Synchrony Conditions Research Articles

Silent disco: dancing in synchrony leads to elevated pain thresholds and social closeness

Moving in synchrony leads to cooperative behavior and feelings of social closeness, and dance (involving synchronization to others and music) may cause social bonding, possibly as a consequence of released endorphins. This study uses an experimental paradigm to determine which aspects of synchrony in dance are associated with changes in pain threshold (a proxy for endorphin release) and social bonding between strangers. Those who danced in synchrony experienced elevated pain thresholds, whereas those in the partial and asynchrony conditions experienced no analgesic effects. Similarly, those in the synchrony condition reported being more socially bonded, although they did not perform more cooperatively in an economic game. This experiment suggests that dance encourages social bonding among co-actors by stimulating the production of endorphins, but may not make people more altruistic. We conclude that dance may have been an important human behavior evolved to encourage social closeness between strangers.

Differential contribution of demographic rate synchrony to population synchrony in barn swallows

Populations of many species show temporally synchronous dynamics over some range, mostly caused by spatial autocorrelation of the environment that affects demographic rates. Synchronous fluctuation of a demographic rate is a necessary, but not sufficient condition for population synchrony because population growth is differentially sensitive to variation in demographic rates. Little is known about the relative effects of demographic rates to population synchrony, because it is rare that all demographic rates from several populations are known. We develop a hierarchical integrated population model with which all relevant demographic rates from all study populations can be estimated and apply it to demographic data of barn swallows Hirundo rustica from nine sites that were between 19 and 224 km apart from each other. We decompose the variation of the population growth and of the demographic rates (apparent survival, components of productivity, immigration) into global and local temporal components using random effects which allowed the estimation of synchrony of these rates. The barn swallow populations fluctuated synchronously, but less so than most demographic rates. The highest synchrony showed the probability of double brooding, while fledging success was highly asynchronous. Apparent survival, immigration and total productivity achieved intermediate levels of synchrony. The growth of all populations was most sensitive to changes in immigration and adult apparent survival, and both of them contributed to the observed temporal variation of population growth rates. Using a simulation model, we show that immigration and apparent survival of juveniles and adults were able to induce population synchrony, but not components of local productivity due to their low population growth rate sensitivity. Immigrants are mostly first-time breeders, and consequently, their number depends on the productivity of neighbouring populations. Since total productivity was synchronized, we conclude that it contributed to population synchrony in an indirect way through dispersing individuals which appear as immigrants at the local scale. The hierarchical integrated population model is promising for achieving an improved mechanistic understanding of population synchrony.

Audiovisual integration directing attention to the temporal dynamics of biological motion

People are adept at recognizing biological motion portrayed by a handful of dots (Johansson, 1973). Visual processing of biological motion is influenced by accompanying information from different sensory modalities (Arrighi et al., 2009; Saygin et al., 2008; Thomas & Shiffrar, 2010) or neighboring biological motion (Ikeda et al., 2013; Thornton et al., 2004). In this study, we investigated the interaction between the two by manipulating 1) the temporal synchrony between visual and auditory information of the biological walkers and 2) the congruency of gait direction between target and flanker walkers. Participants performed a 2-AFC gait direction discrimination (right vs left) of a central target walker flanked by two peripheral point-light figures walking out-of-phase relative to the central figure. There were four audio-visual synchrony conditions: three conditions in which an electronic beep onset was synchronous with either the footsteps of the target (target match), the flankers (flanker match), or between those two (mismatch); and a condition with no sound. To ensure sufficient exposure to the audio-visual synchrony, the flankers and sound were presented for two gait cycles prior to the onset of the central target, which had a gait direction either congruent or incongruent with the flankers. We found statistically significant main effects of sound and congruency on RT. Specifically, participants were slower to report the target gait direction when the timing of the auditory cue matched or was slightly offset (mismatched) from the steps of the task-irrelevant flankers, and RTs were slower on trials with incongruent target and flanker gait direction. Pairwise comparisons revealed significant effects of congruency only when the audio timing matched the target gait or was not presented, but not in the other two conditions. These results suggest bimodal temporal integration directs attention to temporal dynamics of biological motion, mitigating the interference of spatially proximal neighboring motion. Meeting abstract presented at VSS 2015. Language: en

Analytical condition for synchrony in a neural network with two periodic inputs

In this study, we apply a mean-field theory to the neural network model with two periodic inputs in order to clarify the conditions of synchronies. This mean-field theory yields a self-consistent condition for the synchrony and enables us to study the effects of synaptic connections for the behavior of neural networks. Then, we obtain a condition of synaptic connections for the synchrony with the cycle time T. The neurons in neural networks receive sensory inputs and top-down inputs from outside of the network. When the network neurons receive two or more inputs, their synchronization depends on the conditions of inputs. We also analyze this case using the mean-field theory. As a result, we clarify the following points: (i) The stronger synaptic connections enhance the shorter synchrony cycle of neurons. (ii) The cycle of the synchrony becomes longer as the cycle of external inputs becomes longer. (iii) The relationships among synaptic weights, the properties of input trains, and the cycle of synchrony are expressed by one equation, and there are two areas for asynchrony. With regard to the third point, the yielded equation is so simple for calculation that it can easily provide us with feasible and infeasible conditions for synchrony.

Coding of multisensory temporal patterns in human superior temporal sulcus

Philosophers, psychologists, and neuroscientists have long been interested in how the temporal aspects of perception are represented in the brain. In the present study, we investigated the neural basis of the temporal perception of synchrony/asynchrony for audiovisual speech stimuli using functional magnetic resonance imaging (fMRI). Subjects judged the temporal relation of (a)synchronous audiovisual speech streams, and indicated any changes in their perception of the stimuli over time. Differential hemodynamic responses for synchronous versus asynchronous stimuli were observed in the multisensory superior temporal sulcus complex (mSTS-c) and prefrontal cortex. Within mSTS-c we found adjacent regions expressing an enhanced BOLD-response to the different physical (a)synchrony conditions. These regions were further modulated by the subjects' perceptual state. By calculating the distances between the modulated regions within mSTS-c in single-subjects we demonstrate that the “auditory leading (AL)” and “visual leading (VL) areas” lie closer to “synchrony areas” than to each other. Moreover, analysis of interregional connectivity indicates a stronger functional connection between multisensory prefrontal cortex and mSTS-c during the perception of asynchrony. Taken together, these results therefore suggest the presence of distinct sub-regions within the human STS-c for the maintenance of temporal relations for audiovisual speech stimuli plus differential functional connectivity with prefrontal regions. The respective local activity in mSTS-c is dependent both upon the physical properties of the stimuli presented and upon the subjects' perception of (a)synchrony.

Intervention targeting development of socially synchronous engagement in toddlers with autism spectrum disorder: a randomized controlled trial

Social and communication impairments are core deficits and prognostic indicators of autism. We evaluated the impact of supplementing a comprehensive intervention with a curriculum targeting socially synchronous behavior on social outcomes of toddlers with autism spectrum disorders (ASD). Fifty toddlers with ASD, ages 21 to 33 months, were randomized to one of two six-month interventions: Interpersonal Synchrony or Non-Interpersonal Synchrony. The interventions provided identical intensity (10 hours per week in classroom), student-to-teacher ratio, schedule, home-based parent training (1.5 hours per month), parent education (38 hours), and instructional strategies, except the Interpersonal Synchrony condition provided a supplementary curriculum targeting socially engaged imitation, joint attention, and affect sharing; measures of these were primary outcomes. Assessments were conducted pre-intervention, immediately post-intervention, and, to assess maintenance, at six-month follow-up. Random effects models were used to examine differences between groups over time. Secondary analyses examined gains in expressive language and nonverbal cognition, and time effects during the intervention and follow-up periods. A significant treatment effect was found for socially engaged imitation (p = .02), with more than doubling (17% to 42%) of imitated acts paired with eye contact in the Interpersonal Synchrony group after the intervention. This skill was generalized to unfamiliar contexts and maintained through follow-up. Similar gains were observed for initiation of joint attention and shared positive affect, but between-group differences did not reach statistical significance. A significant time effect was found for all outcomes (p < .001); greatest change occurred during the intervention period, particularly in the Interpersonal Synchrony group. This is the first ASD randomized trial involving toddlers to identify an active ingredient for enhancing socially engaged imitation. Adding social engagement targets to intervention improves short-term outcome at no additional cost to the intervention. The social, language, and cognitive gains in our participants provide evidence for plasticity of these developmental systems in toddlers with ASD. http://www.clinicaltrials.gov/ct2/show/NCT00106210?term = landa&rank = 3.

The Asynchronous Bounded-Cycle model

This paper shows how synchrony conditions can be added to the purely asynchronous model in a way that avoids any reference to message delays and computing step times, as well as system-wide constraints on execution patterns and network topology. Our Asynchronous Bounded-Cycle (ABC) model just bounds the ratio of the number of forward- and backward-oriented messages in certain (“relevant”) cycles in the space–time diagram of an asynchronous execution. We show that clock synchronization and lock-step rounds can be implemented and proved correct in the ABC model, even in the presence of Byzantine failures. Furthermore, we prove that any algorithm working correctly in the partially synchronous Θ-Model also works correctly in the ABC model. In our proof, we first apply a novel method for assigning certain message delays to asynchronous executions, which is based on a variant of Farkas’ theorem of linear inequalities and a non-standard cycle space of graphs. Using methods from point-set topology, we then prove that the existence of this delay assignment implies model indistinguishability for time-free safety and liveness properties. We also introduce several weaker variants of the ABC model, and relate our model to the existing partially synchronous system models, in particular, the classic models of Dwork, Lynch and Stockmayer and the query–response model by Mostefaoui, Mourgaya, and Raynal. Finally, we discuss some aspects of the ABC model’s applicability in real systems, in particular, in the context of VLSI Systems-on-Chip.

Conflicting immune responses can prolong the length of infection in Plasmodium falciparum malaria

We have recently proposed a new model for antigenic variation in Plasmodium falciparum that relies on a network of partially cross-protective immune responses to orchestrate this complex immune evasion process. In addition to exhibiting prolonged oscillations of single variants that resemble the sequential dominance of immunologically distinct antigenic types, the model implies that a higher efficacy of cross-reactive immunity actually increases the length of infection while reducing severity of disease. Here, we analyse the behaviour of a reduced system under conditions of perfect synchrony between variants to demonstrate that these features of this system can be attributed to the antagonism between cross-reactive and variant-specific responses.

A spiking neuron model for synchronous flashing of fireflies

Certain species of fireflies show a group behavior of synchronous flashing. Their synchronized and rhythmic flashing has received much attention among many researchers, and there has been a study of biological models for their entrainment of flashing. The synchronous behavior of fireflies resembles the firing synchrony of integrate-and-fire neurons with excitatory or inhibitory connections. This paper shows an analysis of spiking neurons specialized for a firefly flashing model, and provides simulation results of multiple neurons with various transmission delays and coupling strengths. It also explains flashing patterns of some firefly species and examines the synchrony conditions depending on transmission delays and coupling strengths.

Role of across-muscle motor unit synchrony for the coordination of forces

Evidence from five-digit grasping studies indicates that grip forces exerted by pairs of digits tend to be synchronized. It has been suggested that motor unit synchronization might be a mechanism responsible for constraining the temporal relationships between grip forces. To evaluate this possibility and quantify the effect of motor unit synchrony on force relationships, we used a motor unit model to simulate force produced by two muscles using three physiological levels of motor unit synchrony across the two muscles. In one condition, motor units in the two muscles discharged independently of one another. In the other two conditions, the timing of randomly selected motor unit discharges in one muscle was adjusted to impose low or high levels of synchrony with motor units in the other muscle. Fast Fourier transform analysis was performed to compute the phase differences between forces from 0.5 to 17 Hz. We used circular statistics to assess whether the phase differences at each frequency were randomly or non-randomly distributed (Rayleigh test). The mean phase difference was then computed on the non-random distributions. We found that the number of significant phase-difference distributions increased markedly with increasing synchronization strength from 18% for no synchrony to 65% and 82% for modest and strong synchrony conditions, respectively. Importantly, most of the mean angles clustered at very small phase difference values (approximately 0 to 10 degrees), indicating a strong tendency for forces to be exerted in a synchronous fashion. These results suggest that motor unit synchronization could play a significant functional role in the coordination of grip forces.

Functional connectivity between the red nucleus and the hippocampus supports the role of hippocampal formation in sensorimotor integration.

Experiments were carried out in urethane-anesthetized rats to evaluate the hypothesis that the red nucleus has functional connections with the hippocampal formation. Depth profiles of electrical stimulation in experiment 1 confirmed that stimulation administered to the red nucleus elicited theta field activity in the hippocampal formation with a linear relationship between stimulus intensity and theta frequency. Experiment 2 showed that microinfusion of local anesthetic procaine hydrochloride into the medial septum resulted in a reversible blockade of theta field activity elicited by electrical stimulation of the red nucleus. In experiment 3, the discharge activity of red nucleus cells was recorded during the field conditions of hippocampal synchrony (theta) and hippocampal asynchrony [large amplitude irregular activity (LIA)]. Analysis revealed that 26/46 (56%) of red nucleus cells were theta-related, whereas the remaining 20 (44%) were nonrelated. The majority of theta-related cells were classified as tonic theta-on. A brief increase above the basal discharge rate of tonic theta-on red nucleus cells during LIA predicted the transition from LIA to theta with 400- to 500-ms latency. Furthermore, higher frequency transitional discharges predicted higher theta frequencies, whereas higher discharge rates during theta predicted shifts to higher theta frequencies. The results supported the conclusion that the red nucleus, traditionally associated with motor functions, is functionally connected with the neural circuitry involved in the generation of theta band oscillation and synchrony in the hippocampal formation, in agreement with the predictions of the sensorimotor integration model of hippocampal function.

Infants’ learning, memory, and generalization of learning for bimodal events

Study 1 investigated whether infants 3 and 7 months of age show differential learning of and memory for sight–sound pairs depending on whether or not temporal synchrony was present; memory was assessed after a 10-min and 1-week interval. Study 2 examined whether 7-month-olds show generalization of learning when they encounter novel bimodal events that are similar (changes in size, orientation, or color, and spectral sound properties) to the sight–sound pairs learned 1 week earlier based on temporal synchrony. For Study 1, infants received a familiarization phase followed by a paired-comparison preference procedure to assess for learning of the sight–sound pairs. One week later a memory test was given. Results confirmed that 7-month-olds had no difficulty learning auditory–visual pairings regardless of whether or not events were temporally synchronous, and they remembered these 10 min and 1 week later. In contrast, 3-month-olds showed poorer learning of sight–sound associations in the no-synchrony than synchrony conditions, and memory for sight–sound pairs 1 week later was shown only for the synchrony conditions. Results for Study 2 revealed generalization of learning of bimodal pairings under all stimulus conditions after a 1-week interval at 7 months of age. Implications of these findings for development of intersensory knowledge are discussed.

Development of single mouse blastomeres enlarged to zygote size in conditions of nucleo-cytoplasmic synchrony.

The following blastomeres were enlarged to the size of the zygote by one, two or three rounds of blastomere enucleation and electrofusion: (1) from the 2-cell stage (referred to as 2/1 embryos), (2) from the 4-cell stage (referred to as 4/1 embryos), (3) from the 8-cell stage (referred to as 8/1 embryos). Such single enlarged blastomeres developed into blastocysts in vivo in 55.5% (2/1), 28% (4/1) and 6.6% (8/1) of cases. Their mean cell numbers were 45.3, 24.5 and 13.0 in 2/1, 4/1 and 8/1 embryos, respectively. When a blastomere nucleus from another mouse strain (heterologous nucleus) was substituted for a blastomere's own (homologous) one, then fewer blastocysts were formed from 2/1 embryos (34.6%), but not from 4/1 and 8/1 embryos. Five young (10.4%) were born from 2/1 embryos with a homologous nucleus, and nine (8.3%) from 2/1 embryos with heterologous nuclei. Four young (7.1%) were born from 4/1 embryos with heterologous nuclei. No young were obtained from 8/1 embryos. Incorrect cavitation resulting in trophoblastic vesicles and false blastocyst formation was common in 4/1 embryos (18.7% of those with homologous nuclei and 41.3% with heterologous nuclei) and in 8/1 embryos (53.3% and 43.7%, respectively). The results show that neither enlargement to zygote size nor nucleo-cytoplasmic synchrony improve postimplantation development of 4- and 8-cell stage blastomeres when compared with less enlarged non-synchronous ones; therefore, it appears that an insufficient number of inner cell mass cells in blastocysts and not too small a size of isolated blastomeres precludes their postimplantation development.

Plasma natriuretic peptide levels and daily physical activity in patients with pacemaker implantation.

To determine whether plasma ANP and/or BNP levels can be used to detect limitations in daily physical activity after pacemaker implantation, we measured plasma ANP and BNP levels at a pacemaker follow-up clinic in 56 patients (62+/-15 yrs, 2AAI, 9VVI, 34DDD, 7VDD and 4 rate-responsive modes), daily physical activity evaluated by a specific activity scale questionnaire (METs) and VO2 max obtained by expired gas analysis during ergometer exercise. A very close correlation (n=6, r=0.89, p<0.05) was obseved between. ANP in patients with daily physical activity class III (2-4 METs, n=21) was significantly higher than class II (5-6 METs, n=23, p<0.01) and class I (>7 METs, n=8, p<0.01), while BNP in class III patients was significantly higher than in class II (p<0.0001) and class I (p<0.0001) patients. Significant correlations between daily physical activity and BNP (r=-0.64, p<0.0001) and ANP (r=-0.43, p<0.001) were observed. Physiological pacing mode did not necessarily offer a better profile for BNP levels compared with non-physiological pacing modes. Patients with ventricular pacing (wide QRS: VDD, RR-VVI and VVI) showed significantly high ANP (p<0.01) and BNP (p<0.01) levels compared with those in patients with atrial pacing (narrow QRS: AAI and RR-AAI). During exercise, plasma catecholamines and ANP levels were significantly elevated, however, BNP levels, which were already elevated at rest, did not change significantly, and reflected a limitation of daily physical activity. The present study revealed that 37.5% of the patients displayed an elevation in BNP and this was judged to be a limitation of physical activity class III being equivalent to NYHA II or more. Elevated resting BNP levels reflected a limitation in daily physical activity in these patients. These findings suggested a third condition for physiological pacing--synchronization of ventricular contraction (narrow QRS pacing)--in addition to the two conventional conditions of atrioventricular synchrony and rate-responsiveness.

Motor-unit synchronization increases EMG amplitude and decreases force steadiness of simulated contractions.

The purpose of the study was to determine the effect of motor-unit synchronization on the surface electromyogram (EMG) and isometric force using a computer model of muscle contraction. The EMG and force were simulated by generating muscle fiber action potentials, defining motor-unit mechanical characteristics and territories, estimating motor-unit action potentials, specifying motor-unit discharge times, and imposing various levels of motor-unit synchronization. The output (EMG and force) was simulated at 11 levels of excitation, ranging from 5 to 100% of maximum. To synchronize motor-unit activity, selected motor-unit discharge times were adjusted; however, the number of motor units recruited and the average discharge rate of each unit was constant across synchronization conditions for a given level of excitation. Two levels of synchronization were imposed on the discharge times: a moderate and a high level, which approximated the experimentally observed range of motor-unit synchronization. The moderate level of synchrony caused the average EMG to increase by approximately 65%, whereas the high level caused a 130% increase in the EMG with respect to the no-synchrony condition. Neither synchrony condition influenced the magnitude of the average force. However, motor-unit synchronization did increase the amplitude of the fluctuations in the simulated force, especially at intermediate levels of excitation. In conclusion, motor-unit synchronization increased the amplitude of the average rectified EMG and decreased the steadiness of the force exerted by the muscle in simulated contractions.

The effects of witness identity masking on memory and person perception

Abstract Two experiments are reported that investigated the effects of making the identity of a witness using a videotape of a testimony taken from a real court case. In the first experiment the witness for the prosecution was masked using either a grey circle, pixelation or negation. In the second experiment, the soundtrack of the testimony was played whilst a still picture of a courtroom, a static image of the witness's face or an out of synchrony version of the video footage was displayed. In both experiments these manipulations were compared to an unmasked control group. Results showed that mock jurors recall of testimony was significantly impaired in all but the negation and out of synchrony conditions. No effects on witness credibility were observed. It is suggested that identity masking impairs recall by disrupting nonverbal communication cues and further that the technique of masking identity through negation is not susceptible to this disruption.

Changes in the rate of oxygen consumption in synchronous cultures of the fission yeast Schizosaccharomyces Pombe

Oxygen consumption was measured with an oxygen electrode in synchronous cultures of S. pombe. There were changes during the cell cycle in the rate of oxygen uptake, which are most clearly shown as oscillations in acceleration curves (rate of the rate of uptake). Under various conditions of selection and induction synchrony the acceleration curves are similar to those found earlier for CO2 production. As with CO2 production, the oscillations continued after a block to the DNA-division cycle. There were, however, two differences between oxygen uptake and CO2 production. The oxygen oscillations were more marked and also were out of phase by half a cycle. The respiratory coefficient therefore changes through the cycle.

On the minimal synchronism needed for distributed consensus

Reaching agreement is a primitive of distributed computing. Whereas this poses no problem in an ideal, failure-free environment, it imposes certain constraints on the capabilities of an actual system: A system is viable only if it permits the existence of consensus protocols tolerant to some number of failures. Fischer et al. have shown that in a completely asynchronous model, even one failure cannot be tolerated. In this paper their work is extended: Several critical system parameters, including various synchrony conditions, are identified and how varying these affects the number of faults that can be tolerated is examined. The proofs expose general heuristic principles that explain why consensus is possible in certain models but not possible in others.

Studies on synchronized cells: Inhibition of cell division of Astasia longa by 8-azaguanine

Astasia longa growing exponentially at 25 °C respond to the addition of 8-azaguanine by an initial decrease of their growth rate, lasting for about two generations, followed by a further decrease in growth rate. Relatively small concentrations of 8-azaguanine, added at the beginning of a cold period to cells growing under conditions of synchrony cause a failure to divide in the ensuing warm period. The effect of 8-azaguanine in preventing cell division decreases as it is added later in the cold period, and if it is added at the end of the cold period the cells divide in the immediately ensuing warm period but then fail to divide in the next warm period. 8-azaguanine cause no gross changes in the RNA or protein levels of these cells, and is not incorporated in the RNA to any large extent. The inhibitory action of 8-azaguanine is not reversed by guanosine and is only partially reversed by guanine. The nucleotide pool of these cells increases during the cold period. When the cells are exposed to 14C-labeled 8-azaguanine this compound and at least one derivative are found in the nucleotide pool. The effect of 8-azaguanine on exponentially growing cells is reparable. The block of division in synchronized cells is not permanent, since the cells will divide in the presence of 8-azaguanine if they are released from the temperature cycle. Upon release from the cycle, the cells retain the temperature-induced alignment of their cell cycles, indicating that the 8-azaguanine does not interfere with the temperature sensitive timing mechanism responsible for synchrony. 8-azaguanine increases the mitotic time in Astasia and its selective effect on the division of synchronized Astasia is probably a consequence of the interaction between the delay introduced in mitosis and the timing of the temperature cycle. Possible biochemical modes of action of this analogue are discussed.