Event-based Timing Research Articles

Interlimb Coordination and Auditory-Motor Synchronization in Children with Developmental Coordination Disorder: Examining Antiphase Knee Movements with Auditory Metronomes While Seated.

Background: Children with developmental coordination disorder (DCD) exhibit reduced interlimb coordination compared to typically developing children (TDC) during complex tasks like running, which requires dynamic postural control. However, the extent of interlimb coordination difficulties in DCD during tasks that demand minimal dynamic balance, such as self-paced and externally auditory-paced tasks, remains unclear. This study aimed to compare interlimb coordination and auditory-motor synchronization between children with DCD and TDC during a seated antiphase coordination task of the lower limbs, which has minimal postural control requirements. Methods: Twenty-one children with DCD and 22 TDC performed an antiphase knee flexion and extension task while seated, in three conditions (baseline silence, metronome discrete, and metronome continuous), for three minutes. The interlimb coordination, synchronization, and spatiotemporal movement parameters were analyzed using a mixed model analysis; Results: Children with DCD displayed less coordinated interlimb movements compared to TDC (p = 0.0140), which was the result of the greater variability in coordinating antiphase knee flexion-extension movements (p < 0.0001). No group differences in spatiotemporal movement parameters were observed. Children with DCD, compared to TDC, had a lower synchronization consistency to metronomes (p = 0.0155). Discrete metronomes enhanced interlimb coordination compared to the baseline silence condition (p = 0.0046); Conclusions: The study highlights an inferior interlimb coordination and auditory-motor synchronization in children with DCD compared to TDC. Implementing metronomes with a discrete temporal structure improved the interlimb coordination of both groups during the used fundamental seated interlimb coordination task, supporting theorical frameworks of event-based timing.

A CMOS AFE With 37-nA rms Input-Referred Noise and Marked 96-dB Timing DR for Pulsed LiDAR

This paper presents an analog front-end (AFE) circuit with marked timing point for pulsed time-of-flight LiDAR that employs either sampling- or event-based timing approach. The proposed AFE adopts a dual-mode structure for its pre-amplifier which can be configured as a charge-sensitive amplifier (CSA) or a gated active load-assisted TIA (GALA-TIA), depending on the intensity of input current. As a result, both the sensitivity and dynamic range (DR) of the AFE have been effectively improved. In addition, the zero-crossing point of the output signal has been marked as the timing point with a built-in pulse shaper, which allows the back-end circuits of LiDAR receiver discriminate the timing conveniently and accurately. The measured input-referred RMS noise current of the proposed AFE is 37 nA. With dual-mode control, a linear output DR of 80 dB and a wide timing DR of 96 dB with walk error no more than ±160 ps have been achieved. For single-shot measurement application, only CSA mode was enabled and the pulse widths of saturated output signals have been measured to compensate the walk errors, which realized a timing DR of 78 dB with accuracy of ±150 ps. The averaged power consumption is 66 mW and the total silicon area is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.79\times 0.42\,\,mm^{2}$ </tex-math></inline-formula> in 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS process.

The design of HEPS global timing system

The high energy photon source (HEPS) is a 4th generation synchrotron light source under construction by the institute of high energy physics. The accelerator complex consists of a 500-MeV Linac, a full-energy synchrotron booster, a 6-GeV synchrotron storage ring (SR), and three e-beam transport lines for injection and extraction among accelerators. A global timing system (GTS) covers the timing needs for all accelerator, beamline, and experiment systems. The GTS is designed to coordinate the injection processes and various measurements and protections. Most systems require that the RMS jitter of the GTS signal is less than 30 ps, while the trigger jitters for the electron gun and SR injection and extraction kickers are less than 10 ps. The HEPS GTS is an event-based timing system based on MicroTCA.4 hardware architecture. The MicroTCA.4 300 series products from the micro-research Finland Oy are implemented in the HEPS GTS system. The RMS jitter, integrated from 1 Hz to 10 MHz, of the 166.6 MHz event clock is 5.489 ps. The RMS jitter of TTL outputs is less than 30 ps. This paper reports the design of the HEPS GTS, which satisfies all of the HEPS physics requirements for timing with preliminary test results shown.

Technique research of event-based timing system

Background The timing system of BEPC-II is established based on event generator and event receiver (EVR) modules from the Micro-Research Finland. Though it works smoothly, there are some downsides; for example, the output pulses cannot be adjusted in picosecond accuracy in EVRs, and additional hardware modules besides EVR had to be developed to generate the revolution frequency of synchrotron radiation ring of BEPC-II.

Quantifying land use influences on event-based flow frequency, timing, magnitude, and rate of change in an urbanizing watershed of the central USA

There is a need for research that advances understanding of flow alterations in contemporary watersheds where natural and anthropogenic interactions can confound mitigation efforts. Event-based flow frequency, timing, magnitude, and rate of change were quantified at five-site nested gauging sites in a representative mixed-land-use watershed of the central USA. Statistically independent storms were paired by site (n = 111 × 5 sites) to test for significant differences in event-based rainfall and flow response variables (n = 17) between gauging sites. Increased frequency of small peak flow events (i.e., 64 more events less than 4.0 m3 s−1) was observed at the rural–urban interface of the watershed. Differences in flow response were apparent during drier periods when small rainfall events resulted in increased flow response at urban sites in the lower reaches. Relationships between rainfall and peak flow were stronger with decreased pasture/crop land use and increased urban land use by approximately 20%. Event-based total rainfall explained 40–68% of the variance in peak flow (p < 0.001). Coefficients of determination (r2) were negatively correlated with pasture/crop land use (r2 = 0.92; p = 0.007; n = 5) and positively correlated with urban land use (r2 = 0.90; p = 0.008; n = 5). Significant differences in flow metrics were observed between rural and urban sites (p < 0.05; n = 111) that were not explained by differences in rainfall variables and drainage area. An urban influence on flow timing was observed using median time lag to peak centroid and time of maximum precipitation to peak flow. Results highlight the need to establish manageable flow targets in rapidly urbanizing mixed-land-use watersheds.

Timestamp Temporal Logic (TTL) for Testing the Timing of Cyber-Physical Systems

In order to test the performance and verify the correctness of Cyber-Physical Systems (CPS), the timing constraints on the system behavior must be met. Signal Temporal Logic (STL) can efficiently and succinctly capture the timing constraints of a given system model. However, many timing constraints on CPS are more naturally expressed in terms of events on signals. While it is possible to specify event-based timing constraints in STL, such statements can quickly become long and arcane in even simple systems. Timing constraints for CPS, which can be large and complex systems, are often associated with tolerances, the expression of which can make the timing constraints even more cumbersome using STL. This paper proposes a new logic, Timestamp Temporal Logic (TTL), to provide a definitional extension of STL that more intuitively expresses the timing constraints of distributed CPS. TTL also allows for a more natural expression of timing tolerances. Additionally, this paper outlines a methodology to automatically generate logic code and programs to monitor the expressed timing constraints. Since our TTL monitoring logic evaluates the timing constraints using only the timestamps of the required events on the signal, the TTL monitoring logic has significantly less memory footprint when compared to traditional STL monitoring logic, which stores the signal value at the required sampling frequency. The key contribution of this paper is a scalable approach for online monitoring of the timing constraints. We demonstrate the capabilities of TTL and our methodology for online monitoring of TTL constraints on two case studies: 1) Synchronization and phase control of two generators and, 2) Simultaneous image capture using distributed cameras for 3D image reconstruction.

Testing the co-existence of two timing strategies for motor control in a unique task: The synchronisation spatial-tapping task

The control of rhythmic action sequences may involve two distinct timing strategies, i.e., event-based and emergent timing, which are usually revealed through finger-tapping and circle-drawing tasks, respectively. There is a lively debate concerning the possibility of coexistence of the two modes of timing for the execution of a single task. If one considers emergent timing as simply an absence of explicit representation of a time interval, then by definition, the two modes of timing cannot coexist. However, if one considers that emergent timing engages control of another motor parameter, e.g., a control of movement through space rather than time, then the possibility of coexistence needs to be reassessed. In the present study, we designed a hybrid of finger-tapping and circle-drawing tasks for which the demands for space and time control were present at the same time in order to reassess the coexistence hypothesis. Seventy-eight participants performed a spatial-tapping task in which finger taps were to be produced in synchrony with a regular metronome to 6 visual targets presented around a virtual circle. The metronome set ten distinct tempi (1100–300ms). Using autocorrelation analyses on timing variables, we show that motor timing was event-based at slow tempi and emergent at faster tempi. Through an analysis of the trajectory, we confirm that an increase in the spatial control of movement took place congruently with a switch from event-based to emergent timing modes. At these fast tempi, timing and spatial errors were correlated but only at the specific target location for which a dynamical anchor point was revealed. Hence, we conclude that the coding of emergent timing has a spatial nature from which emerge timing regularities. This spatio-temporal strategy insures the performance of sequential motor actions when cognitive effort is too high for the use of pure event-based timing strategies.

High-Throughput Logic Timing Simulation on GPGPUs

Many EDA tasks such as test set characterization or the precise estimation of power consumption, power droop and temperature development, require a very large number of time-aware gate-level logic simulations. Until now, such characterizations have been feasible only for rather small designs or with reduced precision due to the high computational demands. The new simulation system presented here is able to accelerate such tasks by more than two orders of magnitude and provides for the first time fast and comprehensive timing simulations for industrial-sized designs. Hazards, pulse-filtering, and pin-to-pin delay are supported for the first time in a GPGPU accelerated simulator, and the system can easily be extended to even more realistic delay models and further applications. A sophisticated mapping with efficient memory utilization and access patterns as well as minimal synchronizations and control flow divergence is able to use the full potential of GPGPU architectures. To provide such a mapping, we combine for the first time the versatility of event-based timing simulation and multi-dimensional parallelism used in GPU-based gate-level simulators. The result is a throughput-optimized timing simulation algorithm, which runs many simulation instances in parallel and at the same time fully exploits gate-parallelism within the circuit.

Music, clicks, and their imaginations favor differently the event-based timing component for rhythmic movements.

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, 2014a. doi: 10.1007/s00221-014-3845-9 ), 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.

Wide dynamic range FPGA-based TDC for monitoring a trigger timing distribution system in linear accelerators

A new field-programmable gate array (FPGA)-based time-to-digital converter (TDC) with a wide dynamic range greater than 20ms has been developed to monitor the timing of various pulsed devices in the trigger timing distribution system of the KEKB injector linac for the Super KEK B-factory project. The pulsed devices are driven by feeding regular as well as any irregular (or event-based) timing pulses. The timing pulses are distributed to these pulsed devices along the linac beam line with fiber-optic links on the basis of the parameters to be set pulse-by-pulse in the event-based timing and control system within 20ms. For monitoring the timing as precisely as possible, a 16-ch FPGA-based TDC has been developed on a Xilinx Spartan-6 FPGA equipped on VME board with a resolution of 1ns. The resolution was achieved by applying a multisampling technique, and the accuracies were 2.6ns (rms) and less than 1ns (rms) within the dynamic ranges of 20ms and 7.5ms, respectively. The various nonlinear effects were improved by implementing a high-precision external clock with a built-in temperature-compensated crystal oscillator.

A little elastic for a better performance: kinesiotaping of the motor effector modulates neural mechanisms for rhythmic movements.

A rhythmic motor performance is brought about by an integration of timing information with movements. Investigations on the millisecond time scale distinguish two forms of time control, event-based timing and emergent timing. While event-based timing asserts the existence of a central internal timekeeper for the control of repetitive movements, the emergent timing perspective claims that timing emerges from dynamic control of nontemporal movements parameters. We have recently demonstrated that the precision of an isochronous performance, defined as performance of repeated movements having a uniform duration, was insensible to auditory stimuli of various characteristics (Bravi et al., 2014). Such finding has led us to investigate whether the application of an elastic therapeutic tape (Kinesio® Tex taping; KTT) used for treating athletic injuries and a variety of physical disorders, is able to reduce the timing variability of repetitive rhythmic movement. Young healthy subjects, tested with and without KTT, have participated in sessions in which sets of repeated isochronous wrist's flexion-extensions (IWFEs) were performed under various auditory conditions and during their recall. Kinematics was recorded and temporal parameters were extracted and analyzed. Our results show that the application of KTT decreases the variability of rhythmic movements by a 2-fold effect: on the one hand KTT provides extra proprioceptive information activating cutaneous mechanoreceptors, on the other KTT biases toward the emergent timing thus modulating the processes for rhythmic movements. Therefore, KTT appears able to render movements less audio dependent by relieving, at least partially, the central structures from time control and making available more resources for an augmented performance.

The Influence of Robotic Guidance on Different Types of Motor Timing

ABSTRACT Robotic guidance as a means to facilitate motor learning and rehabilitation has received considerable attention during the last few years. However, mixed outcomes suggest that the benefits might be restricted to certain movement characteristics. The authors investigate the effects of robotic guidance on different kinds of motor timing. Two groups of participants performed 2 variants of a circle drawing task in a synchronization-continuation paradigm. One variant was continuous circle drawing (emergent timing), the other variant was intermittent circle drawing (event-based timing). The total duration of movement cycles (absolute timing) and the relative duration of submovements (relative timing) were measured. Half of the participants in each group were guided by a robot device during synchronization (robot-guided group), the other half of the participants received no guidance (control group). Guided participants had superior performance during the synchronization phase with both timing tasks. During continuation there were no benefits of haptic guidance anymore with the continuous circle drawing task. In contrast, with the intermittent circle drawing task guided participants were more accurate in their relative timing than control participants already in the first few trials, and this advantage did not increase in the course of practice. The benefit is thus rather immediate and not cumulative. This finding is consistent with the notion that movement characteristics such as relative timing, which are hard to demonstrate visually or verbally, profit from robotic guidance because of the more accurate demonstrations of the correct movements.

The KEKB injector linac

The KEKB injector linac has been continuously improved to enhance the stability of many devices and the efficiency of beam operation. These improvements include the development of the new C-band accelerating structure, pulse compressor, klystron, rf window, compact modulator, and the new positron production target using crystalline tungsten. We have also achieved two-bunch beam acceleration, the development of an energy spread monitor, a safety system upgrade, and an event-based timing and control system. These developments and practical applications for advanced linac beam handling result in the success of the simultaneous top-up injection among the three independent storage rings. This result greatly improves the integrated luminosity and the operation stability of the KEKB rings. In this paper, we present the progress of the KEKB injector linac in this decade.

The role of musical training in emergent and event-based timing

Introduction: Musical performance is thought to rely predominantly on event-based timing involving a clock-like neural process and an explicit internal representation of the time interval. Some aspects of musical performance may rely on emergent timing, which is established through the optimization of movement kinematics, and can be maintained without reference to any explicit representation of the time interval. We predicted that musical training would have its largest effect on event-based timing, supporting the dissociability of these timing processes and the dominance of event-based timing in musical performance.Materials and Methods: We compared 22 musicians and 17 non-musicians on the prototypical event-based timing task of finger tapping and on the typically emergently timed task of circle drawing. For each task, participants first responded in synchrony with a metronome (Paced) and then responded at the same rate without the metronome (Unpaced).Results: Analyses of the Unpaced phase revealed that non-musicians were more variable in their inter-response intervals for finger tapping compared to circle drawing. Musicians did not differ between the two tasks. Between groups, non-musicians were more variable than musicians for tapping but not for drawing. We were able to show that the differences were due to less timer variability in musicians on the tapping task. Correlational analyses of movement jerk and inter-response interval variability revealed a negative association for tapping and a positive association for drawing in non-musicians only.Discussion: These results suggest that musical training affects temporal variability in tapping but not drawing. Additionally, musicians and non-musicians may be employing different movement strategies to maintain accurate timing in the two tasks. These findings add to our understanding of how musical training affects timing and support the dissociability of event-based and emergent timing modes.

Aging effects on event and emergent timing in bimanual coordination

There is growing evidence that normal aging may produce declines in some motor tasks but not others. One account of the task-specific aging effects suggests that age-related differences will be evident in tasks that demand high-level processing but not in tasks that can be performed relatively automatically. To test this hypothesis we compared the performance of young and older adults on two bimanual circle drawing tasks that utilize either low-level emergent timing processes (continuous circle drawing) or higher-level event-based timing mechanisms (intermittent circle drawing). The circle drawing tasks were performed with the hands coupled in either a symmetrical or asymmetrical coordination mode and at two individually-determined movement frequencies (comfortable and fast). Older participants were able to match the performance of young adults under both coordination modes and movement frequencies in the bimanual continuous circling task, but showed significantly greater temporal variability when performing the intermittent circling task. The results of the study are in accordance with the view that age-related effects will be observed in tasks in which movement timing is guided by high-level representations but not in tasks involving relatively automatic low-level timing processes.

Long-Range Correlation in Synchronization and Syncopation Tapping: A Linear Phase Correction Model

We propose in this paper a model for accounting for the increase in long-range correlations observed in asynchrony series in syncopation tapping, as compared with synchronization tapping. Our model is an extension of the linear phase correction model for synchronization tapping. We suppose that the timekeeper represents a fractal source in the system, and that a process of estimation of the half-period of the metronome, obeying a random-walk dynamics, combines with the linear phase correction process. Comparing experimental and simulated series, we show that our model allows accounting for the experimentally observed pattern of serial dependence. This model complete previous modeling solutions proposed for self-paced and synchronization tapping, for a unifying framework of event-based timing.

Coordinating Asynchronous and Open Distributed Systems under Semiring-Based Timing Constraints

For asynchronous and open distributed systems, dynamicity, openness, and stringent quality of service requirements pose great challenges to model and develop such systems. The Actor-Role-Coordinator (ARC) model was previously proposed to address these challenges. The role concept in the model addresses the dynamicity and openness issues by providing abstractions of actor behaviors. In this paper, we focus on coordinating actors and roles through message manipulations based on event-based timing constraints. In addition, different types of timing constraints are generalized into a semiring-based constraint structure; and the all-pairs extremal paths algorithm on closed semirings is applied to derive the most stringent constraints which are logical implications of the original set of constraints. The derived implicit constraints are further used to test constraint inclusions and decide intersections between feasible regions of timing constraint sets. The integration of the ARC model and the semiring-based timing constraint models is prototyped using Maude, a rewriting logic language. We further use the proposed approach to solve the Restaurant for Dining Philosophers problem and illustrate the expressiveness of the ARC and the semiring-based timing constraint models for exogenous and composable coordination of open systems.

Fractal models for event-based and dynamical timers

Some recent papers proposed to distinguish between event-based and emergent timing. Event-based timing is conceived as prescribed by events produced by a central clock, and seems to be used in discrete tasks (e.g., finger tapping). Emergent or dynamical timing refers to the exploitation of the dynamical properties of effectors, and is typically used in continuous tasks (e.g., circle drawing). The analysis of period series suggested that both timing control processes possess fractal properties, characterized by self-similarity and long-range dependence. The aim of this article is to present two models that produce period series presenting the statistical properties previously evidenced in discrete and continuous rhythmic tasks. The first one is an adaptation of the classical activation/threshold models, including a plateau-like evolution of the threshold over time. The second one is a hybrid limit-cycle model, including a time-dependent linear stiffness parameter. Both models reproduced satisfactorily the spectral signatures of event-based and dynamical timing processes, respectively. The models also produced auto-correlation functions similar to those experimentally observed. Using ARFIMA modeling we show that these simulated series possess fractal properties. We suggest in conclusion some possible extensions of this modeling approach, to account for the effects of metronomic pacing, or to analyze bimanual coordination.

Impaired rhythm generation in essential tremor

It has been suggested that the cerebellum plays a role in the event-based timing of synchronized repetitive movements. We hypothesized that regularity of rhythmic movements in essential tremor (ET) is impaired, since several lines of evidence suggest the involvement of the cerebellum in the pathomechanism of ET. To test this assumption, we examined the regularity and the maximum frequency of auditory paced repetitive movements at slow and fast stimulus rate in 34 ET patients. Variability of rhythmic finger tapping and alternating hand movements, defined by the standard deviation of movement offset before or after the pacing signal, was significantly higher compared to healthy controls. Timing of rhythmic movements of the two hands was disturbed to the same degree. Our results suggest a severe deficit of event-based rhythm generation on both sides in ET, supporting the presumed bilateral cerebellar dysfunction in this disorder.

Comparison of patients with Parkinson’s disease or cerebellar lesions in the production of periodic movements involving event-based or emergent timing

We have hypothesized a distinction between the processes required to control the timing of different classes of periodic movements. In one class, salient events mark successive cycles. For these movements, we hypothesize that the temporal goal is a requisite component of the task representation, what we refer to as event-based timing. In the other class, the successive cycles are produced continuously. For these movements, alternative control strategies can optimize performance, allowing timing to be emergent. In a previous study, patients with cerebellar lesions were found to be selectively impaired on event-based timing tasks; they were unimpaired on a continuously produced task. In the present study, patients with Parkinson’s disease were tested on repetitive movement tasks in which timing was either event-based or emergent. Temporal variability on either type of task did not differ between on- and off-medication sessions for the Parkinson’s patients nor did patient performance differ from that of controls. These results suggest that the basal ganglia play a minimal role in movement timing and that impairments on event-based timing tasks are specific to cerebellar damage.