Postural adaptations to a suprapostural memory task among children with and without developmental coordination disorder

Aim The present study investigated the effects of varying the cognitive demands of a memory task (a suprapostural task) while recording postural motion on two groups of children, one diagnosed with developmental coordination disorder (DCD) and an age‐matched group of typically developing children. Method Two groups, each comprising 38 child volunteers (21 males, 17 females) aged 9 to 10 years, participated in the study. Each child performed a digital memory task at two levels of difficulty, low and high. Positional variability (standard deviation of position) of the head and torso were recorded as the biomechanical responses to the variation in task difficulty. Results Both groups significantly reduced postural motion when engaged in the high‐difficulty condition (p<0.05) compared with the low‐difficulty condition. Children with DCD exhibited significantly higher levels of postural motion (p<0.05) than the typically developing children. The typically developing children significantly reduced their postural motion in the high‐difficulty condition (p<0.05) compared with the low‐difficulty condition, whereas children with DCD did not. Interpretation Our results suggest that the postural responses of children with DCD differ from those of typically developing children while engaging in a memory task with various levels of difficulty.     

Automaticity and attention in Huntington's disease: When two hands are not better than one

People with Huntington's disease (HD) commonly report difficulty carrying out two everyday tasks simultaneously. This difficulty, confirmed by experimental studies, is typically ascribed to impaired attention. Yet, dual-task problems extend to relatively simple tasks, such as walking and talking, which would ordinarily be considered relatively undemanding of attention. The study tests the hypothesis that in HD there is a deficit in the ability to automatise task performance. Thus, simple tasks, which place minimal demands on conscious attention in healthy controls, make disproportionately high demands on attentional resources in HD. We examined the performance of HD patients and healthy controls on a simple, paced finger-tapping task, comparing single-task (tapping with one hand) and dual-task (tapping with both hands simultaneously) performance. For HD patients, bimanual tapping increased the task demands: there was greater variability in tapping rate and patients reported that the ‘dual-task’ condition was more difficult. The opposite pattern was observed for controls. Variability in tapping performance in HD was highly correlated with performance on cognitive tasks that have the potential to be automatised but not with performance on tasks that are more demanding of executive control, suggesting a common substrate for cognitive and motor automaticity. The data support the hypothesis that HD patients are impaired in their capacity for automisation, and suggest that impaired automaticity may be one source of attentional deficits in HD. The findings have implications for the interpretation of ‘high level’ deficits in attention and executive function previously reported in HD.     

Behavioral data and neural correlates for postural prioritization and flexible resource allocation in concurrent postural and motor tasks

This study was undertaken to investigate the reciprocity effect between postural and suprapostural performances and its underlying neural mechanisms wherein subjects executed a perceptual‐motor suprapostural task and maintained steady upright postures. Fourteen healthy individuals conducted force‐matching maneuvers (static vs. dynamic) under two stance conditions (bipedal stance vs. unipedal stance); meanwhile, force‐matching error, center of pressure dynamics, event‐related potentials (ERPs), and the movement‐related potential (MRP) were monitored. The behavioral results showed that force‐matching error and postural sway were differently modulated by variations in stance pattern and force‐matching version. Increase in postural challenge undermined the precision of static force‐matching but facilitated a dynamic force‐matching task. Both static and dynamic force‐matching tasks improved postural control of unipedal stance but not of bipedal stance, in reference to the control conditions. ERP results revealed a stance‐dependent N1 response, which was greater around the parietal cortex in the unipedal stance conditions. Instead, P2 was modulated by the effect of the suprapostural motor task, with a smaller P2 in the right parietal cortex for dynamic force‐matching. Spatiotemporal evolution of the MRP commenced at the left frontal‐central area and spread bilaterally over the frontal‐central and parietal cortex. MRP onset was subject to an analogous interaction effect on force‐matching performance. Our findings suggest postural prioritization and a structural alternation effect of stance pattern on postural performance, relevant to implicit expansion and selective allocation of central resources for relative task‐loads of a postural‐suprapostural task. Hum Brain Mapp, 2013. © 2011 Wiley Periodicals, Inc.     

Inverse relation between postural variability and difficulty of a concurrent short-term memory task

We measured postural stability while participants simply stood or stood while performing a digit rehearsal task of varying levels of difficulty in order to examine the effects on postural control of concurrent short-term memory demands. The rehearsal task manipulation avoided factors that contaminate postural sway measurements, such as vocal articulation or visual fixation during posture data collection. When participants performed the more difficult digit tasks (longer digit strings), postural sway was reduced relative to when performing an easy version of the task (few digits). The results identified a complex relation between postural control and cognitive or attentional demands.     

Head–torso–hand coordination in children with and without developmental coordination disorder

Aim This study investigated the nature of coordination and control problems in children with developmental coordination disorder (DCD). Method Seven adults (two males, five females, age range 20–28y; mean 23y, SD 2y 8mo) and eight children with DCD (six males, two females, age range 7–9y; mean 8y, SD 8mo), and 10 without DCD (seven males, three females, age range 7–9y; mean 8y, SD 7mo) sat in a swivel chair and looked at or pointed to targets. Optoelectronic apparatus recorded head, torso, and hand movements, and the spatial and temporal characteristics of the movements were computed. Results Head movement times were longer (p<0.05) in children with DCD than in the comparison group, even in the looking task, suggesting that these children experience problems at the lowest level of coordination (the coupling of synergistic muscle groups within a single degree of freedom). Increasing the task demands with the pointing condition affected the performance of children with DCD to a much greater extent than the other groups, most noticeably in key feedforward kinematic landmarks. Temporal coordination data indicated that all three groups attempted to produce similar movement patterns to each other, but that the children with DCD were much less successful than age‐matched children in the comparison group. Interpretation Children with DCD have difficulty coordinating and controlling single degree‐of‐freedom movements; this problem makes more complex tasks disproportionately difficult for them. Quantitative analysis of kinematics provides key insights into the nature of the problems faced by children with DCD.     

Association between visual perceptual deficits and motor deficits in children with developmental coordination disorder

This study explored the relation between a motor-free visual perceptual deficit, different visual-motor integration deficits, and different motor skills in children with developmental coordination disorder (DCD). Thirty-six children (22 males), aged 9 or 10 years, with DCD and a control group (n=36), matched for age and sex, were assessed with the Movement Assessment Battery for Children (MABC), a ball-catching test, a jumping test, a timed response task to a visual moving stimulus, and the Beery-Buktenica Developmental Test of Visual-Motor Integration, incorporating copying, visual discrimination, and tracing tasks. Children with DCD performed significantly worse than the control group on all measures. The visual discrimination task did not correlate significantly with any of the motor tasks. The visual timing task correlated significantly with the ball-catching test in the DCD group. The copying test was significantly correlated with the MABC in the DCD group. The association between visual-perceptual deficits and motor tasks was shown to be task specific.     

Cognitive-motor interference during fine and gross motor tasks in children with Developmental Coordination Disorder (DCD)

BackgroundWhile typically developing children produce relatively automatized postural control processes, children with DCD seem to exhibit an automatization deficit. Dual tasks with various cognitive loads seem to be an effective way to assess the automatic deficit hypothesis.AimsThe aims of the study were: (1) to examine the effect of a concurrent cognitive task on fine and gross motor tasks in children with DCD, and (2) to determine whether the effect varied with different difficulty levels of the concurrent task.Methods and proceduresWe examined dual-task performance (Trail-Making-Test, Trail-Walking-Test) in 20 children with DCD and 39 typically developing children. Based on the idea of the Trail-Making-Test, participants walked along a fixed pathway, following a prescribed path, delineated by target markers of (1) increasing sequential numbers, and (2) increasing sequential numbers and letters. The motor and cognitive dual-task effects (DTE) were calculated for each task.ResultsRegardless of the cognitive task, children with DCD performed equally well in fine and gross motor tasks, and were slower in the dual task conditions than under single task-conditions, compared with children without DCD. Increased cognitive task complexity resulted in slow trail walking as well as slower trail tracing. The motor interference for the gross motor tasks was least for the simplest conditions and greatest for the complex conditions and was more pronounced in children with DCD. Cognitive interference was low irrespective of the motor task.Conclusions and implicationsChildren with DCD show a different approach to allocation of cognitive resources, and have difficulties making motor skills automatic. The latter notion is consistent with impaired cerebellar function and the “automatization deficit hypothesis”, suggesting that any deficit in the automatization process will appear if conscious monitoring of the motor skill is made more difficult by integrating another task requiring attentional resources.     

Attention demand and postural control in children with hearing deficit

To elucidate the mechanisms responsible for deteriorated postural control in children with hearing deficit (CwHD), we measured center-of-pressure (COP) variability, mean velocity and entropy in bipedal quiet stance (feet together) with or without the concurrent cognitive task (reaction to visual stimulus) on hard or foam surface in 29 CwHD and a control group of 29 typically developing children (CON). The CwHD displayed an overall decreased postural performance as compared to the CON in the medial-lateral plane (p < 0.05). Standing on foam pad revealed slower simple reaction time in the CwHD (p < 0.05) while the results on hard surface were not different. The CwHD decreased (p < 0.05) the amount of attention invested in posture during dual task which accounted for the need of more cognitive resources to handle two tasks simultaneously than controls. It was unmistakable that the intergroup differences emerged when the tasks performed were relatively novel and untrained: feet together, foam pad, and reaction time. All these tasks, while being very easy for the CON, made the CwHD deteriorate postural or cognitive performance. These results unravel the difficulty in reaching the consecutive developmental stages in the CwHD and call for specific therapeutic modalities that might facilitate this development.     

Neurobiological bases and neurophysiological correlates of developmental coordination disorders

Among psychomotor disorders in children, developmental coordination disorder (DCD) is characterized by a motor skill impairment that interferes with psychomotor development, academic performance and activities of daily living, despite normal intelligence. The main behavioural phenomena (lack of postural control, coordination and motor learning) suggest involvement of cerebellum, basal ganglia and frontal and parietal lobes. Our studies on a synchronisation/syncopation task, with EEG recording (coherence analysis and evoked potential), show that DCD children (8 to 12 years old) exhibit major interindividual variability and do not improve performance with repetition. In younger DCD children, an increase of coherence between fronto-central regions was reported, and, for evoked potential, an increase of motor preparation component and a N100 latency longer than control children. These findings support the idea of a general synchronization disorder in DCD children and furnish elements allowing a better understanding of intra- and interindividual variability.     

Slowed muscle force production and sensory organization deficits contribute to altered postural control strategies in children with developmental coordination disorder

This study aimed to (1) compare the postural control strategies, sensory organization of balance control, and lower limb muscle performance of children with and without developmental coordination disorder (DCD) and (2) determine the association between postural control strategies, sensory organization parameters and knee muscle performance indices among children with DCD. Fifty-eight DCD-affected children and 46 typically developing children participated in the study. Postural control strategies and sensory organization were evaluated with the sensory organization test (SOT). Knee muscle strength and time to produce maximum muscle torque (at 180°/s) were assessed using an isokinetic machine. Analysis of variance was used to compare the outcome variables between groups, and multiple regression analysis was used to examine the relationships between postural control strategies, sensory organization parameters, and isokinetic indices in children with DCD. The DCD group had significantly lower strategy scores (SOT conditions 5 and 6), lower visual and vestibular ratios, and took a longer time to reach peak torque in the knee flexor muscles than the control group (p > 0.05). After accounting for age, sex, and body mass index, the vestibular ratio explained 35.8% of the variance in the strategy score of SOT condition 5 (p < 0.05). Moreover, the visual ratio, vestibular ratio, and time to peak torque of the knee flexors were all significant predictors (p < 0.05) of the strategy score during SOT condition 6, accounting for 14, 19.7, and 19.8% of its variance, respectively. The children with DCD demonstrated deficits in postural control strategy, sensory organization and prolonged duration of muscle force development. Slowed knee muscle force production combined with poor visual and vestibular functioning may result in greater use of hip strategy by children with DCD in sensory challenging environments.     

Cross-Modal Attention-Switching is Impaired in Autism Spectrum Disorders

This investigation aimed to determine if children with ASD are impaired in their ability to switch attention between different tasks, and whether performance is further impaired when required to switch across two separate modalities (visual and auditory). Eighteen children with ASD (9–13?years old) were compared with 18 typically-developing children matched with the ASD group for mental age, and also with 18 subjects with learning difficulties matched with the ASD group for mental and chronological age. Individuals alternated between two different visual tasks, and between a different visual task and an auditory task. Children with ASD performed worse than both comparison groups at both switching tasks. Moreover, children with ASD had greater difficulty when different modalities were required than where only one modality was required in the switching task in comparison with participants matched in terms of mental and chronological age.     

Mathematical difficulties in developmental coordination disorder: Symbolic and nonsymbolic number processing

At school, children with Developmental Coordination Disorder (DCD) struggle with mathematics. However, little attention has been paid to their numerical cognition abilities. The goal of this study was to better understand the cognitive basis for mathematical difficulties in children with DCD.Twenty 7-to-10 years-old children with DCD were compared to twenty age—matched typically developing children using dot and digit comparison tasks to assess symbolic and nonsymbolic number processing and in a task of single digits additions.Results showed that children with DCD had lower performance in nonsymbolic and symbolic number comparison tasks than typically developing children. They were also slower to solve simple addition problems. Moreover, correlational analyses showed that children with DCD who experienced greater impairments in the nonsymbolic task also performed more poorly in the symbolic tasks.These findings suggest that DCD impairs both nonsymbolic and symbolic number processing. A systematic assessment of numerical cognition in children with DCD could provide a more comprehensive picture of their deficits and help in proposing specific remediation.     

Role of attentional resources on gait performance in Huntington's disease

Patients with Huntington's disease (HD) suffer from cognitive deficits with impaired executive functions, including limited attentional resources. We sought to use a dual‐task paradigm to evaluate attentional demands and the ability of patients with HD to concentrate on two tasks simultaneously. We analyzed the interference effects of cognitive and motor tasks on walking in HD and the contribution of clinical symptoms to gait disturbances. Patients and controls were asked to perform either a motor task (carrying a tray with four glasses), a cognitive task (counting backwards), or no task at all while walking at their preferred speed. Kinematic spatial parameters, temporal parameters, and angular parameters related to gait were recorded in 15 patients and 15 controls by means of a videomotion analysis system. Gait instability was assessed using the stride‐to‐stride variability of the various gait parameters. For patients with HD, performing a concurrent cognitive task resulted in a lower gait speed (compared with free walking), with decreased cadence and stride length. However, this effect was not observed in controls. Performing a motor task did not change any kinematic gait parameters in either HD or control subjects. We found correlations between gait speed in the dual cognitive/walking task on one hand and the motor UHDRS score, cognitive status and executive function on the other. Patients with HD had greater difficulty walking while performing a concurrent cognitive task; the drain on attentional resources deteriorated walking performance. © 2007 Movement Disorder Society     

Visual–proprioceptive mapping in children with developmental coordination disorder

Developmental coordination disorder (DCD) occurs in a small but significant proportion of children who present with impaired body-eye coordination and show poor acquisition of motor skills. This study investigated the visual-proprioceptive mapping ability of children with DCD from a small selected group, with particular reference to the use of vision in matching tasks. The children with DCD in this study were significantly poorer than control children on all matching tasks. They seemed to have particular difficulty in cross-modal judgements that required the use of visual information to guide proprioceptive judgements of limb position. A distinction is drawn between tasks that can be achieved purely through sensory matching and those that require body-centred spatial judgements, suggesting that it is the latter that posits a particular difficulty for children with DCD.     

Dual-task study of cognitive and postural interference in 7-year-olds and adults

The study examined, in children aged 7 and adults, the postural control when a cognitive task (modified Stroop) of varying level of difficulty is executed simultaneously. Postural difficulty also varied (with or without vibrations of the ankle joint). We hypothesized that children's performance was more affected than adults', when the difficulty of the cognitive and postural tasks increased. Results (i) demonstrated that the presence of a concurrent cognitive task affected postural sway at all ages; (ii) confirmed that the interference between mental activity and postural control can be attributed mainly to general capacity limitations and (iii) showed a degradation of the postural criteria in children but not of the cognitive ones, when the postural condition was constraining.     

Statistically characterizing intra- and inter-individual variability in children with Developmental Coordination Disorder

Previous research investigating children with Developmental Coordination Disorder (DCD) has consistently reported increased intra- and inter-individual variability during motor skill performance. Statistically characterizing this variability is not only critical for the analysis and interpretation of behavioral data, but also may facilitate our understanding of the processes underlying DCD. Thus, the primary purpose of this research was to demonstrate the utility of a flexible statistical technique, a random coefficient model (RCM), that characterizes the increased intra- and inter-individual variability in children with and without DCD. We analyzed data from a sensorimotor adaptation task during which participants executed discrete aiming movements under conditions of rotated visual feedback. To highlight the advantages of this statistical approach, we contrasted the results from the RCM with those from a traditionally employed general linear model (GLM). The RCM revealed differences between the two groups of children that the GLM did not detect; and, characterized trajectories of change for each individual. The RCM provides researchers an opportunity to probe behavioral deficits at the individual level and may provide new insights into the behavioral heterogeneity in children with DCD.     

Neural Correlates of Explicit Versus Implicit Facial Emotion Processing in ASD

The underlying neural mechanisms of implicit and explicit facial emotion recognition (FER) were studied in children and adolescents with autism spectrum disorder (ASD) compared to matched typically developing controls (TDC). EEG was obtained from N?=?21 ASD and N?=?16 TDC. Task performance, visual (P100, N170) and cognitive (late positive potential) event-related-potentials, as well as coherence were compared across groups. TDC showed a task-dependent increase and a stronger lateralization of P100 amplitude during the explicit task and task-dependent modulation of intra-hemispheric coherence in the beta band. In contrast, the ASD group showed no task dependent modulation. Results indicate disruptions in early visual processing and top-down attentional processes as contributing factors to FER deficits in ASD.     

Visual tasks and postural sway in children with and without autism spectrum disorders

We investigated the influences of two different suprapostural visual tasks, visual searching and visual inspection, on the postural sway of children with and without autism spectrum disorder (ASD). Sixteen ASD children (age = 8.75 ± 1.34 years; height = 130.34 ± 11.03 cm) were recruited from a local support group. Individuals with an intellectual disability as a co-occurring condition and those with severe behavior problems that required formal intervention were excluded. Twenty-two sex- and age-matched typically developing (TD) children (age = 8.93 ± 1.39 years; height = 133.47 ± 8.21 cm) were recruited from a local public elementary school. Postural sway was recorded using a magnetic tracking system (Flock of Birds, Ascension Technologies, Inc., Burlington, VT). Results indicated that the ASD children exhibited greater sway than the TD children. Despite this difference, both TD and ASD children showed reduced sway during the search task, relative to sway during the inspection task. These findings replicate those of Stoffregen et al. (2000), Stoffregen, Giveans, et al. (2009), Stoffregen, Villard, et al. (2009) and Prado et al. (2007) and extend them to TD children as well as ASD children. Both TD and ASD children were able to functionally modulate postural sway to facilitate the performance of a task that required higher perceptual effort.     

Postural sway changes during static standing with concurrent task in children with traumatic brain injury

Objectives:To investigate the effects of concurrent tasks (motor and cognitive) on postural control performance in children with traumatic brain injury (TBI) compared to typically developing (TD) control subjects.Methods:Sixteen children with TBI (aged 11.63±1.89 years) and 22 TD controls (aged 11.41±2.24 years) participated in this case-control study. This study was conducted between May 2016 and March 2017. Each child performed static standing under 3 different conditions: single, concurrent motor, and concurrent cognitive task. Postural control performance measure includes sway area, anterior-posterior (AP) sway velocity, medio-lateral (ML) sway velocity, AP sway distance and ML sway distance as measured using the APDM® Mobility Lab (Oregon, Portland). A repeated-measure analysis of variance was used to analyse the data.Results:We found that children with TBI showed significantly more deterioration in postural control performance than TD children (p<0.05). Both concurrent tasks (motor and cognitive) significantly decreased postural control performance in both groups with more pronounced changes in children with TBI than that of the TD controls.Conclusion:The results demonstrated that, performing concurrent tasks (motor and cognitive) during upright standing resulted in deterioration of postural control performance. The existence of cognitive and balance impairment in children with TBI will possibly cause concurrent tasks to be more complex and demands greater attention compared to single task.

Traumatic brain injury is frequently referred to as a ‘silent epidemic’, with the majority of society being unaware on the magnitude a TBI can cause on an individual’s function.1 It remains a leading cause of death and long-term disability in children worldwide with approximately 3 million children experiencing TBI annually.2 Consequently, TBI may lead to neurological impairment which contributes to long-term disability among this group of children.With the cognitive and behavioral deficit, individuals with TBI are faced with a long-term functional disability including postural control instability.3,4 Postural control refers to the act of maintaining, achieving or restoring the line of gravity or centre of mass (COM) within the base of support (BOS).5 It is a complex collaboration of sensory, motor, and central nervous system. Disruption of any components such as visual, vestibular sensory inputs, muscle weakness and loss of proprioception will result in postural control instability. This impairment could seriously interfere with the child’s level of independence and lead to increased risk of falls.5The maintenance and control of posture and balance, whether in static or dynamic conditions, are essential requirements for daily activity. Postural control requires a lot of cognitive resources.6 The more challenging postural task required more cognitive processing in order to sustain the position. Children with TBI have both cognitive and information processing deficits that impact attention and functional abilities.7,8 In daily life, children encounter situations in which they must perform cognitive and motor tasks simultaneously, such as responding to verbal instructions or manipulating objects while sitting or standing. These situations may be complex and challenging for children with TBI as they present with both attention and information processing deficit. Using dual-task methodology, it can examine the effect of adding a concurrent task during a motor task. Trials using dual-task paradigm are commonly used in a clinical setting to measure automatic control of movement indirectly. It is crucial to understand the effects of a concurrent task on postural control performance while designing a dual-task paradigm intervention program in this population. The dual-task intervention during postural control could be more challenging and may improve the postural stability better as compared to single task intervention.Since attention is a limited resource, it may become overloaded by competing for attention demands and subsequently might lead to reduced performance in one or all tasks.9 Children with TBI may need more attention during postural control and as a result might be more vulnerable to falls while doing concurrent task. A recent study among healthy children and youth 5-18 years old showed concurrent cognitive task resulted in decreased postural stability.10 Comparing the effects of different surface (firm vs. foam surface) on postural stability during concurrent cognitive task reveals that the foam surface caused greater interference in postural stability.10 A normative database was created as a result of this study, which may benefit future investigations of post-concussion performances with potential to assess post-concussion severity. In addition, it also focuses on assessing both motor and cognitive domains simultaneously. This study also reports information regarding the effect of cognitive task on postural stability in healthy children & youth. The examined effect of concurrent cognitive and motor task conditions on postural control in children with TBI is limited. Therefore, the objective of the present study was to investigate the postural control performance under concurrent tasks in children with TBI and TD controls. We hypothesized that both concurrent motor and cognitive tasks would cause significant postural control deterioration compared to single task condition.     

New insights into feature and conjunction search: II. Evidence from Alzheimer's disease

Deficits in inefficient visual search task performance in Alzheimer's disease (AD) have been linked both to a general depletion of attentional resources and to a specific difficulty in performing conjunction discriminations. It has been difficult to examine the latter proposal because the uniqueness of conjunction search as compared to other visual search tasks has remained a matter of debate. We explored both these claims by measuring pupil dilation, as a measure of resource application, while patients with AD performed a conjunction search task and two single-feature search tasks of similar difficulty in healthy individuals. Maximum pupil dilation in the AD group was greater during performance of the conjunction than the feature search tasks, although pupil response was indistinguishable for the three tasks in healthy controls. This, together with patients' false positive errors for the conjunction task, indicates an AD-specific deficit impacting upon the ability to combine information on multiple dimensions. In addition, maximum pupil dilation was no less for patients than the control group during task performance, which tends to oppose the concept of general resource depletion in AD. However, eye movement patterns in the patient group indicated that they were less able than controls to use organised strategies to assist with task performance. The data are therefore in keeping with a loss of access to resource-saving strategies, rather than a loss of resources per se, in AD. Moreover they demonstrate an additional processing mechanism in performing conjunction search compared with inefficient single-feature search.