30), training with guidance-as-needed produced better long-term retention of driving skill than did training without guidance. For older participants (age 65–92), training with guidance-as-needed improved long-term retention in tracking error, but not significantly. However, for a subset of less skilled, older subjects, training with guidance-as-needed significantly improved long-term retention. The benefits of guidance-based training were most evident as an improved ability to straighten the vehicle direction when coming out of turns. In general, older participants not only systematically performed worse at the task than younger subjects (errors ∼3 times greater), but also apparently learned more slowly, forgetting a greater percentage of the learned task during the 1 week layoffs between the experimental sessions. This study demonstrates that training with haptic guidance can benefit long-term retention of a driving skill for young and for some old drivers. Training with haptic guidance is more useful for people with less initial skill.

Performance errors drive motor learning for many tasks. Some researchers have suggested that reducing performance errors with haptic guidance can benefit learning by demonstrating correct movements, while others have suggested that artificially increasing errors will force faster and more complete learning. This study compared the effect of these two techniques--haptic guidance and error amplification--as healthy subjects learned to play a computerized pinball-like game. The game required learning to press a button using wrist movement at the correct time to make a flipper hit a falling ball to a randomly positioned target. Errors were decreased or increased using a robotic device that retarded or accelerated wrist movement, based on sensed movement initiation timing errors. After training with either error amplification or haptic guidance, subjects significantly reduced their timing errors and generalized learning to untrained targets. However, for a subset of more skilled subjects, training with amplified errors produced significantly greater learning than training with the reduced errors associated with haptic guidance, while for a subset of less skilled subjects, training with haptic guidance seemed to benefit learning more. These results suggest that both techniques help enhanced performance of a timing task, but learning is optimized if training subjects with the appropriate technique based on their baseline skill level.

Grip force has been studied widely in a variety of interaction and movement tasks, however, not much is known about the timing of the grip force control in preparation for interaction with objects. For example, it is unknown whether and how the temporal preparation for a collision is related to (the prediction of) the impact load. To study this question, we examined the anticipative timing of the grip force in preparation for impact loads. We designed a collision task with different types of load forces in a controlled virtual environment. Participants interacted with a robotic device (KINARM, BKIN Technologies, Kingston) whose handles were equipped with force sensors which the participants held in precision grip. Representations of the hand and objects were visually projected on a virtual reality display and forces were applied onto the participant's hand to simulate a collision with the virtual objects. The collisions were alternating between the two hands to allow transfer and learning between the hands. The results show that there is immediate transfer of object information between the two hands, since the grip force levels are (almost) fully adjusted after one collision with the opposite hand. The results also show that the grip force levels are nicely adjusted based on the mass and stiffness of the object. Surprisingly, the temporal onset of the grip force build up did not depend on the impact load, so that participants avoid slippage by adjusting the other grip force characteristics (e.g., grip force level and rate of change), therefore considering these self-imposed timing constraints. With the use of catch trials, for which no impact occurred, we further analyzed the temporal profile of the grip force. The catch trial data showed that the timing of the grip force peak is also independent of the impact load and its timing, which suggests a time-locked planning of the complete grip force profile. [ABSTRACT FROM AUTHOR]

Both movement and neural activity in humans can be entrained by the regularities of an external stimulus, such as the beat of musical rhythms. Neural entrainment to auditory rhythms supports temporal perception, and is enhanced by selective attention and by hierarchical temporal structure imposed on rhythms. However, it is not known how neural entrainment to rhythms is related to the subjective experience of groove (the desire to move along with music or rhythm), the perception of a regular beat, the perception of complexity, and the experience of pleasure. In two experiments, we used musical rhythms (from Steve Reich's Clapping Music) to investigate whether rhythms that are performed by humans (with naturally variable timing) and rhythms that are mechanical (with precise timing), elicit differences in (1) neural entrainment, as measured by inter-trial phase coherence, and (2) subjective ratings of the complexity, preference, groove, and beat strength of rhythms. We also combined results from the two experiments to investigate relationships between neural entrainment and subjective perception of musical rhythms. We found that mechanical rhythms elicited a greater degree of neural entrainment than performed rhythms, likely due to the greater temporal precision in the stimulus, and the two types only elicited different ratings for some individual rhythms. Neural entrainment to performed rhythms, but not to mechanical ones, correlated with subjective desire to move and subjective complexity. These data, therefore, suggest multiple interacting influences on neural entrainment to rhythms, from low-level stimulus properties to high-level cognition and perception. [ABSTRACT FROM AUTHOR]

Field dependence-independence (FDI) is a stable dimension of individual functioning, transversal to different cognitive domains. While the role of some individual variables in time perception has received considerable attention, it is not clear whether and how FDI influences timing abilities. In this study, we tested the hypothesis that FDI differently affects timing performance depending on whether the task requires cognitive restructuring. Participants were assessed for FDI using the embedded figures test (EFT). They performed a prospective timing task, reproducing the duration of a flickering stimulus, and a retrospective timing task, estimating the duration of the task. We expected performance of field-dependent (FD) and field-independent (FI) individuals not to differ in the prospective task, since restructuring of task material is not needed to reproduce the stimulus duration. Conversely, we predicted that FI individuals should be more accurate than FD ones in the retrospective condition, involving restructuring skills. Results show that while both FD and FI individuals under-reproduced the stimulus duration in the prospective task, only FD participants significantly underestimated the duration of the timing task in the retrospective condition. These results suggest that differences across FD and FI individuals are apparent in timing only when the task requires high-level cognitive processing; conversely, these differences do not affect basic sensory processing. [ABSTRACT FROM AUTHOR]

To promote motor learning, robotic devices have been used to improve subjects’ performance by guiding desired movements (haptic guidance—HG) or by artificially increasing movement errors to foster a more rapid learning (error amplification—EA). To better understand the neurophysiological basis of motor learning, a few studies have evaluated brain regions activated during EA/HG, but none has compared both approaches. The goal of this study was to investigate using fMRI which brain networks were activated during a single training session of HG/EA in healthy adults learning to play a computerized pinball-like timing task. Subjects had to trigger a robotic device by flexing their wrist at the correct timing to activate a virtual flipper and hit a falling ball towards randomly positioned targets. During training with HG/EA, subjects’ timing errors were decreased/increased, respectively, by the robotic device to delay or accelerate their wrist movement. The results showed that at the beginning of the training period with HG/EA, an error-detection network, including cerebellum and angular gyrus, was activated, consistent with subjects recognizing discrepancies between their intended actions and the actual movement timing. At the end of the training period, an error-detection network was still present for EA, while a memory consolidation/automatization network (caudate head and parahippocampal gyrus) was activated for HG. The results indicate that training movement with various kinds of robotic input relies on different brain networks. Better understanding the neurophysiological underpinnings of brain processes during HG/EA could prove useful for optimizing rehabilitative movement training for people with different patterns of brain damage. [ABSTRACT FROM AUTHOR]

Previous work on sensorimotor synchronization has investigated the dynamics of finger tapping and how individual movement trajectories contribute to timing accuracy via asymmetry in movement velocities. The present study investigated sensorimotor synchronization (in-phase) and syncopation (anti-phase) to both an auditory metronome and a visual flashing light at multiple frequencies to understand how individual movement phases contribute to the variability of timekeeping and error correction in different sensory modalities and with different task constraints. Results demonstrate that the proportional time spent in both the upward phase of movement and the holding phase of movement (time spent on the surface of the table) remain relatively invariant across both stimulus modalities and across tapping styles (syncopation and synchronization), but changes with interval duration, increasing as interval duration increases. The time spent in the downward phase of movement did significantly differ across stimulus modality and tapping style, increasing during both visuomotor timing and syncopation, accompanied by a significant decrease in flexion velocity during syncopation. Extension velocity and flexion time were found to be the main contributors to differences between visual and auditory timing, while flexion velocity and flexion time were found to be the main contributors to differences between synchronization and syncopation. No correlations were found between asynchrony and the upward, downward, or holding phases of movement, suggesting the existence of multiple error correction strategies. [ABSTRACT FROM AUTHOR]

Humans display a natural tendency to move to the beat of music, more than to the rhythm of any other auditory stimulus. We typically move with music, but rarely with speech. This proclivity is apparent early during development and can be further developed over the years via joint dancing, singing, or instrument playing. Synchronization of movement to the beat can thus improve with age, but also with musical experience. In a previous study, we found that music perturbed synchronization with a metronome more than speech fragments; music superiority disappeared when distractors shared isochrony and the same meter (Dalla Bella et al., PLoS One 8(8):e71945, 2013). Here, we examined if the interfering effect of music and speech distractors in a synchronization task is influenced by musical training. Musicians and non-musicians synchronized by producing finger force pulses to the sounds of a metronome while music and speech distractors were presented at one of various phase relationships with respect to the target. Distractors were familiar musical excerpts and fragments of children poetry comparable in terms of beat/stress isochrony. Music perturbed synchronization with the metronome more than speech did in both groups. However, the difference in synchronization error between music and speech distractors was smaller for musicians than for non-musicians, especially when the peak force of movement is reached. These findings point to a link between musical training and timing of sensorimotor synchronization when reacting to music and speech distractors. [ABSTRACT FROM AUTHOR]

Sensorimotor timing deficits are considered central to attention-deficit/hyperactivity disorder (ADHD). However, the tasks establishing timing impairments often involve interconnected processes, including low-level sensorimotor timing and higher level executive processes such as attention. Thus, the source of timing deficits in ADHD remains unclear. Low-level sensorimotor timing can be isolated from higher level processes in a finger-tapping task that examines the motor response to unexpected shifts of metronome onsets. In this study, adults with ADHD and ADHD-like symptoms ( n = 25) and controls ( n = 26) performed two finger-tapping tasks. The first assessed tapping variability in a standard tapping task (metronome-paced and unpaced). In the other task, participants tapped along with a metronome that contained unexpected shifts (±15, 50 ms); the timing adjustment on the tap following the shift captures pre-attentive sensorimotor timing (i.e., phase correction) and thus should be free of potential higher order confounds (e.g., attention). In the standard tapping task, as expected, the ADHD group had higher timing variability in both paced and unpaced tappings. However, in the pre-attentive task, performance did not differ between the ADHD and control groups. Together, results suggest that low-level sensorimotor timing and phase correction are largely preserved in ADHD and that some timing impairments observed in ADHD may stem from higher level factors (such as sustained attention). [ABSTRACT FROM AUTHOR]

Cerebellar participation in timing and sensory-motor sequences has been supported by several experimental and clinical studies. A relevant role of the cerebellum in timing of conditioned responses in the range of milliseconds has been demonstrated, but less is known regarding the role of the cerebellum in supra-second timing of operant responses. A dissociated role of the cerebellum and striatum in timing in the millisecond and second range had been reported, respectively. The climbing fibre-Purkinje cell synapse is crucial in timing models; thus, the aberrant connection between these cellular elements is a suitable model for evaluating the contribution of the cerebellum in timing in the supra-second range. The aberrant connection between climbing fibres and Purkinje cells was induced by administration of the antagonist of NMDA receptors MK-801 to Sprague-Dawley rats at postnatal days 7-14. The timing of an operant response with two fixed intervals (5 and 8 s) and egocentric sequential learning was evaluated in 60-day-old adult rats. The aberrant connections caused a reduced accuracy in the timing of the instrumental response that was more evident in the 8-s interval and a reduced number of successive correct responses (responses emitted in the correct second without any other response between them) in the 8-s interval. In addition, an inability to incorporate new information in a sequence previously learned in egocentric-based sequence learning was apparent in rats with aberrant CF-PC synapses. These results support a relevant role for the cerebellum in the fine-tuning of the timing of operant responses in the supra-second range. [ABSTRACT FROM AUTHOR]

When performing a rapid manual interception, targets moving under constant motion are often intercepted with greater accuracy when compared to targets moving under accelerated motion. Usually, accelerated targets are timed too late and decelerating ones too early. The present experiment sought to investigate whether these differences in performance when intercepting targets moving under constant and accelerated motions change after a short period of practice. The task involved striking targets that moved along a straight track by moving forward a manipulandum that moved along a slide perpendicular to the target's motion. Participants were allocated to one of the three experimental groups, defined according to the type of motion of the moving targets: constant speed, constant acceleration, and constant deceleration. Results showed that after some practice participants were able to intercept (positive and negative) accelerating moving targets as accurately as constant speed targets. These results suggest that people might be able to learn how to intercept accelerating targets, corroborating the results of some recent studies. [ABSTRACT FROM AUTHOR]

The nature of the relationship between timing and cognition remains poorly understood. Cognitive control is known to be involved in discrete timing tasks involving durations above 1 s, but has not yet been demonstrated for repetitive motor timing below 1 s. We examined the latter in two continuation tapping experiments, by varying the cognitive load in a concurrent task. In Experiment 1, participants repeated a fixed three finger sequence (low executive load) or a pseudorandom sequence (high load) with either 524-, 733-, 1024- or 1431-ms inter-onset intervals (IOIs). High load increased timing variability for 524 and 733-ms IOIs but not for the longer IOIs. Experiment 2 attempted to replicate this finding for a concurrent memory task. Participants retained three letters (low working memory load) or seven letters (high load) while producing intervals (524- and 733-ms IOIs) with a drum stick. High load increased timing variability for both IOIs. Taken together, the experiments demonstrate that cognitive control processes influence sub-second repetitive motor timing. [ABSTRACT FROM AUTHOR]

The purpose of the current study was to examine the processes involved in the preparation of timing during response initiation and execution through the use of a startling acoustic stimulus (SAS). In Experiment 1, participants performed a delayed response task in which a two key-press movement was to be initiated 200 ms after an imperative signal (IS) with either a short (200 ms) or long (500 ms) interval between key-presses. On selected trials, a SAS was presented to probe the preparation processes associated with the initiation delay and execution of the inter-key interval. The SAS resulted in a significant decrease in the initiation time, which was attributed to a speeding of pacemaker pulses used to time the delay interval, caused by an increased activation due to the SAS. Conversely, the SAS delayed the short inter-key interval, which was attributed to temporary interference with cortical processing. In Experiment 2, participants performed a 500-ms delayed response task involving two key-presses 200 ms apart. In this condition, the SAS resulted in significantly decreased initiation time and a delayed inter-key interval ( p = .053). Collectively, these results support a different timeline for the preparation of the delay interval, which is thought to be prepared in advance of the IS, and the inter-key interval, which is thought to be prepared following the IS. This conclusion provides novel information with regard to timing preparation that is consistent with models in which response preparation, initiation, and execution are considered separate and dissociable processes. [ABSTRACT FROM AUTHOR]

Previous evidence suggests that alcohol affects various forms of temporal cognition. However, there are presently no studies investigating whether and how alcohol affects on time-based event expectations. Here, we investigated the effects of alcohol on time-based event expectations. Seventeen healthy volunteers, aged between 19 and 36 years, participated. We employed a variable foreperiod paradigm with temporally predictable events, mimicking a computer game. Error rate and reaction time were analyzed in placebo (0 g/kg), low dose (0.2 g/kg) and high dose (0.6 g/kg) conditions. We found that alcohol intake did not eliminate, but substantially reduced, the formation of time-based expectancy. This effect was stronger for high doses, than for low doses, of alcohol. As a result of our studies, we have evidence that alcohol intake impairs time-based event expectations. The mechanism by which the level of alcohol impairs time-based event expectations needs to be clarified by future research. [ABSTRACT FROM AUTHOR]

The involvement or noninvolvement of a clock-like neural process, an effector-independent representation of the time intervals to produce, is described as the essential difference between event-based and emergent timing. In a previous work (Bravi et al. in Exp Brain Res 232:1663-1675, . doi:), we studied repetitive isochronous wrist's flexion-extensions (IWFEs), performed while minimizing visual and tactile information, to clarify whether non-temporal and temporal characteristics of paced auditory stimuli affect the precision and accuracy of the rhythmic motor performance. Here, with the inclusion of new recordings, we expand the examination of the dataset described in our previous study to investigate whether simple and complex paced auditory stimuli (clicks and music) and their imaginations influence in a different way the timing mechanisms for repetitive IWFEs. Sets of IWFEs were analyzed by the windowed (lag one) autocorrelation-wγ(1), a statistical method recently introduced for the distinction between event-based and emergent timing. Our findings provide evidence that paced auditory information and its imagination favor the engagement of a clock-like neural process, and specifically that music, unlike clicks, lacks the power to elicit event-based timing, not counteracting the natural shift of wγ(1) toward positive values as frequency of movements increase. [ABSTRACT FROM AUTHOR]

Music performance requires precise control of limb movements in order to achieve temporal precision of performed tone onsets. Previous findings suggest that processes recruited for the temporal control of rhythmic body movements, such as those required in music performance, depend on the movement type (discrete vs. continuous) and the rate of the produced interonset intervals (sub-second vs. supra-second). Using a dual-task paradigm, the current study addressed these factors in the temporal control of cellists' bowing movements. Cellists performed melodies in a synchronization-continuation timing task at a specified fast (intertone interval = 700 ms) or slow (intertone interval = 1,100 ms) tempo with either discrete (staccato) or continuous (legato) bowing movements. A secondary working memory task involved a concurrent digit-switch counting task. Analyses of the produced tone durations showed that the working memory load significantly impaired temporal regularity when the melodies were performed with discrete bowing movements at the slower tempo. In addition, discrete movements led to more errors on the working memory task. These findings suggest that continuous body movements provide temporal control information to performers under high cognitive load conditions. [ABSTRACT FROM AUTHOR]

Humans are capable of learning a variety of motor skills such as playing the piano. Performance of these skills is subject to multiple constraints, such as musical phrasing or speed requirements, and these constraints vary from one context to another. In order to understand how the brain controls highly skilled movements, we investigated pianists playing musical scales with their left or right hand at various speeds. Pianists showed systematic temporal deviations away from regularity. At slow tempi, pianists slowed down at the beginning and end of the movement (which we call phrasal template). At fast tempi, temporal deviation traces consisted of three peak delays caused by a thumb-under manoeuvre (which we call neuromuscular template). Intermediate tempi were a linear combination trade-off between these two. We introduce and cross-validate a simple four-parameter model that predicted the timing deviation of each individual note across tempi ( R = 0.70). The model can be fitted on the data of individual pianists, providing a novel quantification of expert performance. The present study shows that the motor system can generate complex movements through a dynamic combination of simple movement templates. This provides insight into how the motor system flexibly adapts to varying contextual constraints. [ABSTRACT FROM AUTHOR]

The present study examined the development of a leader-follower relationship in joint action performed by participants with different skill levels. Two participants were instructed to produce discrete isometric forces such that the sum of the forces was the target force. The task did not prescribe the onset time or share of force each participant contributed to the target force. Although novices with low force variability did not produce an earlier force than those with high force variability in the novice-novice group, experienced participants produced an earlier force than novices in the novice-experienced group. While participants with low force variability always produced a stronger force than those with high force variability in both the groups, there was no significant difference in force distributions between participants with low and high force variabilities. Although a novice-experienced pair produced force more complementarily than a novice-novice pair in the first practice block, the difference between pairs vanished after the first practice block, suggesting that leader-follower relations were not always beneficial to task performance. In addition, practice of the joint action did not transfer to individual action. [ABSTRACT FROM AUTHOR]

The capacity for transcranial direct current stimulation (tDCS) to increase learning and cognition shows promise for the development of enhanced therapeutic interventions. One potential application is the combination of tDCS with cognitive training (CT), a psychological intervention which aims to improve targeted cognitive abilities. We have previously shown that tDCS enhanced performance accuracy, but not skill acquisition, on a dual n-back working memory (WM) CT task over repeated sessions. In the current study, we investigated the optimal timing for combining tDCS with the same CT task to enhance within and between session performance outcomes across two daily CT sessions. Twenty healthy participants received in a randomised order 30 min of anodal tDCS to the left dorsolateral prefrontal cortex immediately before ('offline' tDCS) and during performance ('online' tDCS) on a dual n-back WM CT task, in an intra-individual crossover design. Analyses examined within and between session consolidation effects of tDCS on CT performance outcomes. Results showed that 'online' tDCS was associated with better within session skill acquisition on the CT task, with a significant difference found between conditions the following day. These results suggest that 'online' tDCS is superior to 'offline' tDCS for enhancing skill acquisition when combining anodal tDCS with CT. This finding may assist with the development of enhanced protocols involving the combination of tDCS with CT and other rehabilitation protocols. [ABSTRACT FROM AUTHOR]

The human motor system quickly entrains rhythmic limb movement to the resonant frequency of mechanical systems with which it interacts, suggesting that entrainment to an appropriately designed training device might be a convenient way to teach desired movements. We tested this possibility by asking healthy subjects ( N = 30) to learn to move with a desired movement timing using a simple resonating arm training device: a lever attached to a manual wheelchair. The subjects tried to learn to roll the lever-driven wheelchair back and forth in place at a target frequency initially presented using a series of auditory beeps. One-third of the subjects trained without resonance and with no further feedback about rolling frequency; their performance did not improve. Another group trained with continual visual feedback of frequency error but no resonance; they quickly learned to roll the chair at the target frequency, as evidenced at both short-term and long-term (1 day later) retention tests. A third group trained with elastic bands attached to the lever that caused the system to resonate at the target frequency, providing a timing template. While these participants quickly entrained to the target frequency during training, they did not accurately reproduce this frequency when the system was no longer resonant, moving too slowly with the same systematic error at both the short-term and long-term retention tests. They also did not exhibit a timing aftereffect on the initial movements made when they transitioned from a resonant to non-resonant system or vice versa. This suggests they did not realize they were performing the task with a temporal error. Entrainment to mechanical resonance conveys usable information about movement timing, but seems to cause that movement timing to be perceived as slower than it actually is, as if a putative internal clock speeds up, which is a factor to consider in designing machine-assisted motor training. [ABSTRACT FROM AUTHOR]

This study represents the first systematic comparison of the relative contributions of auditory and visual feedback to sequence production. Participants learned an isochronous melody that they performed on a keyboard and attempted to perform this sequence at a prescribed rate while auditory and visual feedback were manipulated. Delayed auditory feedback (DAF) and delayed visual feedback (DVF) both tended to slow production of the sequence. These effects were additive. There was no modulation of this effect of delay in either modality by the absence of feedback in the other. In contrast with past research, DAF did not increase timing variability, though DVF did. Motion analyses ruled out differences in salience of visual feedback between delayed and non-delayed conditions as an explanation of the effects of DVF. The results suggest that the effects of delayed feedback may be attributable to both sensorimotor interference and to conflicting information across feedback channels. [ABSTRACT FROM AUTHOR]

Our perception of time is affected by the modality in which it is conveyed. Moreover, certain temporal phenomena appear to exist in only one modality. The perception of temporal regularity or structure (e.g., the 'beat') in rhythmic patterns is one such phenomenon: visual beat perception is rare. The modality-specificity for beat perception is puzzling, as the durations that comprise rhythmic patterns are much longer than the limits of visual temporal resolution. Moreover, the optimization that beat perception provides for memory of auditory sequences should be equally relevant to visual sequences. Why does beat perception appear to be modality specific? One possibility is that the nature of the visual stimulus plays a role. Previous studies have usually used brief stimuli (e.g., light flashes) to present visual rhythms. In the current study, a rotating line that appeared sequentially in different spatial orientations was used to present a visual rhythm. Discrimination accuracy for visual rhythms and auditory rhythms was compared for different types of rhythms. The rhythms either had a regular temporal structure that previously has been shown to induce beat perception in the auditory modality, or they had an irregular temporal structure without beat-inducing qualities. Overall, the visual rhythms were discriminated more poorly than the auditory rhythms. The beat-based structure, however, increased accuracy for visual as well as auditory rhythms. These results indicate that beat perception can occur in the visual modality and improve performance on a temporal discrimination task, when certain types of stimuli are used. [ABSTRACT FROM AUTHOR]

Debate exists as to whether humans use prospective or predictive control to intercept an object falling under gravity (Baurès et al. in Vis Res 47:2982-2991, ; Zago et al. in Vis Res 48:1532-1538, ). Prospective control involves using continuous information to regulate action. τ, the ratio of the size of the gap to the rate of gap closure, has been proposed as the information used in guiding interceptive actions prospectively (Lee in Ecol Psychol 10:221-250, ). This form of control is expected to generate movement modulation, where variability decreases over the course of an action based upon more accurate timing information. In contrast, predictive control assumes that a pre-programmed movement is triggered at an appropriate criterion timing variable. For a falling object it is commonly argued that an internal model of gravitational acceleration is used to predict the motion of the object and determine movement initiation. This form of control predicts fixed duration movements initiated at consistent time-to-contact (TTC), either across conditions (constant criterion operational timing) or within conditions (variable criterion operational timing). The current study sought to test predictive and prospective control hypotheses by disrupting continuous visual information of a falling ball and examining consistency in movement initiation and duration, and evidence for movement modulation. Participants ( n = 12) batted a ball dropped from three different heights (1, 1.3 and 1.5 m), under both full-vision and partial occlusion conditions. In the occlusion condition, only the initial ball drop and the final 200 ms of ball flight to the interception point could be observed. The initiation of the swing did not occur at a consistent TTC, τ, or any other timing variable across drop heights, in contrast with previous research. However, movement onset was not impacted by occluding the ball flight for 280-380 ms. This finding indicates that humans did not need to be continuously coupled to vision of the ball to initiate the swing accurately, but instead could use predictive control based on acceleration timing information (TTC2). However, other results provide evidence for movement modulation, a characteristic of prospective control. Strong correlations between movement initiation and duration and reduced timing variability from swing onset to arrival at the interception point, both support compensatory variability. An analysis of modulation within the swing revealed that early in the swing, the movement acceleration was strongly correlated to the required mean velocity at swing onset and that later in the swing, the movement acceleration was again strongly correlated with the current required mean velocity. Rather than a consistent movement initiated at the same time, these findings show that the swing was variable but modulated for meeting the demands of each trial. A prospective model of coupling τ with τ was found to provide a very strong linear fit for an average of 69% of the movement duration. These findings provide evidence for predictive control based on TTC2 information in initiating the swing and prospective control based on τ in guiding the bat to intercept the ball. [ABSTRACT FROM AUTHOR]

Temporal binding (TB) refers to a subjective contraction of the time that elapses between an action and a delayed sensory consequence of it. The TB effect has been demonstrated primarily in tasks in which a key press triggers a tone after a short delay and in which participants judge the timing of one or both of these events relative to a visual reference (e.g., a rotating clock hand). In the present Experiments 1 and 2, musicians listened instead to an auditory 'clock' (a metronome) and occasionally made a tap that triggered a delayed tone. The task was to judge whether that test tone fell before, on, or after the midpoint of the interval between two metronome tones. In a passive control condition, participants judged test tones but did not tap. The hypothesis was that the test tone would be perceived as occurring earlier in the active than in the passive condition. However, there was no difference in perceptual judgments. Experiment 3 used a visual metronome as the reference but again obtained negative results, despite greater uncertainty of judgments. It is suggested that TB of action consequences to actions does not occur when the reference signal is rhythmic because such a context enables participants (musicians, at least) to perceive and judge the actual time of occurrence of the action-triggered tone. [ABSTRACT FROM AUTHOR]

Intelligence is associated with accuracy in a wide range of timing tasks. One source of such associations is likely to be individual differences in top-down control, e.g., sustained attention, that influence performance in both temporal tasks and other cognitively controlled behaviours. In addition, we have studied relations between intelligence and a simple rhythmic motor task, isochronous serial interval production (ISIP), and found a substantial component of that relation, which is independent of fluctuations in top-down control. The main purpose of the present study was to investigate whether such bottom-up mechanisms are involved also in the relation between intelligence and reaction time (RT) tasks. We thus investigated whether common variance between the ISIP and RT tasks underlies their respective associations with intelligence. Two hundred and twelve participants performed a simple RT task, a choice RT task and the ISIP task. Intelligence was assessed with the Raven SPM Plus. The analysed timing variables included mean and variability in the RT tasks and two variance components in the ISIP task. As predicted, RT and ISIP variables were associated with intelligence. The timing variables were positively intercorrelated, and a principal component analysis revealed a substantial first principal component that was strongly related to all timing variables, and positively correlated with intelligence. Furthermore, a commonality analysis demonstrated that the relations between intelligence and the timing variables involved a commonality between the timing variables as well as unique contributions from choice RT and ISIP. We discuss possible implications of these findings and argue that they support our main hypothesis, i.e., that relations between intelligence and RT tasks have a bottom-up component. [ABSTRACT FROM AUTHOR]

Temporal and spatial information are necessary when pointing to touch moving objects at a specific location. Here, we introduce an interception paradigm that allows us to uncorrelate spatial and temporal errors so that subjects did not have to trade one for the other. We showed the initial trajectories of two objects that moved (laterally or sagittally) with random presentation times and speeds along a collision path. Subjects had to point manually to the collision place at the correct time. We found better temporal accuracy when hand movements matched the motion target direction (e.g., the hand sagittally pointed to a collision point defined along a sagittal trajectory). This temporal selectivity disappeared when subjects had to judge the collision time responding with a single press. The results point to a contribution of proprioceptive information of hand velocity in reducing the temporal uncertainty in a temporal coincidence task. [ABSTRACT FROM AUTHOR]

We examined the hypothesis that developmental coordination disorder (DCD) consists of a poor integration of distal preparatory visual information with the visual information that arises during movement execution. We set up a steering task where the action goal was to steer smoothly on a virtual winding course under conditions that manipulated the availability and timing of visual information. Participants were 20 young adults who had been diagnosed with DCD in their childhood and 20 typically developing age-matched controls. On a simple tracking task, participants with DCD were slower and more variable than controls. The group differences dissipated, however, when the display highlighted the directional changes necessary within the next 500 ms. When the latter condition was modified to also include the full layout of the course, however, the performance of the DCD group once again decreased. This result could not be attributed to a simple distraction effect. The results suggest that distinct neural mechanisms are associated with the processing of fast visual information for online control and longer-term action preparation based on spatial layout. In skilled action, cerebellar and parietal areas process information effectively and their outputs are integrated into one smooth movement. Because the DCD group showed difficulties in steering when both types of information were present, it is likely that this integration is suboptimal. [ABSTRACT FROM AUTHOR]

Many interceptive actions involve interactions with objects that are familiar to the observer and have known sizes. Two experiments investigated how known size influences observers’ perception of time-to-contact ( Tc). Participants made Tc judgements of objects that were either ambiguously sized, standard-size in identity/familiarity, or off-size in identity/familiarity, and simulated as approaching on linear trajectories (Experiment 1), or linear versus parabolic trajectories (Experiment 2). In Experiment 1, Tc judgements were influenced by the size of the object in the three object identity/familiarity conditions; the greatest size effect occurred in the off-size condition compared to the ambiguous size and standard-size conditions. The results of Experiment 2 replicated these results and found that size effects were not reduced with displays simulating parabolic trajectories, that is, displays simulating ecologically valid free-falling objects. Taken together, the finding that Tc judgements are influenced by object identity/familiarity does not provide support for the tau hypothesis, nor the hypothesis that Tc judgements are based solely on optic expansion rates. However, the results do provide support for the proposition that Tc judgements are based on a combination of rate of retinal image expansion and object identity/familiarity information, the latter information requiring observers to have prior experience with, or knowledge about, the objects. [ABSTRACT FROM AUTHOR]

While much is known about sequential effects in motor timing, less is understood about whether movement parameters such as force show sequential dependencies. In this study, we examined the effect of timing constraints on repetitive unimanual force production sequences. Ten healthy participants produced a series of pinch grip forces in time to a metronome and to visually specified force amplitudes. Either visual feedback of force produced or the auditory metronome removed 10 s into the experimental trial, with participants performing continued responses for the remaining 20 s. In the continuation trials, a negative lag-1 autocorrelation in the inter-response intervals (IRIs) was observed as is commonly seen in motor timing tasks. However, removal of visual feedback resulted in a systematic increase in mean force output through the course of the trial, resulting in positive lag-1 autocorrelation values. An interaction was found between mean IRI and peak force (PF) magnitude, with greater force variability seen for the larger intervals. However, the imposition of dual force and timing constraints had no effect either on the underlying variability of the PF or on the IRIs. The results are discussed in the context of force and time being independently specified components of a generalized motor program. [ABSTRACT FROM AUTHOR]

Structural changes of the cerebellum have been reported in several psychiatric diseases like schizophrenia, autism and attention-deficit/hyperactivity disorder (ADHD). Beside behavioral deficits children with ADHD often show slight motor abnormalities. Cerebellar malfunction may contribute. The cerebellum is a structure essential for motor coordination, various forms of motor learning and timing of motor responses. In the present study, eyeblink conditioning was applied to investigate learning and timing of motor responses both in children with ADHD and children with cerebellar lesions. Acquisition, timing and extinction of conditioned eyeblink responses were investigated in children with ADHD, children with chronic surgical cerebellar lesions and controls using a standard delay paradigm with two different interstimulus intervals. Timing of conditioned eyeblink responses was significantly impaired in children with ADHD in the long interstimulus interval condition. Also in children with cerebellar lesions conditioned responses (CR) tended to occur earlier than in controls. Incidences of CRs were significantly reduced in children with cerebellar lesions and tended to be less in children with ADHD than in controls. Extinction of the CRs was impaired in children with cerebellar lesions in both interstimulus interval conditions and in children with ADHD in the long interstimulus interval condition. Cerebellar malfunction may contribute to disordered eyeblink conditioning in ADHD. However, because CR abnormalities differed between ADHD and cerebellar subjects, dysfunction of non-cerebellar structures cannot be excluded. [ABSTRACT FROM AUTHOR]

To account for sensorimotor synchronization, the information processing and the dynamical systems perspectives have developed different classes of models. While the former has focused on cycle-to-cycle correction of the timing errors, the latter deals with a continuous, state-dependent within-cycle coupling between the oscillating limb and the metronome. The purpose of the present study was to investigate the extent to which the two modeling frameworks partially capture the same behavior or, instead, account for different aspects of synchronization. A comparative two-level analysis (time intervals and movement trajectories) of synchronized tapping and synchronized oscillation data revealed distinct patterns of results with regard to (1) the relationship between the (a)symmetry of movement cycles and the achievement of timing goals, and (2) the sequential or within-cycle organization of synchronization processes. Our results support the idea that movement trajectories contribute to the achievement of synchronized movement timing in two different ways as a function of the (dis)continuous nature of movement. We suggest that the two modeling frameworks indeed account for different synchronization processes involved in the process of keeping time with the beat. [ABSTRACT FROM AUTHOR]

This article investigated both the ability of naive human subjects to learn interval production, as well as the properties of learning generalization across modalities and interval durations that varied systematically from the over-trained interval. Human subjects trained on a 450-, 650-, or 850-ms single-interval production task, using auditory stimuli to define the intervals, showed a significant decrease in performance variability with intensive training. This learning generalized to the visual modality and to non-trained durations following a Gaussian transfer pattern. However, the learning carryover followed different rules, depending on the duration of the trained interval as follows: (1) the dispersion of the generalization curve increased as a function of the trained interval, (2) the generalization pattern was tilted to the right in the visual condition, and (3) the transfer magnitude for 650 ms was less prominent than for the other two intervals. These findings suggest the existence of neural circuits that are tuned to specific time lengths and that show different temporal processing properties depending on their preferred interval duration. [ABSTRACT FROM AUTHOR]

For synchronous bimanual movements, we have shown that a different amplitude can be prepared for each limb in advance and this preparation improves with practice (Maslovat et al. ). In the present study, we tested whether an asynchronous bimanual movement can also be prepared in advance and be improved with practice. Participants practiced (160 trials) a discrete bimanual movement in which the right arm led the left by 100 ms in response to an auditory “go” signal (either 80 dB control stimulus or 124 dB startle stimulus). The startle stimulus was used to gauge whether inter-limb timing could be pre-programed. During startle trials, the asynchronous bimanual movement was triggered at early latency suggesting the entire movement could be prepared in advance. However, the triggered movement had a shorter between-arm delay and a temporally compressed within-arm EMG pattern, results that we attribute to increased neural activation caused by the startling stimulus. However, as both startle and control trials improved over time, it does appear response preparation of interval timing can improve with practice. [ABSTRACT FROM AUTHOR]

In order to successfully intercept a moving target one must be at the right place at the right time. But simply being there is seldom enough. One usually needs to make contact in a certain manner, for instance to hit the target in a certain direction. How this is best achieved depends on the exact task, but to get an idea of what factors may limit performance we asked people to hit a moving virtual disk through a virtual goal, and analysed the spatial and temporal variability in the way in which they did so. We estimated that for our task the standard deviations in timing and spatial accuracy are about 20 ms and 5 mm. Additional variability arises from individual movements being planned slightly differently and being adjusted during execution. We argue that the way that our subjects moved was precisely tailored to the task demands, and that the movement accuracy is not only limited by the muscles and their activation, but also—and probably even mainly—by the resolution of visual perception. [ABSTRACT FROM AUTHOR]

Long-range dependence is a characteristic property of successively produced time intervals, such as in un-paced or continuation tapping. We hypothesise in the present paper that serial dependence in such tasks could be related to a closed-loop regulation process, in which the current interval is determined by preceding ones. As a consequence, the quality of sensory feedback is likely to affect serial dependence. An experiment with human participants shows that diminished sensory information tends to increase the Hurst exponent for short inter-onset intervals and tends to decrease it for long intervals. A simulation shows that a simple auto-regressive model, whose order depends on the ratio between the inter-onset interval and an assumed temporal integration span, is able to account for most of our empirical results, including the duration specificity of long-range correlation. [ABSTRACT FROM AUTHOR]

Intercepting and avoiding collisions with moving objects are fundamental skills in daily life. Anticipatory behavior is required because of significant delays in transforming sensory information about target and body motion into a timed motor response. The ability to predict the kinematics and kinetics of interception or avoidance hundreds of milliseconds before the event may depend on several different sources of information and on different strategies of sensory-motor coordination. What are exactly the sources of spatio-temporal information and what are the control strategies remain controversial issues. Indeed, these topics have been the battlefield of contrasting views on how the brain interprets visual information to guide movement. Here we attempt a synthetic overview of the vast literature on interception. We discuss in detail the behavioral and neurophysiological aspects of interception of targets falling under gravity, as this topic has received special attention in recent years. We show that visual cues alone are insufficient to predict the time and place of interception or avoidance, and they need to be supplemented by prior knowledge (or internal models) about several features of the dynamic interaction with the moving object. [ABSTRACT FROM AUTHOR]

Synchronising our actions with external events is a task we perform without apparent effort. Its foundation relies on accurate temporal control that is widely accepted to take one of two different modes of implementation: explicit timing for discrete actions and implicit timing for smooth continuous movements. Here we assess synchronisation performance for different types of action and test the degree to which each action supports corrective updating following changes in the environment. Participants performed three different finger actions in time with an auditory pacing stimulus allowing us to assess synchronisation performance. Presenting a single perturbation to the otherwise regular metronome allowed us to examine corrections supported by movements varying in their mode of timing implementation. We find that discrete actions are less variable and support faster error correction. As such, discrete actions may be preferred when engaging in time-critical adaptive behaviour with people and objects in a dynamic environment. [ABSTRACT FROM AUTHOR]

The Wing–Kristofferson (WK) model of movement timing emphasises the separation of central timer and motor processes. Several studies of repetitive timing have shown that increase in variability at longer intervals is attributable to timer processes; however, relatively little is known about the way motor aspects of timing are affected by task movement constraints. In the present study, we examined timing variability in finger tapping with differences in interval to assess central timer effects, and with differences in movement amplitude to assess motor implementation effects. Then, we investigated whether effects of motor timing observed at the point of response (flexion offset/tap) are also evident in extension, which would suggest that both phases are subject to timing control. Eleven participants performed bimanual simultaneous tapping, at two target intervals (400, 600 ms) with the index finger of each hand performing movements of equal (3 or 6 cm) or unequal amplitude (left hand 3, right hand 6 cm and vice versa). As expected, timer variability increased with the mean interval but showed only small, non-systematic effects with changes in movement amplitude. Motor implementation variability was greater in unequal amplitude conditions. The same pattern of motor variability was observed both at flexion and extension phases of movement. These results suggest that intervals are generated by a central timer, triggering a series of events at the motor output level including flexion and the following extension, which are explicitly represented in the timing system. [ABSTRACT FROM AUTHOR]

The ability to precisely time events is essential for both perception and action. There is evidence that the cerebellum is important for the neural representation of time in a variety of behaviors including time perception, the tapping of specific time intervals, and eye-blink conditioning. It has been difficult to assess the contribution of the cerebellum to timing during more dynamic motor behavior because the component movements themselves may be abnormal or any motor deficit may be due to an inability to combine the component movements into a complete action rather than timing per se. Here we investigated the performance of subjects with cerebellar disease in predictive motor timing using a task that involved mediated interception of a moving target, and we tested the effect of movement type (acceleration, deceleration, constant), speed (slow, medium, fast), and angle (0°, 15° and 30°) on performance. The subjects with cerebellar damage were significantly worse at interception than healthy controls even when we controlled for basic motor impairments such as response time. Our data suggest that subjects with damage to the cerebellum have a fundamental problem with predictive motor timing and indicate that the cerebellum plays an essential role in integrating incoming visual information with motor output when making predictions about upcoming actions. The findings demonstrate that the cerebellum may have properties that would facilitate the processing or storage of internal models of motor behavior. [ABSTRACT FROM AUTHOR]

Time processing is important in several cognitive and motor functions, but it is still unclear how the human brain perceives time intervals of different durations. Processing of time in millisecond and second intervals may depend on different neural networks and there is now considerable evidence to suggest that these intervals are possibly measured by independent brain mechanisms. Using repetitive transcranial magnetic stimulation (rTMS), we determined that the cerebellum is essential in explicit temporal processing of millisecond time intervals. In the first experiment, subjects’ performance in a time reproduction task of short (400–600 ms) and long (1,600–2,400 ms) intervals, were evaluated immediately after application of inhibitory rTMS trains over the left and right lateral cerebellum (Cb) and the right dorsolateral prefrontal cortex (DLPFC). We found that rTMS over the lateral cerebellum impaired time perception in the short interval (millisecond range) only; for the second range intervals, impaired timing was found selectively for stimulation of the right DLPFC. In the second experiment, we observed that cerebellar involvement in millisecond time processing was evident when the time intervals were encoded but not when they were retrieved from memory. Our results are consistent with the hypothesis that the cerebellum can be considered as an internal timing system, deputed to assess millisecond time intervals. [ABSTRACT FROM AUTHOR]

Movement sequences such as typing or tapping display important interactions among finger movements arising from anticipatory motion (preparing for upcoming events) and coupling (non-independence among fingers). We examined pianists’ finger tapping for the influence of cognitive chunking processes and biomechanical coupling constraints. In a synchronization-continuation task, pianists repeatedly tapped four-finger sequences that differed in terms of the chunks that formed subsequences and in the transitions among physically adjacent or non-adjacent fingers. Chunking influenced intertap intervals, regardless of the particular fingers tapped; the final tap of each chunk was lengthened and less variable relative to other taps. The particular fingers tapped influenced peak finger heights, consistency of motion, and velocity–acceleration patterns, regardless of chunking. Thus, cognitive constraints influenced timing, whereas biomechanical factors influenced motion trajectories. These findings provide an important caveat for study of anticipatory motion by documenting the influence of biomechanical coupling on motion trajectories. [ABSTRACT FROM AUTHOR]

In right-handed subjects the execution of a simple finger-tapping task is associated with an asymmetry of interhemispheric interaction, probably suggesting that the dominant left hemisphere inhibits the right one. The present study investigated the left-handed subjects in order to elucidate whether this asymmetry is related to handedness. Nineteen healthy subjects performed unimanual left, right, and bimanual auditorily paced finger-tapping tasks while neuromagnetic activity was recorded with a 122-channel whole-head neuromagnetometer (MEG). Simultaneously, we recorded activity of the first dorsal interosseus (FDI) muscle of both hands. By using the analysis tool dynamic imaging of coherent sources (DICS), oscillatory activity at alpha as well as at beta frequency within the primary sensorimotor (S1/M1) and premotor (PMC) cortex was localized. As expected, we observed oscillatory coupling between S1/M1 and PMC contralateral to the moving hand. Furthermore, coupling between left PMC and bilateral S1/M1 occurred in each movement condition, suggesting that the left PMC modulates neural activity in bilateral primary sensorimotor cortices independent of the moving hand. Coupling between bilateral S1/M1 occurred more frequently and significantly stronger during the right hand condition. This result demonstrates the same interhemispheric coupling pattern as in right-handed subjects, suggesting that the asymmetry of this interaction is not due to hand dominance. A specialization of the left premotor cortex either for superior motor control per se or for the execution of sequential tasks might account for these results. [ABSTRACT FROM AUTHOR]

The results of two experiments are reported that examined how performance in a simple interceptive action (hitting a moving target) was influenced by the speed of the target, the size of the intercepting effector and the distance moved to make the interception. In Experiment 1, target speed and the width of the intercepting manipulandum (bat) were varied. The hypothesis that people make briefer movements, when the temporal accuracy and precision demands of the task are high, predicts that bat width and target speed will divisively interact in their effect on movement time (MT) and that shorter MTs will be associated with a smaller temporal variable error (VE). An alternative hypothesis that people initiate movement when the rate of expansion (ROE) of the target’s image reaches a specific, fixed criterion value predicts that bat width will have no effect on MT. The results supported the first hypothesis: a statistically reliable interaction of the predicted form was obtained and the temporal VE was smaller for briefer movements. In Experiment 2, distance to move and target speed were varied. MT increased in direct proportion to distance and there was a divisive interaction between distance and speed; as in Experiment 1, temporal VE was smaller for briefer movements. The pattern of results could not be explained by the strategy of initiating movement at a fixed value of the ROE or at a fixed value of any other perceptual variable potentially available for initiating movement. It is argued that the results support pre-programming of MT with movement initiated when the target’s time to arrival at the interception location reaches a criterion value that is matched to the pre-programmed MT. The data supported completely open-loop control when MT was less than between 200 and 240 ms with corrective sub-movements increasingly frequent for movements of longer duration. [ABSTRACT FROM AUTHOR]