Timing at peak force may be the hidden target controlled in continuation and synchronization tapping.

Timing control, such as producing movements at a given rate or synchronizing movements to an external event, has been studied through a finger-tapping task where timing is measured at the initial contact between finger and tapping surface or the point when a key is pressed. However, the point of peak force is after the time registered at the tapping surface and thus is a less obvious but still an important event during finger tapping. Here, we compared the time at initial contact with the time at peak force as participants tapped their finger on a force sensor at a given rate after the metronome was turned off (continuation task) or in synchrony with the metronome (sensorimotor synchronization task). We found that, in the continuation task, timing was comparably accurate between initial contact and peak force. These two timing events also exhibited similar trial-by-trial statistical dependence (i.e., lag-one autocorrelation). However, the central clock variability was lower at the peak force than the initial contact. In the synchronization task, timing control at peak force appeared to be less variable and more accurate than that at initial contact. In addition to lower central clock variability, the mean SE magnitude at peak force (SEP) was around zero while SE at initial contact (SEC) was negative. Although SEC and SEP demonstrated the same trial-by-trial statistical dependence, we found that participants adjusted the time of tapping to correct SEP, but not SEC, toward zero. These results suggest that timing at peak force is a meaningful target of timing control, particularly in synchronization tapping. This result may explain the fact that SE at initial contact is typically negative as widely observed in the preexisting literature.

Preparing future faculty and professionals for public health careers.

Recent years have brought rapid growth in schools of public health and an increasing demand for public health practitioners. These trends highlight the need for innovative approaches to prepare doctoral graduates for academic and high-level practice positions. The University of Maryland's School of Public Health developed a "Preparing Future Faculty and Professionals" program to enrich the graduate education and professional development of its doctoral students. We describe the program's key elements, including foundational seminars to enhance students' knowledge and skills related to teaching, research, and service; activities designed to foster career exploration and increase competitiveness in the job market; and independent, faculty-mentored teaching and research experiences. We present a model for replicating the program and share student outcomes of participation.

Development of kinesthetic-motor and auditory-motor representations in school-aged children.

In two experiments using a center-out task, we investigated kinesthetic-motor and auditory-motor integrations in 5- to 12-year-old children and young adults. In experiment 1, participants moved a pen on a digitizing tablet from a starting position to one of three targets (visuo-motor condition), and then to one of four targets without visual feedback of the movement. In both conditions, we found that with increasing age, the children moved faster and straighter, and became less variable in their feedforward control. Higher control demands for movements toward the contralateral side were reflected in longer movement times and decreased spatial accuracy across all age groups. When feedforward control relies predominantly on kinesthesia, 7- to 10-year-old children were more variable, indicating difficulties in switching between feedforward and feedback control efficiently during that age. An inverse age progression was found for directional endpoint error; larger errors increasing with age likely reflect stronger functional lateralization for the dominant hand. In experiment 2, the same visuo-motor condition was followed by an auditory-motor condition in which participants had to move to acoustic targets (either white band or one-third octave noise). Since in the latter directional cues come exclusively from transcallosally mediated interaural time differences, we hypothesized that auditory-motor representations would show age effects. The results did not show a clear age effect, suggesting that corpus callosum functionality is sufficient in children to allow them to form accurate auditory-motor maps already at a young age.

Training oncology and palliative care clinical nurse specialists in psychological skills: evaluation of a pilot study.

OBJECTIVE: National guidelines in the United Kingdom recommend training Clinical Nurse Specialists in psychological skills to improve the assessment and intervention with psychological problems experienced by people with a cancer diagnosis (National Institute for Health and Clinical Excellence, 2004). This pilot study evaluated a three-day training program combined with supervision sessions from Clinical Psychologists that focused on developing skills in psychological assessment and intervention for common problems experienced by people with cancer. METHODS: Questionnaires were developed to measure participants' levels of confidence in 15 competencies of psychological skills. Participants completed these prior to the program and on completion of the program. Summative evaluation was undertaken and results were compared. In addition, a focus group interview provided qualitative data of participants' experiences of the structure, process, and outcomes of the program. RESULTS: Following the program, participants rated their confidence in psychological assessment and skills associated with providing psychological support as having increased in all areas. This included improved knowledge of psychological theories, skills in assessment and intervention and accessing and using supervision appropriately. The largest increase was in providing psycho-education to support the coping strategies of patients and carers. Thematic analysis of interview data identified two main themes including learning experiences and program enhancements. The significance of the clinical supervision sessions as key learning opportunities, achieved through the development of a community of practice, emerged. SIGNIFICANCE OF RESULTS: Although this pilot study has limitations, the results suggest that a combined teaching and supervision program is effective in improving Clinical Nurse Specialists' confidence level in specific psychological skills. Participants' experiences highlighted suggestions for refinement and development of the program. Opportunities for further research and developments in this area are discussed.

Differences in movement-related cortical activation patterns underlying motor performance in children with and without developmental coordination disorder.

Behavioral deficits in visuomotor planning and control exhibited by children with developmental coordination disorder (DCD) have been extensively reported. Although these functional impairments are thought to result from "atypical brain development," very few studies to date have identified potential neurological mechanisms. To address this knowledge gap, electroencephalography (EEG) was recorded from 6- to 12-yr-old children with and without DCD (n = 14 and 20, respectively) during the performance of a visuomotor drawing task. With respect to motor performance, typically developing (TD) children exhibited age-related improvements in key aspects of motor planning and control. Although some children with DCD performed outside this TD landscape (i.e., age-related changes within the TD group), the group developmental trajectory of the children with DCD was similar to that of the TD children. Despite overall similarities in performance, engagement of cortical resources in the children with DCD was markedly different from that in their TD counterparts. While the patterns of activation are stable in TD children across the age range, the young children with DCD exhibited less engagement of motor cortical brain areas and the older children with DCD exhibited greater engagement of motor cortical brain areas than their TD peers. These results suggest that older children with DCD may employ a compensatory strategy in which increased engagement of relevant motor resources allows these children to perform comparably to their TD peers. Moreover, the magnitude of activation was related to several kinematic measures, particularly in children with DCD, suggesting that greater engagement in motor resources may underlie better behavioral performance.

Development of state estimation explains improvements in sensorimotor performance across childhood.

Previous developmental research examining sensorimotor control of the arm in school-age children has demonstrated age-related improvements in movement kinematics. However, the mechanisms that underlie these age-related improvements are still unclear. This study hypothesized that changes in sensorimotor performance across childhood can be attributed, in part, to the development of state estimation, defined as estimates computed by the central nervous system, which specify both current and future hand positions and velocities (i.e., hand "state"). Two behavioral experiments were conducted, in which 6- to 12-year-old children and young adults executed goal-directed arm movements. Results from Experiment 1 revealed that young children (i.e., ∼6-8 years) have less precise proprioceptive feedback for static (i.e., stationary) hand state estimation compared with older children (i.e., ∼10-12 years), resulting in increased variability of target-directed reaching movements. Experiment 2 demonstrated that young children rely on delayed and unreliable state estimates during the execution of goal-directed hand movements (i.e., dynamic state estimation), resulting in both increased movement errors and directional variability. Collectively, these results suggest that improvements in sensorimotor behavior across childhood can be attributed, at least partially, to the development of both static and dynamic state estimation.

Developmental delay of finger torque control in children with developmental coordination disorder.

AIM: We examined whether the behavioral impairments in finger torque control evident in children with developmental coordination disorder (DCD) follow a delayed or different developmental trajectory compared with their typically developing peers. METHOD: Children with DCD (n=36; 18 males, 18 females; mean age 9y 7mo, SD 1y 8mo) and 36 typically developing children (15 males, 21 females; mean age 9y 7mo, SD 2y), between 6 years 10 months and 12 years 7 months of age were recruited from schools in Porto Alegre, Brazil. Particpants completed finger torque control and maximum finger torque production tasks. The inclusion criterion for children with DCD was a Movement Assessment Battery for Children score below the fifth centile. Group means and cross-sectional age-related landscapes of the two groups were compared. RESULTS: Children with DCD were more variable (p<0.001), less accurate (p=0.007), and less irregular (p<0.001), on average, in their finger torque control than their typically developing peers, despite producing nearly equivalent levels of maximum torque (p=0.49). Despite these mean differences, the cross-sectional age-related changes in torque control were similar in the two groups (all p>0.05). INTERPRETATION: The developmental trajectory of finger torque control in children with DCD, compared with typically developing children, is delayed. This suggests the behavioral deficits in finger torque control in children with DCD persist as a function of age, rather than progressing or resolving.

Electrocortical dynamics reflect age-related differences in movement kinematics among children and adults.

Previous neuroimaging and behavioral studies demonstrated structural and functional changes in the motor system across childhood. However, it is unclear what functionally relevant electrocortical processes underlie developmental differences in motor planning and control during multijoint, goal-directed movements. The current study characterized age-related differences in electrocortical processes during the performance of discrete aiming movements in children and adults. Electroencephalography and movement kinematics were recorded from 3 groups of participants (n = 15 each): young children (mean 6.7 years), older children (mean 10.2 years), and adults (mean 22.1 years). Age-related differences were evident in the electroencephalographic (EEG) signals. First, young children exhibited less movement-related activity in task-relevant motor areas compared with adults (movement-related cortical potentials). Second, young children exhibited greater activation (less alpha power) of the frontal areas and less activation of the parietal areas as compared with the other groups. At the behavioral level, young children made slower and jerkier movements, with less consistent directional planning compared with older children and adults. Significant correlations were also found between EEG and movement kinematic measures. Taken together, the results of this study provide evidence that age-related differences in the quality of motor planning and performance are reflected in the differences in electrocortical dynamics among children and adults.

Beyond age and gender: relationships between cortical and subcortical brain volume and cognitive-motor abilities in school-age children.

There is growing evidence that cognitive and motor functions are interrelated and may rely on the development of the same cortical and subcortical neural structures. However, no study to date has examined the relationships between brain volume, cognitive ability, and motor ability in typically developing children. The NIH MRI Study of Normal Brain Development consists of a large, longitudinal database of structural MRI and performance measures from a battery of neuropsychological assessments from typically developing children. This dataset provides a unique opportunity to examine relationships between the brain and cognitive-motor abilities. A secondary analysis was conducted on data from 172 children between the ages of 6 to 13 years with up to 2 measurement occasions (initial testing and 2-year follow-up). Linear mixed effects modeling was employed to account for age and gender effects on the development of specific cortical and subcortical volumes as well as behavioral performance measures of interest. Above and beyond the effects of age and gender, significant relationships were found between general cognitive ability (IQ) and the volume of subcortical brain structures (cerebellum and caudate) as well as spatial working memory and the putamen. In addition, IQ was found to be related to global and frontal gray matter volume as well as parietal gray and white matter. At the behavioral level, general cognitive ability was also found to be related to visuomotor ability (pegboard) and executive function (spatial working memory). These results support the notion that cognition and motor skills may be fundamentally interrelated at both the levels of behavior and brain structure.

Multisensory adaptation of spatial-to-motor transformations in children with developmental coordination disorder.

Recent research has demonstrated that adaptation to a visuomotor distortion systematically influenced movements to auditory targets in adults and typically developing (TD) children, suggesting that the adaptation of spatial-to-motor transformations for reaching movements is multisensory (i.e., generalizable across sensory modalities). The multisensory characteristics of these transformations in children with developmental coordination disorder (DCD) have not been examined. Given that previous research has demonstrated that children with DCD have deficits in sensorimotor integration, these children may also have impairments in the formation of multisensory spatial-to-motor transformations for target-directed arm movements. To investigate this hypothesis, children with and without DCD executed discrete arm movements to visual and acoustic targets prior to and following exposure to an abrupt visual feedback rotation. Results demonstrated that the magnitudes of the visual aftereffects were equivalent in the TD children and the children with DCD, indicating that both groups of children adapted similarly to the visuomotor perturbation. Moreover, the influence of visuomotor adaptation on auditory-motor performance was similar in the two groups of children. This suggests that the multisensory processes underlying adaptation of spatial-to-motor transformations are similar in children with DCD and TD children.

NCS Assessments of the Motor, Sensory, and Physical Health Domains.

As part of the National Children's Study (NCS) comprehensive and longitudinal assessment of the health status of the whole child, scientific teams were convened to recommend assessment measures for the NCS. This manuscript documents the work of three scientific teams who focused on the motor, sensory, or the physical health aspects of this assessment. Each domain team offered a value proposition for the importance of their domain to the health outcomes of the developing infant and child. Constructs within each domain were identified and measures of these constructs proposed. Where available extant assessments were identified. Those constructs that were in need of revised or new assessment instruments were identified and described. Recommendations also were made for the age when the assessments should take place.

Beyond the mean reaction time: Trial-by-trial reaction time reveals the distraction effect on perceptual-motor sequence learning.

Perceptual-motor sequences can be learned quickly under distraction, often demonstrated by the mean reaction time (RT) change in a serial reaction time (SRT) task. However, any arbitrary mean RT can arise from one of many distinct trial-by-trial RT patterns. It is surprising that previous sequence learning studies have hinged only on the mean RT metrics while little is known about the distraction effect on its trial-by-trial processes. In an SRT task with or without distraction, we found that initially learning a fixed repeating sequence without distraction was expressed by a micro-online learning process where reaction time (RT) progressively improved within learning blocks as adults continuously performed the SRT task. Such online RT improvements, however, vanished when the SRT task was performed under distraction. Despite the detrimental effect of distraction on micro-online RT improvements, we observed offline enhancements in RT following rest intervals of 3 min that emerged to secure sequence learning under distraction. We reasoned that distraction may exert influence on the micro-online and offline learning by mediating the engagement of explicit and implicit memory. Given the offline RT change under distraction, a short rest between learning blocks may be a key player in early perceptual-motor sequence learning under distraction. We thus suggest that future studies investigating the distraction effect on sequence learning need to control the length of rest between learning blocks, while previous research with equivocal interpretations of the distraction effect failed to do so.

Temporal variability in continuous versus discontinuous drawing for children with Developmental Coordination Disorder.

Children with Developmental Coordination Disorder (DCD) are reported to have high temporal variability in tasks requiring precise timing. The current study examined whether this timing deficit was due to the cerebellar 'explicit timing' process in the discontinuous, but not the continuous movement. Ten children with DCD and 31 typically developing children performed continuous, discontinuous circle and line drawing tasks. Results showed that both children with DCD and their age-matched controls had higher temporal variability in the discontinuous than that in the continuous movements. Individual comparisons between each child with DCD and the performance of typically developing children revealed that 2 out of 10 children with DCD showed limited timing deficit in both types of discontinuous drawing (lines and circles). Additionally, three different children with DCD had timing problems with only discontinuous line drawing. Thus, the possibility of a compromised cerebellar function may exist in a subgroup of children with DCD. This work raises a critical issue with respect to the functional heterogeneity of this population and emphasizes the importance of an individualized analysis in this movement disorder.

The development of infant upright posture: sway less or sway differently?

Postural control is an important factor for early motor development; however, compared with adults, little is known about how infants control their unperturbed upright posture. This lack of knowledge, particularly with respect to spatial and temporal characteristics of infants' unperturbed independent standing, represents a significant gap in the understanding of human postural control and its development. Therefore, our first analysis offers a thorough longitudinal characterization of infants' quiet stance through the 9 months following the onset of independent walking. Second, we examined the influence of sensory-mechanical context, light touch contact, on infants' postural control. Nine typically developing infants were tested monthly as they stood on a small pedestal either independently or with the right hand lightly touching a stationary contact surface. In addition to the longitudinal study design, an age-constant sample was analyzed to verify the influence of walking experience in infant postural development without the confounding effect of chronological age. Center of pressure excursions were recorded and characterized by distance-related, velocity, and frequency domain measures. The results indicated that, with increasing experience in the upright, as indexed by walk age, infants' postural sway exhibited shifts in rate-related characteristics toward lower frequency and slower, less variable velocity oscillations without changing the spatial characteristics of sway. Additional touch contact stabilized infants' postural sway as revealed by decrease in sway position variance, amplitude, and area as well as lower frequency and velocity. These results were confirmed by the age-constant analysis. Taken together, our findings suggest that instead of progressively reducing the sway magnitude, infants sway differently with increasing upright experience or with additional somatosensory information. These differences suggest that early development of upright stance, particularly as it relates to increasing postural and locomotor experience, involves a refinement of sensorimotor dynamics that enhances estimation of self-motion for controlling upright stance.

Age-related changes in multi-finger interactions in adults during maximum voluntary finger force production tasks.

This study aimed to continue our characterization of finger strength and multi-finger interactions across the lifespan to include those in their 60s and older. Building on our previous study of children, we examined young and elderly adults during isometric finger flexion and extension tasks. Sixteen young and 16 elderly, gender-matched participants produced maximum force using either a single finger or all four fingers in flexion and extension. The maximum voluntary finger force (MVF), the percentage contributions of individual finger forces to the sum of individual finger forces during four-finger MVF task (force sharing), and the non-task finger forces during a task finger MVF task (force enslaving), were computed as dependent variables. Force enslaving during finger extension was greater than during flexion in both young and elderly groups. The flexion-extension difference was greater in the elderly than the young adult group. The greater independency in flexion may result from more frequent use of finger flexion in everyday manipulation tasks. The non-task fingers closer to a task finger produced greater enslaving force than non-task fingers farther from the task finger. The force sharing pattern was not different between age groups. Our findings suggest that finger strength decreases over the aging process, finger independency for flexion increases throughout development, and force sharing pattern remains constant across the lifespan.

Multi-limb coordination and rhythmic variability under varying sensory availability conditions in children with DCD.

Children with Developmental Coordination Disorder (DCD) have sensory processing deficits; how do these influence the interface between sensory input and motor performance? Previously, we found that children with DCD were less able to organize and maintain a gross motor coordination task in time to an auditory cue, particularly at higher frequencies [Whitall, J., Getchell, N., McMenamin, S., Horn, C., Wilms-Floet, A., & Clark, J. (2006). Perception-action coupling in children with and without DCD: Frequency locking between task relevant auditory signals and motor responses in a dual motor task. Child: Care, Health, and Development, 32, 679-692]. In the present study, we examine the same task (clapping in-phase to marching on a platform) under conditions involving the removal of vision and hearing. Eleven children with DCD (mean=7.21, SD=0.52 years), 7 typically developing (TD) children (mean=6.95+/-0.72 years), and 10 adults performed continuous clapping while marching under four conditions: with vision and hearing, without vision, without hearing, and without both. Results showed no significant condition effects for any measure taken. The DCD group was more variable in phasing their claps and footfalls than both the adult group and the TD group. There were also significant group effects for inter-clap interval coefficient of variation and inter-footfall interval coefficient of variation, with the DCD group being the most variable for both measures. Coherence analysis between limb combinations (e.g., left arm-right arm, right arm-left leg) revealed that the adults exhibited significantly greater coherence for each combination than both of the children's groups. The TD group showed significantly greater coherence than the DCD group for every limb combination except foot-foot and left hand-right foot. Measures of approximate entropy indicated that adults differed from children both with and without DCD in the structure of the variability across a trial with adults showing more complexity. Children with DCD are able to accomplish a self-initiated gross-motor coordination task but with increased variability for most but not all measures compared to typically developing children. The availability of visual and/or auditory information does not play a significant role in stabilizing temporal coordination of this task, suggesting that these are not salient sources of information for this particular task.

Continuous and discontinuous drawing: high temporal variability exists only in discontinuous circling in young children.

The authors studied whether the drawing variability in young children is best explicable by (a) demands on the explicit timing system, (b) an underdeveloped ability to control limb dynamics, or (c) both. The explicit timing demands were lower in continuous drawing in comparison with the discontinuous task. The authors manipulated limb dynamics by changing the number of joints involved, with line drawing requiring fewer joints than circle drawing. Results showed that young children had high temporal variability in discontinuous circling but not in other conditions. The authors argue that both explicit timing and dynamic complexity of limb control may be determinants of temporal consistency and may thus play an important role in the development of drawing and writing skills in children.

A Perception-Action Approach to Understanding Typical and Atypical Motor Development.

In this chapter, we ask two questions. First, can the study of the perception-action system across time offer a useful model for understanding motor development? Second, can the study of the perception-action system in children with developmental coordination disorder (DCD) inform our understanding of atypical as well as typical motor development? We begin by describing the dynamical systems perspective and a control-theoretic approach that together provide the conceptual framework for our paradigms, methodology, and interpretation of our experiments. Our experimental strategy has been to perturb one or more sensory systems and observe the effect on the motor system. The majority of the chapter explains how we employed two principal perturbation strategies: (1) removing or adding a static source of sensory information believed to be salient to the task at hand and (2) enhancing a dynamic source of sensory information either implicitly or explicitly. These strategies were employed in three different action systems: posture; rhythmic interlimb coordination, and goal-directed reaching and drawing. After synthesizing our findings, we conclude by addressing the original questions and offering future directions. In brief, we consider that perception-action coupling is an underlying mechanism/foundation/constraint of motor development in the sense that the ongoing processing of sensations and the planning and execution of movements are how the brain produces goal-directed movements. Therefore, a better understanding of how this coupling changes or adapts over time has much to offer as to how motor behavior develops across the lifespan, both typically and atypically.

The "Motor" in Implicit Motor Sequence Learning: A Foot-stepping Serial Reaction Time Task.

This protocol describes a modified serial reaction time (SRT) task used to study implicit motor sequence learning. Unlike the classic SRT task that involves finger-pressing movements while sitting, the modified SRT task requires participants to step with both feet while maintaining a standing posture. This stepping task necessitates whole body actions that impose postural challenges. The foot-stepping task complements the classic SRT task in several ways. The foot-stepping SRT task is a better proxy for the daily activities that require ongoing postural control, and thus may help us better understand sequence learning in real-life situations. In addition, response time serves as an indicator of sequence learning in the classic SRT task, but it is unclear whether response time, reaction time (RT) representing mental process, or movement time (MT) reflecting the movement itself, is a key player in motor sequence learning. The foot-stepping SRT task allows researchers to disentangle response time into RT and MT, which may clarify how motor planning and movement execution are involved in sequence learning. Lastly, postural control and cognition are interactively related, but little is known about how postural control interacts with learning motor sequences. With a motion capture system, the movement of the whole body (e.g., the center of mass (COM)) can be recorded. Such measures allow us to reveal the dynamic processes underlying discrete responses measured by RT and MT, and may aid in elucidating the relationship between postural control and the explicit and implicit processes involved in sequence learning. Details of the experimental set-up, procedure, and data processing are described. The representative data are adopted from one of our previous studies. Results are related to response time, RT, and MT, as well as the relationship between the anticipatory postural response and the explicit processes involved in implicit motor sequence learning.