Kids observing other kids' hands: visuomotor priming in children

We investigated motor resonance in children using a priming paradigm. Participants were asked to judge the weight of an object shortly primed by a hand in an action-related posture (grasp) or a non action-related one (fist). The hand prime could belong to a child or to an adult. We found faster response times when the object was preceded by a grasp hand posture (motor resonance effect). More crucially, participants were faster when the prime was a child's hand, suggesting that it could belong to their body schema, particularly when the child's hand was followed by a light object (motor simulation effect). A control experiment helped us to clarify the role of the hand prime. To our knowledge this is the first behavioral evidence of motor simulation and motor resonance in children. Implications of the results for the development of the sense of body ownership and for conceptual development are discussed.     

Response coding and visuomotor transformation in the Simon task: the role of action goals

Manual responses can be defined by differing response parameters. Any of them may generate a Simon effect. For all those response parameters, the same implementation of the Simon effect (in terms of subserving mechanism) is assumed. In 3 experiments, subjects had to respond with either fingers or sticks. Temporal properties of the Simon effect changed with response parameters relevant in a task. The Simon effect for manual responses decayed. For stick responses, in which the action goal differed from the anatomical mapping of the acting hand, a sustained Simon effect was observed. However, if the action goal for stick responses was not instrumental for selecting the correct response, the Simon effect decayed. The findings are consistent with the notion of different mechanisms involved in generating a Simon effect.     

Practice effects on visuomotor and problem-solving tests by children

Practice effects on a visuomotor test (the Developmental Test of Visuo-Motor Integration), a timed visual discrimination test (the Underlining Test), and two problem-solving tests (the Porteus Mazes Test and the Tower of Hanoi Test) were analyzed. Children of two age groups (Ms: 7.7 and 11.6 yr.) were chosen to study the effect of age on practice effects. The tests were repeated nine times with test-retest intervals of 2 mo. The Developmental Test of Visuo-Motor Integration showed no practice effects, while the Porteus Mazes Test, the Underlining Test, and the Tower of Hanoi Test showed significant practice effects. Practice effects were larger for the older age group on all the tests, except the Developmental Test of Visuo-Motor Integration. The Developmental Test of Visuo-Motor Integration and the Underlining Test showed good reliability, but those of the problem-solving tasks were less satisfactory. The stability of all the tests, except the Tower of Hanoi Test, was good.     

Catching skills in infancy

Infants were induced to reach for fast moving objects whose velocity and starting position varied. Altogether, 144 reaches were analyzed by a technique that took into consideration the three-dimensional properties of reaches. It was found that reaches in all conditions were aimed close to the meeting point with the object. The precision in timing of a reach was about a twentieth of a second, and the systematic timing errors were close to zero. The results suggest that the infant reaches in reference to a coordinate system fixed to the moving object instead of to the static background, that is, the infant's hand is moved with the object at the same time as it is moved toward the object. It is concluded that the capacity to time and coordinate one's movements in the catching of a moving object is a very basic and early developed skill.     

Nonlinear visuomotor transformations: Locus and modularity

Participants in two experiments moved a mouse-like device to the right to move a cursor on a computer screen to a target position. The cursor was invisible during motion but reappeared at the end of each movement. The relationship between the amplitudes of the cursor movement and the mouse movement was exponential in Experiment 1 and logarithmic in Experiment 2 for two groups of participants, while it was linear for the control groups in both experiments. The results of both experiments indicate that participants adjusted well to the external transformation by developing an internal model that approximated the inverse of the external transformation. We introduce a method to determine the locus of the internal model. It indicates that the internal model works at a processing level that either preceded specification of movement amplitude, or had become part of movement amplitude specification. Limited awareness of the nonlinear mouse–cursor relationship and the fact that a working-memory task had little effect on performance suggest that the internal model is modular and not dependent on high-level cognitive processes.     

Nonlinear visuomotor transformations: locus and modularity

Participants in two experiments moved a mouse-like device to the right to move a cursor on a computer screen to a target position. The cursor was invisible during motion but reappeared at the end of each movement. The relationship between the amplitudes of the cursor movement and the mouse movement was exponential in Experiment 1 and logarithmic in Experiment 2 for two groups of participants, while it was linear for the control groups in both experiments. The results of both experiments indicate that participants adjusted well to the external transformation by developing an internal model that approximated the inverse of the external transformation. We introduce a method to determine the locus of the internal model. It indicates that the internal model works at a processing level that either preceded specification of movement amplitude, or had become part of movement amplitude specification. Limited awareness of the nonlinear mouse-cursor relationship and the fact that a working-memory task had little effect on performance suggest that the internal model is modular and not dependent on high-level cognitive processes.     

Abrupt, but not gradual visuomotor distortion facilitates adaptation in children with developmental coordination disorder

A previous experiment investigating visuomotor adaptation in typically developing children and children with Developmental Coordination Disorder (DCD) suggested poor adaptation to an abruptly induced visuomotor perturbation. In the current study, using a similar center-out drawing task, but administering either an abrupt or a gradual perturbation, and twice as many adaptation trials, we show that typically developing children are well able to successfully update an existing internal model in response to a 60 degrees rotation of the visual feedback, independent of the perturbation condition. Children with DCD, however, updated their internal map more effectively during exposure to an abrupt visuomotor perturbation than to a gradual one. This may suggest that the adaptation process in children with DCD responds differently to small vs. large steps of visuomotor discrepancies. Given the known role of the cerebellum in providing an error signal necessary for updating the internal model in response to a gradual visuomotor distortion, the results of our study add to the growing body of evidence implicating compromised cerebellar function in DCD.     

The visuomotor mental rotation task: visuomotor transformation times are reduced for small and perceptually familiar angles

In the visuomotor mental rotation (VMR) task, participants point to a location that deviates from a visual cue by a predetermined angle. This task elicits longer reaction times (RT) relative to tasks wherein the visual cue is spatially compatible with the movement goal. The authors previously reported that visuomotor transformations are faster and more efficient when VMR responses elicit a degree of dimensional overlap (i.e., 0° and 5°) or when the transformation involves a perceptually familiar angle (i.e., 90° or 180°; K. A. Neely & M. Heath, 2010b). One caveat to this finding is that standard and VMR responses were completed in separate blocks of trials. Thus, between-task differences not only reflect the temporal demands of the visuomotor transformations, but also reflect the temporal cost of response inhibition. The goal of this study was to isolate the time cost of visuomotor transformations in the VMR task. The results demonstrated that visuomotor transformations are more efficient and effective when the response entails a degree of dimensional overlap between target and response (i.e., when the angular disparity between the responses is small) or when the transformation angle is perceptually familiar.     

Dynamic visuomotor synchronization: Quantification of predictive timing

When a moving target is tracked visually, spatial and temporal predictions are used to circumvent the neural delay required for the visuomotor processing. In particular, the internally generated predictions must be synchronized with the external stimulus during continuous tracking. We examined the utility of a circular visual-tracking paradigm for assessment of predictive timing, using normal human subjects. Disruptions of gaze–target synchronization were associated with anticipatory saccades that caused the gaze to be temporarily ahead of the target along the circular trajectory. These anticipatory saccades indicated preserved spatial prediction but suggested impaired predictive timing. We quantified gaze–target synchronization with several indices, whose distributions across subjects were such that instances of extremely poor performance were identifiable outside the margin of error determined by test–retest measures. Because predictive timing is an important element of attention functioning, the visual-tracking paradigm and dynamic synchronization indices described here may be useful for attention assessment.     

Dynamic action in virtual environments: Constraints on the accessibility of action knowledge in children and adults

In a series of three experiments, we probed the accessibility of action knowledge in different versions of a virtual environment (VE) with 7-year-old children and adults. Using a PHANToM^TM haptic interface, participants performed a virtual throwing task in which they tried to propel a ball from a table to hit a target on the ground. In Experiments 1 and 2, the virtual scene was presented on a computer monitor, and, in Experiment 3, it was projected by using a video projector so that the vertical and horizontal dimensions and the spatial location of the VE corresponded to the real-world dimensions. Results indicate that action knowledge is accessible even in a nonimmersive VE, but also suggest that the need to recalibrate perceptual-motor mappings constrains the accessibility of this kind of intuitive knowledge.     

Dynamic action in virtual environments: constraints on the accessibility of action knowledge in children and adults

In a series of three experiments, we probed the accessibility of action knowledge in different versions of a virtual environment (VE) with 7-year-old children and adults. Using a PHANToM haptic interface, participants performed a virtual throwing task in which they tried to propel a ball from a table to hit a target on the ground. In Experiments 1 and 2, the virtual scene was presented on a computer monitor, and, in Experiment 3, it was projected by using a video projector so that the vertical and horizontal dimensions and the spatial location of the VE corresponded to the real-world dimensions. Results indicate that action knowledge is accessible even in a nonimmersive VE, but also suggest that the need to recalibrate perceptual-motor mappings constrains the accessibility of this kind of intuitive knowledge.     

Visuoperceptual and visuomotor deficits in developmental stutterers: an exploratory study

Although the cause of stuttering is unknown, there is strong evidence for it being a neuromotor disorder characterised by an abnormality of higher control encompassing not only speech but other motor systems. The aim of this exploratory study was to look for the presence of non-speech/language deficits--in particular, visuomotor and visuoperceptual deficits--in persons who stutter. Twelve moderate to severe developmental stutterers were compared with a group of fluent speakers, matched for age and sex, on a range of computerized sensory-motor tasks. These tasks covered various aspects of visuomotor function--ballistic movement, dynamic steadiness, and several types of tracking--and visuoperceptual function--acuity, static perception, and dynamic perception. A novel technique was used to remove the visuospatial component from tracking performance. Stutterers had slower reaction times, less accurate random tracking, and impaired dynamic visual perception. Severity of stuttering correlated with reaction time and dynamic perception. Removal of the visuoperceptual component from tracking performance indicated that the impaired tracking in the stutterers was predominantly due to reduced dynamic perception. This is the first study to provide preliminary evidence for the presence of non-linguistic visuoperceptual and upper-limb visuomotor tracking deficits in people with moderate to severe stuttering. These findings support a neurogenic aetiology for stuttering and are compatible with evidence of an overactive dopamine system in stutterers.     

Interventions for children of divorce: toward greater integration of research and action.

A number of child-, family-, and system-focused interventions have been designed to prevent or reduce the negative effects of divorce on children. This article critically evaluates these intervention efforts by examining (a) their relation to basic research on the processes proposed to mediate children's postdivorce adjustment and (b) evaluation studies assessing the effectiveness of various programs. Although interventions address some of the factors proposed to mediate children's adaptation to divorce, the interplay between interventions and basic research on children's postdivorce adaptation is limited. Moreover, some intervention efforts appear to be beneficial, but most lack empirical documentation of their efficacy. This analysis leads to several recommendations for basic and applied research and for improving the response of the mental health field to the problems experienced by many children from divorcing families.     

Decay in visuomotor representations during manual aiming

The time course of the decay of spatial representations used for planning and controlling manual aiming has not been established. The authors' purpose in the present investigation was to generate a psychometric function for memory-guided reaching movements. Eight university-aged students performed a reciprocal tapping task for 10 s. Participants could see the targets for 5 s; then, vision of the targets was occluded. The present findings provide mixed support for 2 prominent theories concerning memory representations. Variability increased concurrently with the removal of vision of the targets, supporting the real-time hypothesis. However, a brief plateau in the curve was apparent for approximately 2 s after vision was removed, consistent with the use of a highly accurate representation for action.     

Sex differences and effects of aging on visuomotor coordination.

The purpose of this study was to examine the effects of aging on men and women in processing information required to reproduce direction and distance on a visuomotor task. Subjects (45 men and 45 women) selected from three age groups (25-34 yr., 45-54 yr., 65-74 yr.) were required to estimate blindly the exact criterion location of a target-point they had identified under one of the following conditions: visual, kinesthetic, and visuokinesthetic. Errors in direction (degrees) and in distance (cm) were recorded. The analysis of the total variability in responding (E) indicated that the women of the 65- to 74-yr. age group were significantly less accurate in estimating distance than were the men of the two older age groups (45 to 54 yr., 65 to 74 yr.) and less accurate than were the women of the 25- to 34-yr. age group. No significant differences in estimating distance were found among the three age groups of men. No significant differences for direction were found between men and women.     

Movement adaptations in 7- to 10-year-old typically developing children: evidence for a transition in feedback-based motor control

We used a modified double-step pointing task to study movement adaptations in 7- to 10-year-old typically developing children. We found that the majority (63%) were able to optimally adapt fast, goal-directed visually-guided movements to a late change in target location meeting the requirements of speed and accuracy. A minority (35%) failed to meet the requirement of accuracy resulting in a less optimal adaptation. The results showed that the ability to adapt movements optimally develops before the age of 7 years in typically developing children. Literature proposes a transition in development of motor control around the age of 8 years. The present results replicate and extend this by suggesting that this transition affects the later phases of fast, goal-directed visually-guided movements rather than the early phases, such as movement programming and acceleration. Finally, the results indicate that the optimally adapted movements were the result of a specific strategy in which a specific component of movement execution was slowed on all trials. This suggests that 7- to 10-year-old typically developing children have developed implicit knowledge about which movement components are the most efficient to adapt.     

Dual-tasking alleviated sleep deprivation disruption in visuomotor tracking: an fMRI study

Effects of dual-responding on tracking performance after 49-h of sleep deprivation (SD) were evaluated behaviorally and with functional magnetic resonance imaging (fMRI). Continuous visuomotor tracking was performed simultaneously with an intermittent color-matching visual detection task in which a pair of color-matched stimuli constituted a target and non-matches were non-targets. Tracking error means were binned time-locked to stimulus onset of the detection task in order to observe changes associated with dual-responding by comparing the error during targets and non-targets. Similar comparison was made with fMRI data. Our result showed that despite a significant increase in the overall tracking error post SD, from 20 pixels pre SD to 45 pixels post SD, error decreased to a minimum of about 25 pixels 0-6s after dual-response. Despite an overall reduced activation post SD, greater activation difference between targets and non-targets was found post SD in task-related regions, such as the left cerebellum, the left somatosensory cortex, the left extrastriate cortex, bilateral precuneus, the left middle frontal gyrus, and the left motor cortex. Our results suggest that dual-response helps to alleviate performance impairment usually associated with SD. The duration of the alleviation effect was on the order of seconds after dual-responding.     

Alternate response preparation in a visuomotor serial task

The preparation of a particular motor pattern is related to the information available that enables the actor to predict the correct response to a forthcoming stimulus. In many situations, however, prediction is not possible. In such cases, the individual can guess the probable parameters of the next stimulus. The authors attempted to establish the bias in the motor intention for movement and its interaction with a possible memory trace of the stimulus-response mapping produced by the preceding stimulus. Two letters were presented bilaterally, and participants (N=21) had to discriminate the target letter and respond with the compatible hand. The present findings support the existence of a memory trace of the previous stimulus-response mapping.