Shared dynamics of attentional cost and pattern stability

Effect of verbal cues on the coupling and stability of anti-phase bimanual coordination pattern in children with probable developmental coordination disorder

The study of the emergence and stability of bimanual and interlimb coordination patterns in children with Developmental Coordination Disorder (DCD) has shown that they encounter greater difficulties in coupling their limbs compared to typically developing (TD) children. Verbal cues have been identified as strategies to direct children's attention to more relevant task information, thus potentially improving motor performance. Consequently, this study investigated the effect of providing verbal cues on the execution of bimanual tasks in children with and without probable DCD. Twenty-eight children aged 9-10, matched by age and gender, were divided into two groups: pDCD [n = 14] and TD. The children performed bilateral trajectory movements with both hands (horizontal back-and-forth), holding a pen on a tablet, in anti-phase (180°) coordination pattern, in two conditions: No cues and Verbal cues. In the last condition, children received verbal cues to maintain the anti-phase pattern even with an increase in hand oscillation frequency. Relative phase and variability of relative phase between the hands were calculated for analysis of pattern coupling and stability. Hand cycles, movement amplitude, and tablet pressure force were calculated to analyze pattern control parameters. All these variables were compared between groups and conditions. The results indicated that despite the pDCD group showing greater variability in the anti-phase coordination pattern compared to the TD group, both groups performed better in the Verbal cues than the No cues condition. Furthermore, the pDCD group exhibited more hand movement cycles and applied greater pressure force compared to the TD group, suggesting different motor control strategies during the bimanual task. It is suggested that the use of verbal cues during bimanual task execution improves children's performance, potentially by promoting interaction between attention, as a cognitive function, and intrinsic coordination dynamics, thereby reducing variability in the perceptual-motor system.

Energetic and Cognitive Demands of Treading Water: Effects of Technique and Expertise

Being able to tread water effectively can improve the likelihood of survival following accidental immersion. People tread water in various ways, ranging from rudimentary 'doggy-paddle' to more elaborate techniques like the eggbeater, but little is known about the energetic and cognitive requirements of treading water. We therefore aimed to measure the demands of treading water techniques for people of different experience levels. Three cohorts, comprising 21 adult water treading experts (water polo players), 15 intermediate swimmers and 16 inexperienced swimmers, treaded water for 3 min each using four different techniques while cognitive and energetic economy measures were taken. For inexperienced swimmers, the flutter kick and breaststroke patterns produced the lowest self-reported physical and task load (rating of perceived exertion, NASA task load index), while cognitive (probe reaction time), cardiac (heart rate) and metabolic (oxygen consumption) load did not differ between techniques. In contrast, for expert water treaders, both breaststroke and eggbeater patterns produced lower cognitive, cardiac and metabolic loads. For intermediate swimmers, breaststroke resulted in the lowest cardiac and metabolic loads, as well as self-reported task load. Probe reaction time was highest while performing the eggbeater technique, indicating that this technique was challenging to coordinate and cognitively demanding. While the energetic demands of antiphase kicking patterns (such as eggbeater in experts or flutter kick in beginners) may be similarly low, the symmetric coordination of upright breaststroke may explain why this pattern's cognitive economy was favourable for all groups. As the eggbeater can be challenging to perform for many people, an upright breaststroke technique is an adequate alternative to adopt in survival situations.

Rhythmic interlimb coordination of the lower limbs in multiple sclerosis during auditory pacing to three different frequencies

BACKGROUND

Multiple sclerosis (MS) is a demyelinating disorder of the central nervous system with heterogeneous symptoms. Persons with MS (PwMS) show reduced walking capacity with changes in their gait pattern. It is unknown to which extent coordination deficits are present in PwMS, which can be measured by seated lower leg interlimb coordination tasks, and to which extent they are related to motor and cognitive function.

RESEARCH QUESTION

How is the control of interlimb coordination of the lower limbs characterized in PwMS compared to healthy controls (HC) during a seated rhythmical coordination task and what is the relationship between interlimb coordination, motor or cognitive function?

METHODS

Rhythmical interlimb coordination was assessed during a single session in 38 PwMS and 13 HC, using a seated rhythmical coordination task, comprising of antiphase flexion-extension of the lower limbs, to metronomes at 0.75 Hz, 1.00 Hz, 1.50 Hz. Outcomes were phase coordination index (PCI), movement amplitude and movement frequency. Correlations between interlimb coordination, motor, and cognitive function were examined.

RESULTS

PwMS showed impaired walking capacity but preserved cognitive function. Mixed model analysis revealed a significant effect of group and metronome frequency for PCI, attenuated by the variability in generating knee (antiphase flexion-extension) movements. Movement amplitude was highest at metronome frequency 1.00 Hz. In PwMS significant correlations were found between PCI and cognitive function when performing the task at metronome frequencies 0.75 Hz and 1.50 Hz, as well as motor function at 1.50 Hz.

SIGNIFICANCE

PwMS had a higher variability in interlimb coordination compared to HC. The most stable interlimb antiphase coordination mode was performed at 1.00 Hz. Significant correlations support the existence of a relationship between information processing speed, as well as walking impairment, with interlimb coordination. While cognitive and motor control are always needed for interlimb coordination movements, associations are strongest in the deviant higher and lower metronome rhythms.

Use of fNIRS to Characterize the Neural Mechanism of Inter-Individual Rhythmic Movement Coordination

Background: Inter-individual rhythmic movement coordination plays an important role in daily life, particularly in competitive sports. Behaviorally, it is more challenging to coordinate alternating movements than symmetrical movements. The neural activity underlying these different movement coordination modes remains to be clarified, particularly considering complex inter-individual coordination differences.

Methods: To further test the neural basis of inter-individual rhythmic movement coordination, a revised experimental paradigm of inter-individual coordination was adopted. Participants were asked to perform symmetric, alternate, or single movements (swinging the lower part of the leg) in the same rhythm. A multi-channel, continuous wave, functional near-infrared spectral (fNIRS) imaging instrument was used to monitor hemodynamic activity while 40 volunteers (9 male pairs and 11 female pairs) performed the task. Multivariate analyses of variance were conducted to compare mean oxy-hemoglobin concentration ([HbO]) across experimental conditions.

Results: A significant three-way interaction (leg-swing condition × ROI × laterality) on mean [HbO] was observed. Post hoc analysis revealed a significant main effect of leg-swing condition only in brain regions of interest [right inferior parietal lobule (IPL)] contralateral to movement execution. Activation in brain regions of interest [right inferior parietal lobule (IPL)] was much stronger in alternate mode compared with symmetric or single modes, and the differences between symmetric and single mode were not statistically significant. This result suggests that the alternate mode of movement coordination was more likely to be supported by the IPL region than the other modes.

Conclusion: The present findings provide neural evidence relevant to the theory of self-organization of movement coordination, in which an alternating movement mode appeared to be a more demanding condition than symmetrical movement.

Expert monitoring and verbal feedback as sources of performance pressure

The influence of monitoring-pressure and verbal feedback on the performance of the intrinsically stable bimanual coordination patterns of in-phase and anti-phase was examined. The two bimanual patterns were produced under three conditions: 1) no-monitoring, 2) monitoring-pressure (viewed by experts), and 3) monitoring-pressure (viewed by experts) combined with verbal feedback emphasizing poor performance. The bimanual patterns were produced at self-paced movement frequencies. Anti-phase coordination was always less stable than in-phase coordination across all three conditions. When performed under conditions 2 and 3, both bimanual patterns were performed with less variability in relative phase across a wide range of self-paced movement frequencies compared to the no-monitoring condition. Thus, monitoring-pressure resulted in performance stabilization rather than degradation and the presence of verbal feedback had no impact on the influence of monitoring pressure. The current findings are inconsistent with the predictions of explicit monitoring theory; however, the findings are consistent with studies that have revealed increased stability for the system's intrinsic dynamics as a result of attentional focus and intentional control. The results are discussed within the contexts of the dynamic pattern theory of coordination, explicit monitoring theory, and action-focused theories as explanations for choking under pressure.

Individual and dyadic rope turning as a window into social coordination

The spontaneous and intentional movement coordination between peoples is well understood. Less is known about such interactions when the coordination is subordinate to the task and when the task involves, next to vision, mechanically induced haptic and kinesthetic coupling between dyadic partners. We therefore investigated dyadic jump rope turning. Fifteen dyadic pairs conjointly turned a jump rope to which five markers were equidistantly attached, and whose movements were recorded in 3D. In addition, each participant turned one side of the rope while the other side was quasi-fixed in an individual baseline condition. The participants' goal was to turn the rope regularly and smoothly. Individual spontaneous turning frequencies differed substantially across participants. Yet, dyadic pairs spontaneously turned the rope at a common frequency, indicative of frequency entrainment. The dyadic rope rotations were less variable despite weaker between near-hand marker coordination than the individual rope rotations, and the degree of performance improvement was most pronounced for participants who were paired with a partner who performed better in the individual condition. The direction and relative strength of the coupling between partners varied substantially across dyads, but the degree of coupling asymmetry had no substantial effect on the rope tuning quality. The absolute degree in which dyadic partners adjusted to each other, however, scaled moderately with their turning performance. Although the individual performances did not predict the dyadic performances, the difference in individual performance between dyadic partners had some predictive value for the dyadic performance. In combination, these results indicate that the partners were functionally adapting to each other in order to satisfy the task goal and suggest that the relative performance differences rather than the individual performances has predictive value for conjoint action.

Performing Isometric Force Control in Combination with a Cognitive Task: A Multidimensional Assessment

Introduction

We used a multidimensional approach to study isometric force control in single and dual-task conditions.

Methods

Multiple measures of performance, efficiency, variability, and structural interference were calculated at low and higher force levels under single (force maintenance) and dual-task (force maintenance and reaction time) conditions.

Results

Reaction time and signal-to-noise ratio were larger in the dual-task conditions. They were also greater for the higher force condition, while sample entropy was lower. Perturbation analyses revealed smaller relative amplitude of downward perturbations for the higher force level.

Discussion

Attentional effort and efficiency are positively related when force level increases, and inversely related to entropy. These relations were presumably mediated by attentional investment. Behavioral perturbations show that attentional resources and structural interference models are not mutually exclusive to account for dual-task situation. Overall, the present study highlights the interest of a multidimensional assessment of force control.

Functional specialization within the supplementary motor area: a fNIRS study of bimanual coordination

Bimanual movements can be performed by flexing and extending the target effectors (e.g., hand muscles) in unison, or by flexing units on one side in unison with extension of the same units on the opposite side. The former movement patterns are generally referred to as in-phase or parallel, whereas the latter patterns are often termed anti-phase movements. It is well known that anti-phase patterns are unstable and tend to spontaneously transition to in-phase movements at higher repetition rates, but the mechanisms and brain regions involved are not fully understood. In the current study, we utilized functional near-infrared spectroscopy (fNIRS) to evaluate whether anterior/posterior subdivisions of the supplementary motor complex (SMA) have distinct functional roles in maintaining in-phase and anti-phase movement patterns. Twelve healthy adult participants completed a bimanual coordination task comprised of anti-phase and in-phase trials as 24-channel fNIRS data was recorded from dorsal-medial motor areas. We examined the relative concentrations of oxygenated and deoxygenated hemoglobin in the channels that were located over the anterior SMA (e.g., pre-SMA) and the SMA proper. Our most interesting results indicated that oxygenated hemoglobin responses were greater in the anterior SMA during performance of anti-phase compared to in-phase movements. In the SMA proper, oxygenated hemoglobin responses did not differ between the two movement patterns. These data suggest that the anterior SMA is critical to programming and maintaining the less stable anti-phase movement patterns, and support the conceptual framework of an anterior-directed gradient of progressively more complex functionality in the SMA.

The role of anticipatory postural adjustments in interlimb coordination of coupled arm movements in the parasagittal plane: III. difference in the energy cost of postural actions during cyclic flexion-extension arm movements, ISO- and ANTI-directionally coupled

When oscillating the upper limbs together in the parasagittal plane, movements coordination is lower (i.e., variability of the interlimb relative phase is higher) in antidirectional (ANTI) than in isodirectional (ISO) coupling. In contrast, we previously observed that for arm movements in the horizontal plane, the coordination was worse in ISO than ANTI and the energetic cost of postural activities was higher in ISO. Having hypothesised that the higher postural cost was one factor responsible for the coordination deficit in horizontal ISO, we measured the oxygen uptake ([Formula: see text]) in parasagittal movements, expecting that in this case too, the postural cost is higher in the less-coordinated mode (ANTI). Breath-by-breath metabolic ([Formula: see text], [Formula: see text]) and cardiorespiratory (HR, [Formula: see text]) parameters were measured in seven participants, who performed cyclic flexions-extensions in the parasagittal plane with either one arm or both arms, in ISO or ANTI coupling and at 1.4, 2.2 and 2.6 Hz. In each condition, the intermittent exercise (12 s movement, 12 s rest) lasted 264 s. A force platform recorded the mechanical actions to the ground. The exercise metabolic cost ([Formula: see text]) was found to be significantly higher in parasagittal ANTI than ISO. The movement amplitude being equal in the two modes, the ANTI-ISO difference should be ascribed to postural activities. This would confirm that the less-coordinated coupling mode requires the higher postural effort in parasagittal movements too. When rising the movement frequency, [Formula: see text] increased and linearly correlated with the coordination loss. Comparison of parasagittal with horizontal movements showed that [Formula: see text] was lower in parasagittal ANTI than in horizontal ISO (the less-coordinated modes), while it was not different between parasagittal ISO and horizontal ANTI (the more-coordinated modes).

Functional neuroimaging of the interference between working memory and the control of periodic ankle movement timing

Background

Limited information processing capacity in the brain necessitates task prioritisation and subsequent adaptive behavioural strategies for the dual-task coordination of locomotion with severe concurrent cognitive loading. Commonly observed strategies include prioritisation of gait at the cost of reduced performance in the cognitive task. Alternatively alterations of gait parameters such as gait velocity have been reported presumably to free processing capacity for the benefit of performance in the cognitive task. The aim of this study was to describe the neuroanatomical correlates of adaptive behavioural strategies in cognitive-motor dual-tasking when the competition for information processing capacity is severe and may exceed individuals’ capacity limitations.

Methods

During an fMRI experiment, 12 young adults performed slow continuous, auditorily paced bilateral anti-phase ankle dorsi-plantarflexion movements as an element of normal gait at .5 Hz in single and dual task modes. The secondary task involved a visual, alphabetic N-back task with presentation rate jittered around .7 Hz. The N-back task, which randomly occurred in 0-back or 2-back form, was modified into a silent counting task to avoid confounding motor responses at the cost of slightly increasing the task′s general coordinative complexity. Participants’ ankle movements were recorded using an optoelectronic motion capture system to derive kinematic parameters representing the stability of the movement timing and synchronization. Participants were instructed to perform both tasks as accurately as possible.

Results

Increased processing complexity in the dual-task 2-back condition led to significant changes in movement parameters such as the average inter-response interval, the coefficient of variation of absolute asynchrony and the standard deviation of peak angular velocity. A regions-of-interest analysis indicated correlations between these parameters and local activations within the left inferior frontal gyrus (IFG) such that lower IFG activations coincided with performance decrements.

Conclusions

Dual-task interference effects show that the production of periodically timed ankle movements, taken as modelling elements of the normal gait cycle, draws on higher-level cognitive resources involved in working memory. The interference effect predominantly concerns the timing accuracy of the ankle movements. Reduced activations within regions of the left IFG, and in some respect also within the superior parietal lobule, were identified as one factor affecting the timing of periodic ankle movements resulting in involuntary ‘hastening’ during severe dual-task working memory load. This ‘hastening’ phenomenon may be an expression of re-automated locomotor control when higher-order cognitive processing capacity can no longer be allocated to the movements due to the demands of the cognitive task. The results of our study also propose the left IFG as a target region to improve performance during dual-task walking by techniques for non-invasive brain stimulation.

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Neural correlates of involuntary ‘hastening’ of movements during cognitive-motor dual-tasking.

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Role of left inferior frontal gyrus and left superior parietal lobe in the temporal regulation of dual-task bilateral movements.

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Dissociation between left-hemisphere parietal involvement in external timing of bilateral movements and right hemisphere parietal involvement in interlimb coordination.

Co-variation between graphic pattern stability and attentional cost: a clue for the difficulty to produce handwritten traces

Attentional cost incurred for generating handwritten graphic patterns was investigated using a classic dual-task procedure, in which a concurrent reaction time (RT) task was used as an index of the attentional cost incurred by the primary graphic task. Eight right-handed adults had to trace graphic patterns, characterized by a 0°, 45°, 90°, 135° or 180° relative phase and corresponding to shapes ranging from lines to ellipses to circles, while responding by a key press as fast as possible to an auditory signal. The results evidenced a strong and significant correlation between the stability of the produced pattern and the associated attentional cost. The amplitude of the minor and major axes of the produced ellipsoids decreased with the increase of movement frequency, as expected by nonlinear models of oscillatory pattern generation. These findings pave the way to the study for the (coordinative) processes for letter (mal)formation in cursive handwriting.

The contribution of postural control and bilateral coordination to the impact of dual tasking on gait

The simultaneous performance of a cognitive task while walking typically alters the gait pattern. In some populations, these alterations have been associated with an increased risk of falls, motivating study of this response from the clinical perspective. The mechanisms responsible for these effects are not fully understood. The concurrent requirement to control upright posture and stepping, a bilaterally coordinated rhythmic task, may be the cause of this so-called dual-tasking effect. To evaluate this possibility, the present study was designed to isolate the individual contribution of these two demands by assessing the effects of cognitive loading on standing (i.e., postural control without bilateral coordination of stepping), cycling (i.e., bilateral coordination similar to stepping, but with minimal postural demands), and walking. We also investigated the effects of aging and parkinsonism on the performance of these three tasks in response to cognitive loading, also referred to as a dual task. Twenty-one healthy young adults, 15 healthy older adults, and 18 patients with Parkinson's disease were assessed while walking, standing, and cycling, with and without an additional cognitive load. In the young adults, the performance on the two motor tasks that involved bilateral coordination deteriorated significantly in response to the dual task, while standing was not impacted. Similar results, although less robust, were observed among the healthy older adults. In contrast, among the patients with Parkinson's disease, the dual-task costs, i.e., the impact of the simultaneously performed cognitive task on the gait pattern, were high in all motor tasks. These findings suggest that walking is especially vulnerable to cognitive loading, in part, because of the unique sensitivity of bilateral coordination of limb movements to the effects of dual tasking.

Covariation of attentional cost and stability provides further evidence for two routes to learning new coordination patterns

This study investigated how learning a new bimanual coordination pattern affects the attentional resources allotted by the CNS to maintain it throughout the acquisition process. The repertoire of the existing stable coordination patterns was individually evaluated before and after practice in order to detect expected changes with learning. Bistable participants, who initially exhibited stable and accurate coordination patterns at 0 degrees and 180 degrees of relative phase, practiced a 90 degrees pattern, whereas multistable participants, who already mastered the 90 degrees pattern, practiced 135 degrees pattern instead. In a typical dual-task paradigm, all participants had to simultaneously perform a reaction time task that assessed the associated attentional cost. Beyond an overall increase in accuracy, the results revealed a significant decrease in the attentional cost for bistable participants, accompanying the stabilization of the 90 degrees pattern with learning, but not for multistable participants, as the 135 degrees pattern barely stabilized. Pattern stability and attentional cost co-evolve during learning and the process follows two different routes depending on the interplay between the task and the learner's coordination abilities before practice.

Limitations on coupling of bimanual movements caused by arm dominance: when the muscle homology principle fails

Studies of bimanual movements typically report interference between motions of the two arms and preference to perform mirror-symmetrical patterns. However, recent studies have demonstrated that the two arms differ in the ability to control interaction torque (INT). This predicts limitations in the capability to perform mirror-symmetrical movements. Here, two experiments were performed to test this prediction. The first experiment included bimanual symmetrical and asymmetrical circle drawing at two frequency levels. Unimanual circle drawing was also recorded. The increases in cycling frequency caused differences between the two arms in movement trajectories in both bimanual modes, although the differences were more pronounced in the asymmetrical compared with the symmetrical mode. Based on torque analysis, the differences were attributed to the nondominant arm's decreased capability to control INT. The intraarm differences during the symmetrical pattern of bimanual movements were similar (although more pronounced) to those during unimanual movements. This finding was verified in the second experiment for symmetrical bimanual oval drawing. Four oval orientations were used to provide variations in INT. Similar to the first experiment, increases in cycling frequency caused spontaneous deviations from perfect bimanual symmetry associated with inefficient INT control in the nondominant arm. This finding supports the limitations in performing mirror-symmetrical bimanual movements due to differences in joint control between the arms. Based on our results and previous research, we argue that bimanual interference occurs during specification of characteristics of required motion, whereas lower-level generation of muscle forces is independent between the arms. A hierarchical model of bimanual control is proposed.

Sentence comprehension affects the dynamics of bimanual coordination: Implications for embodied cognition

Recent work in embodied cognition has demonstrated that language comprehension involves the motor system (e.g., Glenberg & Kaschak, 2002). Such findings are often attributed to mechanisms involving simulations of linguistically described events (Barsalou, 1999; Fischer & Zwaan, 2008). We propose that research paradigms in which simulation is the central focus need to be augmented with paradigms that probe the organization of the motor system during language comprehension. The use of well-studied motor tasks may be appropriate to this endeavour. To this end, we present a study in which participants perform a bimanual rhythmic task (Kugler & Turvey, 1987) while judging the plausibility of sentences. We show that the dynamics of the bimanual task differ when participants judge sentences describing performable actions as opposed to sentences describing events that are not performable. We discuss the general implications of our results for accounts of embodied cognition.

Sensory feedback dependence hypothesis in persons who stutter

The present study investigated the role of sensory feedback (auditory, proprioception, and tactile) at the intra- and inter-gestural levels of speech motor coordination in normal and fast speech rate conditions in two groups: (1) persons who stutter (PWS) and (2) those who do not (PNS). Feedback perturbations were carried out with the use of masking noise (auditory), tendon vibration (proprioception), and nonwords that differed in the amount of required tactile lip contact (/api/+tactile and /awi/-tactile). Comparisons were also made between jaw-free and jaw-immobilized (with a bite-block) task conditions. It was hypothesized that if PWS depend more strongly on sensory feedback control during speech production, they would show an increase in variability of movement coordination in the combined presence of fast speech rates and feedback perturbations, in particular, when jaw motions are blocked and adaptations in the other articulators are required to achieve the task goals. Significant feedback perturbation effects were found for both groups, but the only significant between-group effect was found at fast speech rates in the jaw-free condition, showing that control speakers were more perturbed at the intra-gestural level of coordination than PWS when simultaneous (auditory, proprioceptive, and tactile) perturbations were present. The findings do not provide support for either the feedback dependency or the sensory deficit hypotheses described in the literature to explain movement characteristics found in fluent speech production of PWS.

Factors influencing children's performances of a steady-state bimanual coordination task

Children ages 4, 6, and 8 years and adults performed self-selected, continuous, unimanual and bimanual coordination tasks for 30 s. The length of time performing the task was investigated as a potential control parameter As hypothesized, all groups spent less time in antiphase than in in-phase coordination as the trial continued. These results were interpreted as evidence that the length of time performing a task is a control parameter embedded in any task. The importance of studying control parameters in various developing systems is discussed.

Metabolic and Attentional Energy Costs of Interlimb Coordination

The authors investigated metabolic and attentional energy costs as participants (N = 6) practiced in-phase, antiphase, and 90 degrees -phase cycling (order counterbalanced) on independent bicycle ergometers, with resistance (40 W/ergometer) and frequency (40 rpm) held constant. Coordination stabilized and became more accurate for all 3 cycling modes, as shown by measures of relative phase, but that collective variable could not account for other relevant attributes of the multifaceted motor behavior observed across the 3 coordination modes. In-phase and antiphase cycling were similar in stability and accuracy, but antiphase had the lowest metabolic and attentional energy costs. Because both homologous muscle action and perceptually symmetrical oscillations coincided in the in-phase mode, the absence of predominance of the inphase pattern showed that neither of those musculoskeletal and perceptual factors exclusively determined the strongest attractor of the coordination dynamics. Both metabolic and attentional costs declined with practice, consistent with the hypothesis that adaptive motor behavior is guided by sensory information concerning the energy demands of the task. Attentional cost was influenced not only by the information-processing demands of kinematic stability but also by the metabolic energy demands. Metabolic energy cost appeared to be the crucial determinant of the preferred solution for this coordination task.

Developmental coordination disorder pertains to a deficit in perceptuo-motor synchronization independent of attentional capacities

We investigated from a dynamic pattern perspective to motor coordination whether the deficiency in motor coordination characterizing Developmental Coordination Disorder children pertains to a general disorder in synchronization leading to a lower stability of the performed coordination pattern, and the extent to which the trouble is linked to attentional capacities. Twenty-four DCD children without ADHD aged eight to thirteen and 60 control children were asked (1) to perform a Continuous Performance Test assessing sustained attention; (2) to flex one finger either in synchrony or in syncopation with a visual periodic signal whose frequency was increased stepwise, assessing synchronization abilities. For the attentional task, percentage of exact responses, number of errors and reaction time were recorded. For the synchronization task, we measured relative phase (i.e., the ratio between the stimulus and the response onset and the time separating two successive stimuli). DCD children were significantly more variable than controls in both conditions and the difficulty in synchronization was unrelated to attentional disorders (ANCOVA). These findings support the idea of a general synchronization disorder in DCD children underlying their poor motor coordination. Moreover, this synchronization disorder does not appear to be strictly dependent on the level of sustained attentional capacities.

Age and task-related differences in timing stability, consistency, and natural frequency of children's rhythmic, motor coordination

How does task complexity affect performance in a rhythmic movement task across childhood and into adulthood? The purpose of this experiment was to compare the frequency, stability, and consistency of clapping and walking when these tasks were produced individually and simultaneously by children of different ages. Statistically significant differences were found in natural frequency, stability, and consistency between tasks, limb actions, and among age groups. The results indicated that action-dependent, age-related differences existed. Further, task-related differences existed in these measures that were constant across age groups. This suggested that the role of task was as important as changing morphologies in determining action characteristics across childhood.

Developmental Differences in the Use of Visual Information During a Continuous Bimanual Coordination Task

The authors examined the influence of different amounts of visual information when children 4 (CH4), 6 (CH6), and 8 (CH8) years of age, and adults (n = 12 in each group) performed a steady-state bimanual circle-drawing coordination task at self-selected speeds. All participants maintained in-phase coordination, but different strategies for maintaining the pattern emerged. A predictable relationship between variability and age was not observed, in that the CH8 group was not necessarily more consistent than the CH6 and CH4 groups. The authors conclude that children are transitioning from dependence on kinesthetic feedback to reliance on visual feedback around age 8, as suggested by L. Hay, C. Bard, M. Fleury, and N. Teasdale (1991; L. Hay, M. Fleury, C. Bard, & N. Teasdale, 1994; L. Hay & C. Redon, 1997), and that future studies are needed to further explore visual and kinesthetic feedback as potential control parameters during coordination tasks in developing children.

Learning to Minimize Energy Costs and Maximize Mechanical Work in a Bimanual Coordination Task

The authors addressed the hypothesis that economy in motor coordination is a learning phenomenon realized by both reduced energy cost for a given workload and more external work at the same prepractice metabolic and attentional energy expenditure. "Self-optimization" of movement parameters has been proposed to reflect learned motor adaptations that minimize energy costs. Twelve men aged 22.3 -/+ 3.9 years practiced a 90 degrees relative phase, upper limb, independent ergometer cycling task at 60 rpm, followed by a transfer test of unpracticed (45 and 75 rpm) and self-paced cadences. Performance in all conditions was initially unstable, inaccurate, and relatively high in both metabolic and attentional energy costs. With practice, coordinative stability increased, more work was performed for the same metabolic and attentional costs, and the same work was done at a reduced energy cost. Self-paced cycling was initially below the metabolically optimal, but following practice at 60 rpm was closer to optimal cadence. Given the many behavioral options of the motor system in meeting a variety of everyday movement task goals, optimal metabolic and attentional energy criteria may provide a solution to the problem of selecting the most adaptive coordination and control parameters.

Encoding and retrieval during bimanual rhythmic coordination

In 2 experiments, bimanual 1:1 rhythmic coordination was performed concurrently with encoding or retrieval of word lists. Effects of divided attention (DA) on coordination were indexed by changes in mean relative phase and recurrence measures of shared activity between the 2 limbs. Effects of DA on memory were indexed by deficits in recall relative to baseline. For DA at both encoding and retrieval, the equilibrium values of relative phase were shifted and the degree of shared activity between left and right rhythmic motions was reduced. Recall was reduced, however, only for DA at encoding. The results corroborate and extend those obtained with more conventional secondary tasks (e.g., visual reaction time), suggesting attention dissimilarities between episodic encoding and retrieval.

The relationship between initial errorless learning conditions and subsequent performance

This experiment explores a suggestion by [Maxwell, J.P., Masters, R.S.W., Kerr, E., Weedon, E. (2001). The implicit benefit of learning without errors. Quarterly Journal of Experimental Psychology A 54, 1049-1068] that an initial bout of implicit motor learning confers beneficial performance characteristics, such as robustness under secondary task loading, despite subsequent explicit learning. Participants acquired a complex motor skill (golf putting) over 400 trials. The environment was constrained early in learning to minimize performance error. It was predicted that in the absence of explicit instruction, reducing error would prevent hypothesis testing strategies and the concomitant accrual of declarative (explicit) knowledge, thereby reducing dependence on working memory resources. The effect of an additional cognitive task on putting performance was used to assess reliance on working memory. Putting performance of participants in the Implicit-Explicit condition was unaffected by the additional cognitive load, whereas the performance of Explicit participants deteriorated. The relationship between error correction and episodic verbal reports suggested that the explicit group were involved in more hypothesis testing behaviours than the Implicit-Explicit group early in learning. It was concluded that a constrained, uninstructed, environment early in learning, results in procedurally based motor output unencumbered by disadvantages associated with working memory control.

The metabolic and cognitive energy costs of stabilising a high-energy interlimb coordination task

Kinematic (relative phase error), metabolic (oxygen consumption, heart rate) and attentional (baseline and cycling reaction times) variables were measured while participants practised a high energy-demanding, intrinsically unstable 90 degrees relative phase coordination pattern on independent bicycle ergometers. The variables were found to be strongly inter-correlated, suggesting a link between emerging performance stability with practice and minimal metabolic and attentional cost. The effects of practice of 90 degrees relative phase coordination on the performance of in-phase (0 degrees-phase) and antiphase (180 degrees-phase) coordination were investigated by measuring the relative phase attractor layouts and recording the metabolic and attentional cost of the three coordination patterns before and after practice. The attentional variables did not differ significantly between coordination patterns and did not change with practice. Before practice, the coordination performance was most accurate and stable for in-phase cycling, with antiphase next and 90 degrees-phase the poorest. However, metabolic cost was lower for antiphase than either in-phase or 90 degrees-phase cycling, and the pre-practice attractor layout deviated from that predicted on the basis of dynamic stability as an attractor state, revealing an attraction to antiphase cycling. After practice of 90 degrees-phase cycling, in-phase cycling remained the most accurate and stable, with 90 degrees-phase next and antiphase the poorest, but antiphase retained the lowest metabolic energy cost. The attractor layout had changed, with new attractors formed at the practised 90 degrees-phase pattern and its symmetrical partner of 270 degrees-phase. Considering both the pre- and post-practice results, attractors were formed at either a low metabolic energy cost but less stable (antiphase) pattern or at a more stable but higher metabolic energy cost (90 degrees-phase) pattern, but in neither case at the most stable and accurate (in-phase) pattern. The results suggest that energetic factors affect coordination dynamics and that coordination modes lower in metabolic energy expenditure may compete with dynamically stable modes.

The effects of attention and handedness on coordination dynamics in a bimanual Fitts’ law task

Two experiments were conducted to investigate the effects of attention and handedness on bimanual coordination in the context of a dynamical model of coordinated movements. Participants performed a bimanual, rhythmic Fitts' law task in which the relative amount of attention directed to each task was manipulated by the relative difficulty associated with the pair of targets that each hand tapped. In both experiments, participants tended to lead with their preferred hand. The effects of attention, though, were mixed, which suggested that there was a combined effect of an attentional asymmetry and an asymmetry in the hands' uncoupled frequency, both of which are captured in the dynamical model.

Aging Effects on the Metabolic and Cognitive Energy Cost of Interlimb Coordination

Many everyday motor tasks have high metabolic energy demands, and some require extended practice to learn the required coordination between limbs. Eight older (73.1 +/- 4.4 years) and 8 younger (23.3 +/- 5.9) men practiced a high-energy two-hand coordination task with both 180 degrees and 90 degrees target relative phase. The older group showed greater performance error in both conditions, and performance at 90 degrees was strongly attracted to antiphase coordination (180 degrees). In a retention test one week following the acquisition trials, the older group had learned the 180 degrees condition but did not learn the 90 degrees condition. Metabolic energy cost was not different between groups, but the older men showed higher heart rate and both conditions imposed greater cognitive demands as revealed in auditory probe reaction time. Older adults' motor learning may be inhibited by elevated heart rate at the same oxygen cost, increased cognitive cost, and an attraction toward more established low-energy in-phase or antiphase coordination.

Bimanual Coordination and Musical Experience: The Role of Intrinsic Dynamics and Behavioral Information

Rhythmic interlimb coordination arises from the interaction of intrinsic dynamics and behavioral information, that is, intention, memory, or external information specifying the required coordination pattern. This study investigates the influence of the content of memorized behavioral information on coordination in musically experienced and inexperienced participants. These groups are hypothesized to have different intrinsic dynamics for this task. Stability was assessed in a switching task (variability and switching time). The in-phase, anti-phase, and 90 degrees -phase difference were specified in a neutral and an ecologically relevant manner. Musicians showed more stable coordination than nonmusicians did. No interaction effect was found with memorized behavioral information. Behavioral information showed an interaction effect with phase pattern on coordination variability, with the strongest effect for the 90 degrees -phase pattern. Switching time was affected largely in line with the findings for coordination variability. Participants showed an intraindividual preference for one type of gallop and one type of switch strategy, suggesting different hand roles for the two hands.

Attentional load associated with performing and stabilizing a between-persons coordination of rhythmic limb movements

This study addressed the issue of intentional stabilization of between-persons coordination patterns (in-phase/isodirectional and anti-phase/non-isodirectional) and the attentional cost incurred by the nervous system in maintaining and further stabilizing these coordination patterns. Five pairs of participants performed in-phase and anti-phase interpersonal coordination patterns in dual-task conditions (coordination+RT task). Results showed that: (1) isodirectional pattern (in-phase) was more stable than non-isodirectional pattern (anti-phase), (2) both iso- and non-isodirectional pattern were stabilized intentionally, (3) RT was lower for the isodirectional pattern (i.e., the most stable), and (4) attentional manipulation led to a trade-off between pattern stability and RT performance. These results suggest that performing between-persons coordination patterns incurs a central cost that depends on the coupling strength between the limbs. These findings are consistent with the previous studies in intrapersonal coordination.

Interaction of directional, neuromuscular and egocentric constraints on the stability of preferred bimanual coordination patterns

We investigated how the relative direction of limb movements in external space (iso- and non-isodirectionality), muscular constraints (the relative timing of homologous muscle activation) and the egocentric frame of reference (moving simultaneously toward/away the longitudinal axis of the body) contribute to the stability of coordinated movements. In the first experiment, we attempted to determine the respective stability of isodirectional and non-isodirectional movements in between-persons coordination. In a second experiment, we determined the effect of the relative direction in external space, and of muscular constraints, on pattern stability during a within-person bimanual coordination task. In the third experiment we dissociated the effects on pattern stability of the muscular constraints, relative direction and egocentric frame of reference. The results showed that (1) simultaneous activation of homologous muscles resulted in more stable performance than simultaneous activation of non-homologous muscles during within-subject coordination, and that (2) isodirectional movements were more stable than non-isodirectional movements during between-persons coordination, confirming the role of the relative direction of the moving limbs in the stability of bimanual coordination. Moreover, the egocentric constraint was to some extent found distinguishable from the effect of the relative direction of the moving limbs in external space, and from the effect of the relative timing of muscle activation. In summary, the present study showed that relative direction of the moving limbs in external space and muscular constraints may interact either to stabilize or destabilize coordination patterns.

Stability and skill in driving

Two experiments addressed the relation between postural stability, perceptual sensitivity, and stability of driving performance. A vehicle was fitted with differential GPS for measuring position and speed, position sensors for measuring brake and accelerator depression, force transducers for measuring door, console and footrest bracing forces, and an accelerometer for measuring the 3D accelerations of the vehicle. In Experiment 1, we investigated whether the initiation of deceleration and the control of braking might be due to sensitivity to the perceptual variable tau, which specifies time-to-contact (TTC), and in particular, whether its first derivative, tau-dot, is used to maintain a constant deceleration profile. Using both untrained experienced drivers (EDs) and trained driving instructors from the Holden Performance Driving Centre (HPDC), results confirmed that, regardless of skill level, tau-dot was maintained at a value close to 0.5 and, as predicted by Lee [Perception 5 (1976) 437], braking was initiated when TTC approximately 5 s. In Experiment 2, we wished to quantify the purported differences in driving behaviour between EDs and HPDC instructors during a variety of everyday manoeuvres. Results indicated that instructors utilised a different cornering trajectory, a different emergency braking strategy, and were able to perform a high-speed swerve and recovery task more effectively than the EDs. In general, the instructors applied greater bracing forces using the door and console compared with EDs. The instructors also applied greater footrest forces during emergency braking than did the EDs. The greater use of bracing by instructor drivers to resist g-forces represents a strategy of active stabilisation that enhances both postural stability, as well as overall stability and consistency of driving performance. Results are discussed with regard to the dynamics of perceptual-motor coordination, and how increased stability might improve sensitivity to relevant perceptual information. We conclude that driver-training programmes that focus on increasing driver stability (as a pre-requisite for increased control) show great promise as a means to improving one's attention during driving, and hence have the potential to dramatically improve road safety in general.

Intentional and attentional dynamics of speech-hand coordination

Interest is rapidly growing in the hypothesis that natural language emerged from a more primitive set of linguistic acts based primarily on manual activity and hand gestures. Increasingly, researchers are investigating how hemispheric asymmetries are related to attentional and manual asymmetries (i.e., handedness). Both speech perception and production have origins in the dynamical generative movements of the vocal tract known as articulatory gestures. Thus, the notion of a "gesture" can be extended to both hand movements and speech articulation. The generative actions of the hands and vocal tract can therefore provide a basis for the (direct) perception of linguistic acts. Such gestures are best described using the methods of dynamical systems analysis since both perception and production can be described using the same commensurate language. Experiments were conducted using a phase transition paradigm to examine the coordination of speech-hand gestures in both left- and right-handed individuals. Results address coordination (in-phase vs. anti-phase), hand (left vs. right), lateralization (left vs. right hemisphere), focus of attention (speech vs. tapping), and how dynamical constraints provide a foundation for human communicative acts. Predictions from the asymmetric HKB equation confirm the attentional basis of functional asymmetry. Of significance is a new understanding of the role of perceived synchrony (p-centres) during intentional cases of gestural coordination.

Practice-dependent modulation of neural activity during human sensorimotor coordination: a functional Magnetic Resonance Imaging study

We investigated the degree to which differences in the pattern of blood oxygen level dependent activity (BOLD) between syncopated and synchronized coordination patterns are altered by practice. Baseline levels of BOLD activity were obtained from eight subjects while they syncopated or synchronized with an auditory metronome at 1.25 Hz. Subjects then practiced syncopation at the same rate for four consecutive sessions. Post practice scans of the two coordination patterns were then performed. Before practice, baseline syncopation activated a much broader network of both cortical and subcortical regions than synchronization that included Supplementary Motor Area (SMA), bilateral putamen, left thalamus, bilateral superior temporal gyrus as well as the vermis. This pattern of activity is hypothesized to reflect the extra timing and attention requirements of syncopation. After practice, activity in superior temporal gyrus and vermis were no longer observed during syncopation reflecting a reduction in the need for attention and the use of sensory feedback for guiding behavior. Surprisingly, post practice synchronization resulted in additional significant activations in SMA, inferior frontal gyrus and superior temporal gyrus as well as small activations in bilateral putamen. Practice with the more difficult syncopation task thus had a dual effect of decreasing the number of active regions during syncopation and increasing the number of active regions during synchronization. Since overt syncopation performance did not change significantly as a result of practice, these observed neural changes appear to be due to context- and history-dependent factors, rather than behavioral learning per se.

Attentional demands reflect learning-induced alterations of bimanual coordination dynamics

This study aimed to investigate the effects of practice on bimanual coordination dynamics and attentional demands. Participants were asked to perform a dual-task associating a cyclic antiphase bimanual pattern and a discrete reaction time task. A pretest determined each individual critical transition frequency. In the training session, participants practised 120 trials. They were instructed to maintain the antiphase coordination pattern at the critical transition frequency. The training session was interrupted and followed by an intermediate test (after 60 trials) and a post-test (30 min after 120 trials), respectively. A retention test was performed 7 days after the end of the training session. Results showed that: (i) the number of transitions decreased as a consequence of practice; and (ii), subjects were able to maintain the antiphase pattern at a higher frequency than in the pretest. Analysis of the trade-off between relative phase variability and reaction time showed that participants were able to maintain a higher level of stability at the same (intermediate and post-test) or a lower attentional cost (retention test). These findings show that phase transition dynamics and pattern stability can be significantly modified as a result of practice. Changes in the trade-off between pattern stability and cost with learning confirm that the attentional cost incurred by the central nervous system to maintain pattern stability decreased with practice. In line with recent neurobiological studies, the present study provides new insights regarding relationships between brain processes, attentional demands and coordinated behaviour in learning bimanual patterns.

Effects of acute physical exercise characteristics on cognitive performance

The effect of physical exercise on mental function has been widely studied from the beginning of the 20th century. However, the contradictory findings of experimental research have led authors to identify several methodological factors to control in such studies including: (i) the nature of the psychological task; and (ii) the intensity and duration of physical exercise. The purpose of this article is to provide information, from the perspective of performance optimisation, on the main effects of physical task characteristics on cognitive performance. Within this framework, some consistent results have been observed during the last decade. Recent studies, using mainly complex decisional tasks, have provided the research community with clear support for an improvement of cognitive performance during exercise. Diverse contributing factors have been suggested to enhance cognitive efficacy. First, an increase in arousal level related to physical exertion has been hypothesised. Improvement in decisional performance has been observed immediately after the adrenaline threshold during incremental exercise. Such positive effects could be enhanced by nutritional factors, such as carbohydrate or fluid ingestion, but did not seem to be influenced by the level of fitness. Second, the mediating role of resource allocation has been suggested to explain improvement in cognitive performance during exercise. This effect highlights the importance of motivational factors in such tasks. Finally, when the cognitive performance was performed during exercise, consistent results have indicated that the dual task effect was strongly related to energetic constraints of the task. The greater the energy demand, the more attention is used to control movements.

The interplay of attention and bimanual coordination dynamics

Despite their common origin, studies on motor coordination and on attentional load have developed into separate fields of investigation, bringing out findings, methods, and theories which are diverse if not mutually exclusive. Sitting at the intersection of these two fields, this article addresses the issue of behavioral flexibility by investigating how intention modifies the stability of existing patterns of coordination between moving limbs. It addresses the issue, largely ignored until now, of the attentional cost incurred by the central nervous system (CNS) in maintaining a coordination pattern at a given level of stability, in particular under different attentional priority requirements. The experimental paradigm adopted in these studies provides an original mix of a classical measure of attentional load, namely, reaction time, and of a dynamic approach to coordination, most suitable for characterizing the dynamic properties of coordinated behavior and behavioral change. Findings showed that central cost and pattern stability covary, suggesting that bimanual coordination and the attentional activity of the CNS involved in maintaining such a coordination bear on the same underlying dynamics. Such a conclusion provides a strong support to a unified approach to coordination encompassing a conceptualization in terms of information processing and another, more recent framework rooted in self-organization theories and dynamical systems models.