Visual control of reaching and grasping in infants

The Effect of START-Play Intervention on Reaching-Related Exploratory Behaviors in Children with Neuromotor Delays: A Secondary Analysis of a Randomized Controlled Trial

AIMS

Children with neuromotor delays are at risk for reaching and object exploration impairments, which may negatively affect their cognitive development and daily activity performance. This study evaluated the effectiveness of the Sitting Together And Reaching To Play (START-Play) intervention on reaching-related exploratory behaviors in children with neuromotor delays.

METHODS

In this randomized controlled clinical trial, 112 children (Mean = 10.80, SD = 2.59 months old at baseline) with motor delays were randomly assigned to receive START-Play intervention or usual care-early intervention. Performance for ten reaching-related exploratory behaviors was assessed at baseline and 1.5, 3, 6, 12 months post-baseline. Piecewise linear mixed-effects modeling was used to evaluate short- and long-term effects of the intervention.

RESULTS

Benefits of START-Play were observed for children with significant motor delays, but not for those with mild delays. START-Play was especially beneficial for children with significant motor delays who demonstrated early mastery in the reaching assessment (i.e., object contact ≥65% of the time within 3 months after baseline); these children showed greater improvements in manual, visual, and multimodal exploration, as well as intensity of exploration across time.

CONCLUSIONS

START-Play advanced the performance of reaching-related exploratory behaviors in children with significant motor delays.

From Hemispheric Asymmetry through Sensorimotor Experiences to Cognitive Outcomes in Children with Cerebral Palsy

Recent neuroimaging studies allowed us to explore abnormal brain structures and interhemispheric connectivity in children with cerebral palsy (CP). Behavioral researchers have long reported that children with CP exhibit suboptimal performance in different cognitive domains (e.g., receptive and expressive language skills, reading, mental imagery, spatial processing, subitizing, math, and executive functions). However, there has been very limited cross-domain research involving these two areas of scientific inquiry. To stimulate such research, this perspective paper proposes some possible neurological mechanisms involved in the cognitive delays and impairments in children with CP. Additionally, the paper examines the ways motor and sensorimotor experience during the development of these neural substrates could enable more optimal development for children with CP. Understanding these developmental mechanisms could guide more effective interventions to promote the development of both sensorimotor and cognitive skills in children with CP.

Effects of visual and visual-haptic perception of material rigidity on reaching and grasping in the course of development

The development of material property perception for grasping objects is not well explored during early childhood. Therefore, we investigated infants', 3-year-old children's, and adults' unimanual grasping behavior and reaching kinematics for objects of different rigidity using a 3D motion capture system. In Experiment 1, 11-month-old infants and for purposes of comparison adults, and in Experiment 2, 3-year old children were encouraged to lift relatively heavy objects with one of two handles differing in rigidity after visual (Condition 1) and visual-haptic exploration (Condition 2). Experiment 1 revealed that 11-months-olds, after visual object exploration, showed no significant material preference, and thus did not consider the material to facilitate grasping. After visual-haptic object exploration and when grasping the contralateral handles, infants showed an unexpected preference for the soft handles, which were harder to use to lift the object. In contrast, adults generally grasped the rigid handle exploiting their knowledge about efficient and functional grasping in both conditions. Reaching kinematics were barely affected by rigidity, but rather by condition and age. Experiment 2 revealed that 3-year-olds no longer exhibit a preference for grasping soft handles, but still no adult-like preference for rigid handles in both conditions. This suggests that material rigidity plays a minor role in infants' grasping behavior when only visual material information is available. Also, 3-year-olds seem to be on an intermediate level in the development from (1) preferring the pleasant sensation of a soft fabric, to (2) preferring the efficient rigid handle.

Assistive and Rehabilitative Effects of the Playskin LiftTM Exoskeletal Garment on Reaching and Object Exploration in Children With Arthrogryposis

IMPORTANCE

Children with arthrogryposis multiplex congenita are often delayed in their development of reaching and object exploration, which can place them at risk for associated delays in motor and cognitive development.

OBJECTIVE

To evaluate the longitudinal assistive and rehabilitative effects of the Playskin Lift™ (hereinafter Playskin), a novel exoskeletal garment, on reaching and object exploration abilities in children with arthrogryposis.

DESIGN

Single-case ABA design with a 1-mo baseline, 4-mo intervention, and 1-mo postintervention.

SETTING

Home environment.

PARTICIPANTS

Seventeen children with arthrogryposis (ages 6-35 mo at first visit; 5 boys).

INTERVENTION

Participants used the Playskin daily for 30 to 45 min while participating in structured intervention activities to encourage reaching for objects across play spaces larger than they were typically able to.

OUTCOMES AND MEASURES

Participants were tested biweekly throughout the study with and without the Playskin using a systematic reaching assessment. Coding of reaching and object exploration behavior was performed using OpenSHAPA software; statistical analyses were conducted using Hierarchical Linear and Nonlinear Modeling software. Feasibility of the Playskin for daily home intervention was evaluated with a parent perception questionnaire.

RESULTS

Positive assistive effects (improved performance when wearing the Playskin within sessions) and rehabilitative effects (improved independent performance after the Playskin intervention) were observed with increased active range of motion, expanded reaching space, improved grasping with the ventral side of the open hand, and greater complexity and multimodality and intensity of object exploration.

CONCLUSIONS AND RELEVANCE

The Playskin may be a feasible, effective assistive and rehabilitative device to advance object interaction and learning in young children with arthrogryposis.

WHAT THIS ARTICLE ADDS

The novel exoskeletal Playskin garment improves reaching and object exploration in young children with arthrogryposis.

A perspective on the development of hemispheric specialization, infant handedness, and cerebral palsy

Cerebral Palsy (CP), a common form of neurological pediatric disability, results from pre- or perinatal brain injury. Although there is growing evidence of the efficacy of motor learning-based therapies, several factors interact to produce variability in impairment and limit the effectiveness of these therapies. The variability of hand function present in children with CP indicates that a range of developmental pathways must contribute to the manifestation of individually unique characteristics of impairment. Despite two decades of progress using therapies derived from understanding the mechanisms controlling hand function, very little is known about the sensorimotor experiences occurring during development that likely shape later functional problems for children with CP. In this "perspective" paper, we propose that the study of the development of motor skills in typically developing infants may reveal experiential factors potentially important for creating remedial therapies for children with CP. Specifically, we use the development of infant handedness, a model of hemispheric specialization of function, as an example of how self-generated experiences and sensorimotor feedback can shape the development of limb control and hemispheric specialization. We illustrate how early sensorimotor asymmetries concatenate into pronounced differences in skill between the two hands. We suggest that this model of infant handedness provides a framework for studying the individual differences manifested in children with CP. These differences likely arise from aberrant sensorimotor experiences created by sensorimotor circuits disrupted by the early brain injury. We conclude that knowledge of the developmental events, including subtle motor behaviors, that shape sensorimotor pathways, can improve treatment options for children with CP.

Increasing task precision demands reveals that the reach and grasp remain subject to different perception-action constraints in 12-month-old human infants

The reach and grasp follow different developmental trajectories, but are often considered to have achieved nearly adult-like precision and integration by 12 months of age. This study used frame-by-frame video analysis to investigate whether increasing precision demands, by placing small reaching targets on a narrow pedestal rather than on a flat table, would influence the reach and grasp movements of 12-month-old infants in a complementary or differential fashion. The results reveal that placing the target atop a pedestal impaired the infants's ability to direct an appropriate digit towards the small target, but did not produce a corresponding decrease in the frequency with which they used an index-thumb pincer grip to grasp the target. This was due to the fact that, although infants were more likely to contact the target with a suboptimal part of the hand in the pedestal condition, a greater proportion of these suboptimal contacts ultimately transitioned to a successful index-thumb pincer grip. Thus, increasing task precision demands impaired reach accuracy, but facilitated index-thumb grip formation, in 12-month-old infants. The differential response of the reach and grasp to the increased precision demands of the pedestal condition suggests that the two movements are not fully integrated and, when precision demands are great, remain sensitive to different perception-action constraints in 12-month-old infants.

Play with objects in children with arthrogryposis: Effects of intervention with the Playskin Lift™ exoskeletal garment

Children with arthrogryposis multiplex congenita (AMC) often exhibit arm movement impairments that can negatively impact activities of daily living, such as reaching, object exploration, object play, and self-care. This study evaluated the effects of intervention involving the Playskin Lift™ (Playskin) exoskeletal garment on arm function during object play for children with AMC. Seventeen children with AMC (5 males; 6-35 months at the beginning of the study) were tested in their homes biweekly with and without the Playskin throughout a 1-month Baseline, 4-month Intervention, and 1-month Post-Intervention. Within sessions (assistive effects), children contacted and manipulated objects more while wearing the Playskin; they also showed greater intensity, complexity, and variability of behaviors performed during free play, as well as increased play space and reduced number of compensatory arm and trunk flings to facilitate reaching. Across time (rehabilitative effects), children significantly improved their visual-manual coupling as well as their ability to lift objects from a surface and to manipulate objects using one hand; in addition, children exhibited greater multimodality, variability, and intensity of their play behaviors. Current results suggest the Playskin Lift™ may serve as an effective assistive and rehabilitative device to improve play for children with arm movement impairments.

The Role of Sight of the Hand in the Development of Prehension in Childhood

In two studies, children between 5 and 10 years of age were asked to reach to grasp an object without sight of the hand during the movement. The oldest children and adults were faster when they could see the hand and increased maximum grip aperture when they could not see the hand. The 10-year-olds were less able to integrate grasp and lift than adults when they could see their hands. Children aged 5 and 6 showed no increase in movement time when they could not see the hand and did not adapt maximum grip aperture to lack of sight. These effects remained when children were encouraged to reach for and lift the target as quickly as possible. The results indicate that younger children did not give preference to vision in the control of prehension, while older children used visual feedback to improve efficiency. Dependence on sight of the hand for the control of prehension does not simply decrease with age, but it may be integrated into an anticipatory control strategy where it contributes to the efficiency of control.

Infants Born Preterm Demonstrate Impaired Exploration of Their Bodies and Surfaces Throughout the First 2 Years of Life

BACKGROUND

Non-object-oriented exploratory behaviors infants perform with their bodies and surfaces have been proposed to be key precursors of infants' object exploration, early learning, and future cognitive development. Little is known about the developmental trajectories of these behaviors, especially for infants born preterm.

OBJECTIVE

The purpose of the study was to longitudinally compare non-object-oriented exploratory behaviors performed by full-term and preterm infants.

DESIGN

The study followed 24 full-term and 30 preterm infants (6 with significant brain injury) performing non-object-oriented exploratory behaviors in prone, supine, and sitting from birth through 24 months.

METHODS

Infants were observed without objects or direct social interaction for 3 minutes in prone and supine (0 through 9 months) and in sitting (3 through 24 months). Behavioral coding produced data that were analyzed using hierarchical linear modeling. Developmental trajectories of behaviors were compared among full-term infants, preterm infants without significant brain injury, and preterm infants with significant brain injury.

RESULTS

Compared to full-term peers, preterm infants showed poorer postural control (less head lifting in prone), midline behavior (holding the head in midline, holding both hands in midline), hand-to-mouth and visual-motor behaviors against gravity, and more asymmetrical one-handed fisting. Preterm infants performed fewer bouts of non-object-oriented exploratory behaviors, and their behaviors were less variable with fewer combinations.

LIMITATIONS

There was a limited sample of infants born preterm with significant brain injury.

CONCLUSIONS

Non-object-oriented exploratory behaviors are important for early perceptual-motor development. Key differences were noted in these behaviors for infants born preterm. These differences may lead to impaired reaching, object exploration, and cognition. Early intervention programs should utilize assessments and interventions that target these very early non-object-oriented exploratory behaviors.

Concurrent anticipation of two object dimensions during grasping in 10-month-old infants: A quantitative analysis

The anticipation of more than one object dimension while grasping for objects has been rarely investigated in infancy. The few existing studies by Newell et al. and Schum et al. have revealed mixed results probably mainly due to methodological limitations. Therefore, the present experiments tested concurrent anticipatory grasping for two object dimensions, namely, object size and object orientation using a quantitative motion capture system (Vicon), in 10-month-old infants and adults. We presented objects varying in size (small vs. large) and orientation (horizontally vs. vertically) and analyzed participants' anticipatory hand configurations. As with adults, we observed that infants rotated their wrists, thumbs, and index fingers as a function of object orientation and adjusted their maximum grip apertures and their grip apertures shortly before they touched the objects as a function of object size. Analyses on an individual level showed that infants like adults anticipated both dimensions when the maximal values of aperture and angle were used but not when the measures shortly before touch were considered. Thus, the ability to anticipate more than one object dimension can already be observed at 10 months of age but seems to improve considerably over the first year of life.

Mapping the feel of the arm with the sight of the object: on the embodied origins of infant reaching

For decades, the emergence and progression of infant reaching was assumed to be largely under the control of vision. More recently, however, the guiding role of vision in the emergence of reaching has been downplayed. Studies found that young infants can reach in the dark without seeing their hand and that corrections in infants' initial hand trajectories are not the result of visual guidance of the hand, but rather the product of poor movement speed calibration to the goal. As a result, it has been proposed that learning to reach is an embodied process requiring infants to explore proprioceptively different movement solutions, before they can accurately map their actions onto the intended goal. Such an account, however, could still assume a preponderant (or prospective) role of vision, where the movement is being monitored with the scope of approximating a future goal-location defined visually. At reach onset, it is unknown if infants map their action onto their vision, vision onto their action, or both. To examine how infants learn to map the feel of their hand with the sight of the object, we tracked the object-directed looking behavior (via eye-tracking) of three infants followed weekly over an 11-week period throughout the transition to reaching. We also examined where they contacted the object. We find that with some objects, infants do not learn to align their reach to where they look, but rather learn to align their look to where they reach. We propose that the emergence of reaching is the product of a deeply embodied process, in which infants first learn how to direct their movement in space using proprioceptive and haptic feedback from self-produced movement contingencies with the environment. As they do so, they learn to map visual attention onto these bodily centered experiences, not the reverse. We suggest that this early visuo-motor mapping is critical for the formation of visually-elicited, prospective movement control.

Visibilidade dos braços afeta a preferência manual em bebês

Um aspecto de interesse sobre a formação da preferência manual humana em idades precoces é a extensão em que ela é afetada por informações aferentes. O objetivo deste estudo foi investigar o efeito da oclusão visual do braço preferido sobre a preferência manual e desempenho motor em bebês. Participaram cinco bebês com cinco meses de idade, que realizaram alcances com visão plena ou oclusão visual do braço preferido. O desempenho motor foi avaliado por meio de medidas cinemáticas. Os resultados indicaram que a oclusão visual induziu redução da frequência de alcances unimanuais com o braço ocluído durante e imediatamente após a oclusão visual. Oclusão visual não alterou o desempenho motor. Estes resultados indicam que a formação da preferência manual durante o desenvolvimento motor é afetada pela disponibilidade de informação visual dos braços, embora os bebês pareçam ter pouca capacidade de usar a visão para controle motor.

Visual information and object size in infant reaching

It has been suggested that the onset of successful reaching in infants is mediated by the onset of an ability to use sight of the hand to make corrective reaches. However, removing vision of the hand in infants younger than 6 months has not been shown to have an effect on reaching onset or kinematics. We investigated the use of vision of the hand by testing 6-, 9-, and 12-month-old infants reaching for objects in the light and in the dark. We found that infants reached faster in the dark at 6 months, and faster in the light at 1 year. Parallel effects were observed in the movement times. Consistent effects of altering target object size on average speed were seen at 12 months. The data support the hypothesis that vision is used by older infants around 6 months-of-age, and that reach and grasp planning differentiate with object size at about 9 and 12 months-of-age. At younger ages reaches are corrected on the basis of proprioceptive information and sight of the target object.

Development of Prehension Between 5 and 10 Years of Age: Distance Scaling, Grip Aperture, and Sight of the Hand

The authors investigated whether 5- to 10-year-old children (N = 75) differ from adults (N = 12) in the developmental course of distance scaling and the adaptations to the inability to see the hand during prehension movements. The children reached under a surface and grasped and lifted an object suspended through it. All children scaled velocity appropriately for movement distance, both with and without sight of the hand. However, 5- to 6-year-old children did not increase grip aperture with increased distance, whereas older children and adults did. The older children and adults spent longer after peak deceleration when they could not see the hand, and maximum grip aperture (MGA) was larger, providing an increased safety margin. Children aged 5 to 6 spent the same amount of time between peak deceleration and grasp, whether or not they could see the hand, and they failed to increase MGA when they could not see the hand. Prehension in the younger children differed from that of older children in two ways: The younger children did not integrate reach and grasp over different distances and did not use visual information about hand position to optimize accuracy.

Lessons From Infants: 1960-2000

Our image of the infant as an organism interacting with the environment has changed dramatically in the past 40 years. A new surge of infancy research began in the 1960s and continues unabated today. The view of the infant has been transformed from that of a primarily reflexive organism to a highly competent being, exquisitely sensitive to sensory and perceptual information. Controversy still swirls around the issue of when infants acquire specific knowledge about objects and events. New work is reviewed on how infants and toddlers use knowledge to guide their behavior in challenging situations. Despite the tremendous growth of knowledge about infant development over the past 40 years, it seems that we are on the threshold of even more exciting discoveries.