Contribution of stereopsis,vergence, and accommodative function to the performance of a precision grasping and placement task in typically developing children age 8–14 years

Upper limb reaching and grasping movements are performed more efficiently during binocular viewing; however, the distinct contribution of stereopsis, fusional vergence, and accommodation (binocular facility, amplitude and accuracy) has not been examined in typically developing children. This study examined binocular visual function in a cohort of 57 typically developing children, 8 to 14 years old. Hand kinematics were recorded using a motion capture camera while children performed a prehension task involving threading a bead onto a needle. Results showed that different aspects of binocular vision contribute to the control of distinct phases of upper limb movements. Specifically, fusional vergence was associated with higher peak reach velocity, stereoacuity was associated with shorter grasp execution, and accommodation was associated with shorter placement duration. These findings suggest that different aspects of binocular vision play an important role in optimizing the control of distinct phases of prehension movements during development.     

Development of eye-hand coordination in typically developing children and adolescents assessed using a reach-to-grasp sequencing task

Eye-hand coordination is required to accurately perform daily activities that involve reaching, grasping and manipulating objects. Studies using aiming, grasping or sequencing tasks have shown a stereotypical temporal coupling pattern where the eyes are directed to the object in advance of the hand movement, which may facilitate the planning and execution required for reaching. While the temporal coordination between the ocular and manual systems has been extensively investigated in adults, relatively little is known about the typical development of eye-hand coordination. Therefore, the current study addressed an important knowledge gap by characterizing the profile of eye-hand coupling in typically developing school-age children (n = 57) and in a cohort of adults (n = 30). Eye and hand movements were recorded concurrently during the performance of a bead threading task which consists of four distinct movements: reach to bead, grasp, reach to needle, and thread. Results showed a moderate to high correlation between eye and hand latencies in children and adults, supporting that both movements were planned in parallel. Eye and reach latencies, latency differences, and dwell time during grasping and threading, showed significant age-related differences, suggesting eye-hand coupling becomes more efficient in adolescence. Furthermore, visual acuity, stereoacuity and accommodative facility were also found to be associated with the efficiency of eye-hand coordination in children. Results from this study can serve as reference values when examining eye and hand movement during the performance of fine motor skills in children with neurodevelopmental disorders.     

Comparison of upper limb kinematics in two activities of daily living with different handling requirements

IntroductionRecently, kinematic analysis of the drinking task (DRINK) has been recommended to assess the quality of upper limb (UL) movement after stroke, but the accomplishment of this task may become difficult for poststroke patients with hand impairment. Therefore, it is necessary to study ADLs that involve a simpler interaction with a daily life target, such as the turning on a light task (LIGHT). As the knowledge of movement performed by healthy adults becomes essential to assess the quality of movement of poststroke patients, the main goal of this article was to compare the kinematic strategies used by healthy adults in LIGHT with those that are used in DRINK.Methods63 adults, aged 30 to 69 years old, drank water and turned on a light, using both ULs separately, while seated. The movements of both tasks were captured by a 3D motion capture system. End-point and joint kinematics of reaching and returning phases were analysed. A multifactorial analysis of variance with repeated measures was applied to the kinematic metrics, using age, sex, body mass index and dominance as main factors.ResultsMean and peak velocities, index of curvature, shoulder flexion and elbow extension were lower in LIGHT, which suggests that the real hand trajectory was smaller in this task. In LIGHT, reaching was less smooth and returning was smoother than DRINK. The instant of peak velocity was similar in both tasks. There was a minimal anterior trunk displacement in LIGHT, and a greater anterior trunk displacement in DRINK. Age and sex were the main factors which exerted effect on some of the kinematics, especially in LIGHT.ConclusionThe different target formats and hand contact in DRINK and LIGHT seem to be responsible for differences in velocity profile, efficiency, smoothness, joint angles and trunk displacement. Results suggest that the real hand trajectory was smaller in LIGHT and that interaction with the switch seems to be less demanding than with the glass. Accordingly, LIGHT could be a good option for the assessment of poststroke patients without grasping ability. Age and sex seem to be the main factors to be considered in future studies for a better match between healthy and poststroke adults.     

Posture-movement responses to stance perturbations and upper limb fatigue during a repetitive pointing task

Localized muscle fatigue and postural perturbation have separately been shown to alter whole-body movement but little is known about how humans respond when subjected to both factors combined. Here we sought to quantify the kinematics of postural control and repetitive upper limb movement during standing surface perturbations and in the presence of fatigue. Subjects stood on a motion-based platform and repetitively reached between two shoulder-height targets until noticeably fatigued (rating of perceived exertion = 8/10). Every minute, subjects experienced a posterior and an anterior platform translation while reaching to the distal target. Outcomes were compared prior to and with fatigue (first vs. final minute data). When fatigued, regardless of the perturbation condition, subjects decreased their shoulder abduction and increased contralateral trunk flexion, a strategy that may relieve the load on the fatiguing upper limb musculature. During perturbations, kinematic adaptations emerged across the trunk and arm to preserve task performance. In contrast to our expectation, the kinematic response to the perturbations did not alter in the presence of fatigue. Kinematic adaptations in response to the perturbation predominantly occurred in the direction of the reach whereas fatigue adaptations occurred orthogonal to the reach. These findings suggest that during repetitive reaching, fatigue and postural perturbation compensations organize so as to minimize interaction with each other and preserve the global task characteristics of endpoint motion.     

Reliability of upper extremity kinematics while performing different tasks in individuals with stroke

Assessments of upper extremity performance typically include qualitative rather than quantitative measures of functional ability. Kinematic analysis is an objective, discriminative measure that quantifies movement biomechanics; however, the use within the poststroke impaired upper extremity is not well established. The purpose of this study was to examine the reliability of upper extremity kinematics in 18 individuals with stroke and 9 healthy controls. Participants performed reaching and grasping tasks over 2 separate days and metrics included movement time, peak velocity, index of curvature, trunk displacement, maximum aperture, and percentage of the movement cycle where maximum aperture occurred. The results showed moderate to high intraclass correlation and low standard error of measurement values for most variables, demonstrating that kinematic analysis may be a feasible and useful tool to quantify upper extremity movement after stroke.     

Prehension in children and adults: The effects of object size

Studies of visually goal-directed arm movements in adults have shown that various task constraints such as intention, context, and object properties affect different kinematic characteristics of the movement components (Jeannerod, 1984; MacKenzie et al., 1987; Marteniuk et al., 1987, 1990; Paulignan et al., 1991; Soechting, 1984). The purpose of the present study was to compare the effects of varying object size on the kinematics of reaching and grasping in both children and adults. Five children aged 9–10 years and five adults aged 18–24 years reached for and grasped three different sized cubes. Results revealed that object size had the same effect on the planning and control of reaching and grasping movements in children as in adults. Unlike adults, however, children in this age range spent more time in deceleration and reached peak aperture much later in the movement trajectory. The results were interpreted as immature integration of the visual and proprioceptive systems in 9–10 year olds. The implications of these findings for further examining developmental trends in prehension are discussed.PsycINFO classification: 2330     

The development of reaching behavior in low-risk preterm infants

This longitudinal study investigated the development of reaching behavior in the seated position in preterm infants at the ages of 5–7 months by analyzing kinematic variables (straightness and adjustment indexes, movement unit, mean and final velocities). The correlation between kinematic variables and grasping was verified. The participants were nine low-risk preterm infants with no cerebral lesions. Ten fullterm infants served as control. In both groups, kinematic variables remained unchanged over age, except for the adjustment index, which was higher at 6 months in the preterm group. Successful grasping increased in both groups over age and it was shown to be negatively correlated with mean velocity in the preterm infants. At the ages of 6 and 7 months, preterms showed lower mean and final velocities and higher adjustment index when compared with fullterms. The relative constancy in the kinematic variables suggests that, after having explored the action possibilities during the acquisition phase, the infants selected an adaptative pattern to perform the reaching movements. Slower movements and greater adjustments may be functional strategies of preterms to achieve successful grasps.     

Evidence of motor planning in infant reaching behavior

When adults reach for an object, kinematic measures of their approach movement are affected by what they intend to do after grasping it. We examined whether such future intended actions would be reflected in the approach-to-grasp phase of infant reaching. Twenty-one 10-month-old infants were encouraged to either throw a ball into a tub or fit it down a tube. Kinematic measures of the approach phase of the reach toward the ball were obtained using a motion analysis system. Infants, like adults, reached for the ball faster if they were going to subsequently throw it as opposed to using it in the precision action. The perceptual aspects of the ball were the same and cannot account for these kinematic differences. Infants appear to be planning both segments of their actions in advance. Our findings provide evidence for a level of sophistication in infant motor planning not reported before.     

Development of infant reaching behaviors: Kinematic changes in touching and hitting

This longitudinal study investigated the development of reaching in typical infants, from age 4 to 8 months, and described the pattern of hand kinematics underlying changes in the characteristics of infants’ actions while reaching for a target. Thirteen infants were followed biweekly. Two reaching behaviors emerged during the infants’ free interactions with the target, touching and hitting. Changes over time were documented for the number of movement units, straightness index, distance, peak velocity and time to peak velocity of the hand for touches and hits. We observed increases in the numbers of touches and hits and changes in hand kinematics over time; the distance traveled by the hand was greater for hitting compared to touching. These kinematic changes were specific to the movement patterns that infants adopted to reach to the target.     

Effects of Object Texture on Precontact Movement Time in Human Prehension

Using kinematic data in a precision-grip reaching task, Weir, MacKenzie, Marteniuk, and Cargoe (1991) concluded that prior to contact with an object, its texture does not affect the course of grasping. The present study used their task of reaching for and lifting a slippery-, normal- (polished metal), or rough-surfaced dowel. This occurred under the original, blocked condition, in which textures were held constant within a series of trials, and under a new, randomized condition, in which textures varied randomly from trial to trial. Performance was also examined over more extended periods of practice. Reaction time and precontact movement time were directly measured. In contrast to the results of Weir et al., 1991, reaching for the slippery dowel resulted in slower movement time. This effect was found both early and late in practice for the randomized condition; it was found only in late practice for the blocked condition. These effects can be attributed to the greater geometric and dynamic precision required for lifting a slippery object.     

The development of rapid online control in children aged 6–12 years: Reaching performance

Rapid online control during reaching has an important bearing on movement accuracy and flexibility. It is surprising then that few studies have investigated the development of rapid online control in children. In this study, we were particularly interested in age-related changes in the nature of motor control in response to visual perturbation. We compared the performance of younger (6–7 years of age), mid-aged (8–9), and older (10–12) children, as well as healthy young adults using a double-step reaching task. Participants were required to make target-directed reaching movements in near space, while also responding to visual perturbations that occurred at movement onset for a small percentage of trials. Results showed that both the older and mid-aged children corrected their reaching in response to the unexpected shifts in target location significantly faster than younger children, manifest by reduced time to correction. In turn, the responses of adults were faster than older children in terms of movement time and on kinematic measures such as time to correction and time to peak velocity. These results indicate that the capacity to utilize forward estimates of limb position in the service of online control of early perturbations to ballistic (or rapid) reaching develops in a non-linear fashion, progressing rapidly between early and middle childhood, showing a degree of stability over mid and later childhood, but then evidence for continued refinement between childhood and young adulthood. The pattern of change after childhood and into early adolescence requires further investigation, particularly during the rapid phase of physical growth that accompanies puberty.     

Dissecting online control in Developmental Coordination Disorder: a kinematic analysis of double-step reaching

In a recent study, children with movement clumsiness (or Developmental Coordination Disorder-DCD) were shown to have difficulties making rapid online corrections when reaching, demonstrated by slower and less accurate movements to double-step targets (Hyde & Wilson, 2011). These results suggest that children with DCD have difficulty using predictive estimates of limb position when making rapid adjustments to movement, in-flight. However, chronometric data alone does not provide strong evidence for this hypothesis: it remains unclear whether early (and rapid) control parameters or post-correction stages of the movement trajectory are affected. Thus, the overarching aim of this study was to conduct a kinematic analysis of double-step reaching in order to isolate the different control parameters that might explain the slower and less accurate double-step reaching performance of children with DCD. Participants were a new sample of 13 children with DCD aged between 8-12 years and 13 age-matched controls. Children were required to reach and touch one of three possible targets presented at the coordinates -20°, 0° and 20° on a 17 in. LCD touch-screen. For most trials (80%) the target remained stationary for the duration of movement (non-jump trials), while for the remainder (20%), the target jumped randomly to one of two peripheral locations at movement onset (jump trials). Consistent with earlier work, children with DCD were slower to initiate reaching compared to controls and showed longer MT and more errors on jump trials. Kinematic data showed that while the two groups did not differ on time to peak velocity or acceleration, children with DCD were slower to correct reach trajectory on jump trials. No group differences were observed on late kinematic markers, e.g., post-correction time. The pattern of results support and extend earlier work showing deficits in ROC in DCD. From a computational perspective, delayed corrections to the reach trajectory suggests some difficulty integrating information about the target perturbation with a predictive (or forward) estimate of limb position relative to the initial target. These conclusions are discussed, along with directions for future research.     

Gait and reach-to-grasp movements are mutually modified when performed simultaneously

Typically, prehension and gait behaviors are studied separately. However, little is known about what changes occur in these motor skills when they are combined. We investigated and characterized motor performance during combined walking and prehension at different levels of difficulty of the prehension task. Fifteen right-handed young adults were invited to walk at their self-selected pace and grasp a dowel as they walked. They also grasped the dowel in a stationary condition (upright stance). We combined conditions with/without obstacles and stable/unstable base for dowel prehension. Modifications in gait and prehension were identified when they were combined, especially for the most difficult prehension conditions. The grasping task caused an adaptation in gait because the participants preferred to adopt a more conservative strategy of increasing their dynamic stability during the approach phase and when grasping the dowel. Walking changed the prehension movement by reducing the reaching movement time, peak wrist velocity, and peak grip aperture velocity. In addition, the peak grip aperture was affected by the presence of obstacles close to the dowel. The participants adjusted their gait during the approach phase to facilitate dowel prehension, and they controlled the hand position online to adjust its configuration based on the prehension conditions.     

Kinematic form and scaling: further investigations on the visual perception of lifted weight

Observers are able to judge accurately the weight lifted by another person when only the motions of reflective patches attached to the lifter's major limb joints and head can be seen (Runeson & Frykholm, 1981). What properties of these complex kinematic patterns allow judgments of weight to be made? The pattern of variation in velocity of the lifted object over position is explored as a source of information for weight: It is found to provide limited information. How are variations in kinematic patterns scaled to allow judgments of weight, a kinetic quantity? The possibility of a source of information for scaling in the kinematics is investigated. Judgments based only on patch-light displays are accurate to a degree that is improved by an extrinsic scaling basis. Finally, the sensitivity to scaling of alternative metrics used in judging is explored. Intrinsic metrics are discovered to be less sensitive to the absence of an extrinsic basis for scaling.     

Prehension movements in a patient (AC) with posterior parietal cortex damage and posterior callosal section

Prehension movements of the right hand were recorded in a right-handed man (AC), with an injury to the left posterior parietal cortex (PPC) and with a section of the left half of the splenium. The kinematic analysis of AC's grasping movements in direct and perturbed conditions was compared to that of five control subjects. A novel effect in prehension was revealed--a hemispace effect--in healthy controls only. Movements to the left hemispace were faster, longer, and with a smaller grasp aperture; perturbation of both object position and distance resulted in the attenuation of the direction effect on movement time and the time to velocity peak, with a reverse pattern in the time to maximum grip aperture. Nevertheless, the correlation between transport velocity amplitude and grasp aperture remained stable in both perturbed and non-perturbed movements, reflecting the coordination between reaching and grasping in control subjects. In contrast, transport and grasp, as well as their coordination in both direct and perturbed conditions, were negatively affected by the PPC and splenium lesion in AC, suggesting that transport and grasp rely on two functionally identifiable subsystems.     

Kinematic descriptions of upper limb function using simulated tasks in activities of daily living after stroke

Assessment of upper limb function poststroke is critical for clinical management and determining the efficacy of interventions. We designed a unilateral upper limb task to simulate activities of daily living to examine how chronic stroke survivors manage reaching, grasping and handling skills simultaneously to perform the functional task using kinematic analysis. The aim of the study was to compare the motor strategies for performing a functional task between paretic and nonparetic arms. Sixteen chronic stroke survivors were instructed to control an ergonomic spoon to transfer liquid from a large bowl to a small bowl using paretic or nonparetic arm. Kinematic data were recorded using a Vicon motion capture system. Outcome measures included movement duration, relative timing, path length, joint excursions, and trial-to-trial variability. Results showed that movement duration, spoon path length, and trunk path length increased significantly when participants used paretic arm to perform the task. Participants tended to reduce shoulder and elbow excursions, and increase trunk excursions to perform the task with paretic arm and altered the relative timing of the task. Although participants used different motor strategies to perform the task with their paretic arms, we did not find the significant differences in trial-to trial variability of joint excursions between paretic and nonparetic arms. The results revealed differences in temporal and spatial aspects of motor strategies between paretic and nonparetic arms. Clinicians should explore the underlying causes of pathological movement patterns and facilitate preferred movement patterns of paretic arm.     

Dynamic illusion effects in a reaching task: evidence for separate visual representations in the planning and control of reaching.

The effects of an orientation illusion on perception and 2 different actions were investigated. An 8-cm x 2-cm cylindrical bar was placed in front of participants at various orientations. A background grating was used to induce an orientation illusion. In a perception task, the illusion affected participants' ability to align the bar with their sagittal planes. In one reaching task, a similar effect of the illusion was found on the choice between 2 possible grasping postures. In a second reaching task involving a single grasping posture, the orientation illusion affected the orientation of the hand at the beginning of the reach but not near its end. The authors argue that reaching trajectories are planned and initiated through a context-dependent representation but are corrected on-line through a context-independent representation. The relation of this model to a more general dichotomy between perception and action is discussed.     

Spatial and temporal adaptations that accompany increasing catching performance during learning

The authors studied changes in performance and kinematics during the acquisition of a 1-handed catch. Participants were 8 women who took an intensive 2-week training program during which they evolved from poor catchers to subexpert catchers. An increased temporal consistency, shift in spatial location of ball-hand contact away from the body, and higher peak velocity of the transport of the hand toward the ball accompanied their improvement in catching performance. Moreover, novice catchers first adjusted spatial characteristics of the catch to the task constraints and fine-tuned temporal features only later during learning. A principal components analysis on a large set of kinematic variables indicated that a successful catch depends on (a) forward displacement of the hand and (b) the dynamics of the hand closure, thereby providing a kinematic underpinning for the traditional transport-manipulation dissociation in the grasping and catching literature.     

Anticipatory postural adjustments during a Fitts’ task: Comparing young versus older adults and the effects of different foci of attention

Anticipatory postural adjustments (APAs) are an integral part of standing balance. Previous research with balance control has shown that adopting an external focus of attention, compared to an internal focus of attention, yields better performance during motor skills. Despite the importance of APAs, especially among older adults, and the potential benefits of adopting an external focus of attention, studies investigating methods for improving APAs are limited. The aim of this study was to compare behavioral, kinematic and APAs measures while adopting different foci of attention among young and older adults when performing a lower extremity Fitts’ task. Ten young adults (mean age 24 years ± 4.37) and ten older adults (mean age 75 years ± 5.85) performed a lower-extremity reaching task (Fitts’ task) while adopting an external focus (focus on target) and an internal focus (focus on limb) in a within-subject design. A motion capture system was used to record participants’ movement data. Custom software derived movement time (MT), peak velocity (PV), time to peak velocity (ttPV) and variability at target (SD_T). Electromyography (EMG) was used to determine APAs onset and magnitude. The findings showed that an external focus of attention led to significantly shorter MT, higher PV, shorter ttPV and more accuracy when reaching the target (SD_T) for both age groups. Also, EMG results showed that, with an external focus, APAs onset occurred earlier and APAs magnitude was more efficient. As predicted by Fitts’ Law, participants spent more time executing movements to targets with higher indices of difficulty. Older adults compared to young adults were more adversely affected by the increase of difficulty of the Fitts’ task, specifically, on measures of APAs. In conclusion, adopting an external focus of attention led to better overall movement performance when performing a lower extremity Fitts’ task. The task used in the present study can distinguish between APAs for older and young adults. We recommend that future studies expand on our findings in order to establish a performance-based objective measure of APAs to assess clinical interventions for postural control impairment.     

Effects of Auditory Feedback on Movement Time in a Fitts Task

The purpose of the present experiment was to investigate the role of auditory feedback and its impact on movement time in a standard Fitts task. Feedback was given at the moment of target acquisition. A 2-way analysis of variance found significant differences between feedback groups at all three indexes of difficulty (F(2, 40) = 156.02, p < .001). Results from a mixed-model multivariate analysis of variance for kinematic factors show significant differences in peak velocity and the location of peak velocity when comparing feedback groups. In general, the addition of auditory feedback decreased the task ID by .5.