Feasibility of a home-based environmental enrichment paradigm to enhance purposeful activities in adults with traumatic brain injury: a case series

PURPOSE

To assess the feasibility, safety, and functional recovery of an Environmental Enrichment (EE) inspired paradigm for enhancing daily activities in people with traumatic brain injury.

METHODS

Two TBI-Caregiver dyads participated in the six-month study. A preinstalled harness provided the support structure that enabled the family to perform task-specific functional and cognitive goals. The pre- and post-intervention evaluations included the safety, feasibility, and clinical outcomes such as the 10-m walk test, the Timed Up and Go test, the Jebsen Hand Function test, the Six-Minute Walk test, and the Trail Making Test. The Actigraph GT9X recorded the Caregiver-TBI step count during days spent in harness and out of harness.

RESULTS

The study was feasible, safe, and both TBI subjects improved in functional outcomes. Analysis of Actigraph GT9X yielded mixed results.

CONCLUSION

A partnership with caregivers and adults with TBI to design an EE-focused community program could improve functional activities in real life. To optimize this intervention, caregivers will likely need an alternate approach to record time spent in the harness.IMPLICATIONS FOR REHABILITATIONThe complexities of the real world encourage meaningful activities and participation.Autonomy in everyday activities is an important long-term objective for adults with brain injury.Community-tailored harnesses designed to prevent falls encourages physical activity and social interaction.

GEARing smart environments for pediatric motor rehabilitation

BACKGROUND

There is a lack of early (infant) mobility rehabilitation approaches that incorporate natural and complex environments and have the potential to concurrently advance motor, cognitive, and social development. The Grounded Early Adaptive Rehabilitation (GEAR) system is a pediatric learning environment designed to provide motor interventions that are grounded in social theory and can be applied in early life. Within a perceptively complex and behaviorally natural setting, GEAR utilizes novel body-weight support technology and socially-assistive robots to both ease and encourage mobility in young children through play-based, child-robot interaction. This methodology article reports on the development and integration of the different system components and presents preliminary evidence on the feasibility of the system.

METHODS

GEAR consists of the physical and cyber components. The physical component includes the playground equipment to enrich the environment, an open-area body weight support (BWS) device to assist children by partially counter-acting gravity, two mobile robots to engage children into motor activity through social interaction, and a synchronized camera network to monitor the sessions. The cyber component consists of the interface to collect human movement and video data, the algorithms to identify the children's actions from the video stream, and the behavioral models for the child-robot interaction that suggest the most appropriate robot action in support of given motor training goals for the child. The feasibility of both components was assessed via preliminary testing. Three very young children (with and without Down syndrome) used the system in eight sessions within a 4-week period.

RESULTS

All subjects completed the 8-session protocol, participated in all tasks involving the selected objects of the enriched environment, used the BWS device and interacted with the robots in all eight sessions. Action classification algorithms to identify early child behaviors in a complex naturalistic setting were tested and validated using the video data. Decision making algorithms specific to the type of interactions seen in the GEAR system were developed to be used for robot automation.

CONCLUSIONS

Preliminary results from this study support the feasibility of both the physical and cyber components of the GEAR system and demonstrate its potential for use in future studies to assess the effects on the co-development of the motor, cognitive, and social systems of very young children with mobility challenges.

Exploratory analysis of a developmentally progressive modified ride-on car intervention for young children with Down syndrome

BACKGROUND

Children with Down syndrome (DS) may have limited opportunities to engage in self-directed mobility and play due to motor delays. A recent modified ride-on car innovation is the sit-to-stand (STS) model, which incorporates functional standing and walking training with the experience of powered mobility.

AIMS

This study aimed to: (1) describe total dosage and daily usage of three modified ride-on car modes (seated, standing, and power-push) by young children with DS; (2) examine the ability of young children with DS to independently activate the modified ride-on car in seated and standing modes; (3) describe the age of onset of selected motor milestones of the sample in comparison to DS norms.

MATERIALS AND METHODS

Eight young children with DS (8.6 ± 2.0 months) used three modes of the modified ride-on car over a 9-month intervention.

RESULTS

All eight children independently activated the modified ride-on car in seated and standing modes. Most motor milestones were achieved earlier in this sample than expected for DS norms, including the onset of independent walking.

CONCLUSIONS AND IMPLICATIONS

The developmentally progressive nature of the intervention and high dosage may have been instrumental in encouraging the onset of independent activation and earlier motor milestones.IMPLICATIONS FOR REHABILITATIONYoung children with Down syndrome were able to achieve independent activation in seated and standing modified ride-on cars.Developmentally progressive modified ride-on car interventions may facilitate motor skill development, but future work utilizing a randomized control group is needed to examine the potential motor developmental benefits of the STS model and power-push mode.The developmentally progressive nature of the intervention may have been instrumental in encouraging the onset of independent switch activation in both seated and standing modes, as well as the high dosage and adherence rates compared to previous studies.

Means-end problem solving in infancy: Development, emergence of intentionality, and transfer of knowledge

Behaviors and performance of 23 typically developing infants were assessed longitudinally at 6, 9, 12, 18, and 24 months in two means-end tasks: pulling a towel or rotating a turntable to obtain a supported object. With age, infants performed more goal-directed behaviors, leading to increased problem-solving success. Intentionality emerged earlier in the towel task than in the turntable task (6.9 vs. 10.8 months). Potential knowledge transfer between the tasks was first observed at 9 months. This study provides insight into the development of means-end learning, the emergence of intentionality, and potential transfer of knowledge in tasks involving a similar concept (support) but requiring different modes of action for success (pulling vs. rotating).

Prematurity may negatively impact means-end problem solving across the first two years of life

Preterm infants are at risk for delays in motor, perceptual, and cognitive development. While research has shown preterm infants may exhibit learning delays in the first months of life, these delays are commonly under-diagnosed. The purpose of this study was to longitudinally evaluate behavioral performance and learning in two means-end problem-solving tasks for 30 infants born preterm (PT) and 23 born full-term (FT). Infants were assessed at 6, 9, 12, 18, and 24 months-old in tasks that required towel pulling or turntable rotation to obtain a distant object. PT infants performed more non-goal-directed and less goal-directed behavior than FT infants throughout the study, resulting in a lower success rate among PT infants. PT infants showed delayed emergence of intentionality (prevalence of goal-directed behaviors) compared to FT infants in both tasks. Amount and variability of behavioral performance significantly correlated with task success differentially across age. The learning differences documented between PT and FT infants suggest means-end problem-solving tasks may be useful for the early detection of learning delays. The identification of behaviors associated with learning and success across age may be used to guide interventions aimed at advancing early learning for infants at risk.

Sitting Together And Reaching To Play (START-Play): Protocol for a Multisite Randomized Controlled Efficacy Trial on Intervention for Infants With Neuromotor Disorders

BACKGROUND

There is limited research examining the efficacy of early physical therapy on infants with neuromotor dysfunction. In addition, most early motor interventions have not been directly linked to learning, despite the clear association between motor activity and cognition during infancy.

OBJECTIVE

The aim of this project is to evaluate the efficacy of Sitting Together And Reaching To Play (START-Play), an intervention designed to target sitting, reaching, and motor-based problem solving to advance global development in infants with motor delays or neuromotor dysfunction.

DESIGN

This study is a longitudinal multisite randomized controlled trial. Infants in the START-Play group are compared to infants receiving usual care in early intervention (EI).

SETTING

The research takes place in homes in Pennsylvania, Delaware, Washington, and Virginia.

PARTICIPANTS

There will be 140 infants with neuromotor dysfunction participating, beginning between 7 to 16 months of age. Infants will have motor delays and emerging sitting skill.

INTERVENTION

START-Play provides individualized twice-weekly home intervention for 12 weeks with families to enhance cognition through sitting, reaching, and problem-solving activities for infants. Ten interventionists provide the intervention, with each child assigned 1 therapist.

MEASUREMENTS

The primary outcome measure is the Bayley III Scales of Infant Development. Secondary measures include change in the Early Problem Solving Indicator, change in the Gross Motor Function Measure, and change in the type and duration of toy contacts during reaching. Additional measures include sitting posture control and parent-child interaction.

LIMITATIONS

Limitations include variability in usual EI care and the lack of blinding for interventionists and families.

CONCLUSIONS

This study describes usual care in EI across 4 US regions and compares outcomes of the START-Play intervention to usual care.

Mobility in pictures: a participatory photovoice narrative study exploring powered mobility provision for children and families

AIM

Rehabilitation professionals are increasingly recognizing mobility as a basic human right and endorsing the efficacy of early powered mobility for children with mobility impairments to foster independence, promote socialization with peers and facilitate participation in family and community life. However, the relationship between mobility and technology provision, when considered in the context of lived experiences of children with mobility impairments and their families, is complex and understudied. Perceptions of these experiences from children's own points of view are especially limited, as is the use of participatory research methods in describing these experiences. The purpose of this study was to empower children and families as co-researchers, investigating their experiences and perspectives of powered mobility provision processes and early use of their mobility technology in their own words and images.  Methods: Two families in a major Midwest metropolitan area- one who was receiving a powered wheelchair and one who was receiving a modified powered ride-on toy car- participated as co-researchers from 2015-2016, documenting their experiences with a research camera and narrating their photos to describe meaningful or important aspects of their respective powered mobility provision processes and early use of their devices.

RESULTS

Four themes emerged: (1) Dys/Function of Mobility Technology; (2) Daily Life, Play and Participation; (3) Emerging Self/Advocacy and (4) Complex Family/Industry Interplay.  Conclusions: These themes and experiences may inform further innovation in powered mobility practices, generate new hypotheses about the role of technology in shaping disability identity and demonstrate the feasibility and impact of using participatory methods more broadly in rehabilitation research. Implications for Rehabilitation Participatory methods may be a useful and underutilized research tool in describing the impact of powered mobility provision processes on child and family experiences of technology and disability. Empowering children and families as co-researchers is important to move the field of powered mobility technology forward in creating innovative, accessible and socially welcoming devices and processes. It is important to capture the similarities and differences in child and family perceptions and experiences within different models of powered mobility provision, such as traditional powered wheelchair prescription and crowdsourced ride-on toy car modification. Powered mobility provision processes and the perceptions and experiences of children and families move beyond business or medical transactions and may help shape disability identity and pride. A disability studies framework may be useful in analyzing the complexities of technology provision and the nuanced interplay between bodies and technology.

Why We Move: Social Mobility Behaviors of Non-Disabled and Disabled Children across Childcare Contexts

BACKGROUND

Social mobility is defined as the co-occurrence of self-directed locomotion and direct peer interaction. Social mobility is a product of dynamic child-environment interactions and thus likely to vary across contexts (e.g., classroom, gymnasium, and playground).

PURPOSE

The purpose of this present study was to examine differences in children's social mobility: (1) across contexts by age and (2) between non-disabled and disabled children.

METHOD

Participants (n = 55 non-disabled and three disabled children; Mage = 3.1 years, SD = 1.4) were video recorded within a university-based early learning center. Children were recorded for 20 min in each context: classroom, gymnasium, and playground. A 15-s momentary time sampling method was used to code social mobility, the simultaneous occurrence of self-directed locomotion, and direct peer interaction. This variable was calculated as percent time within each context.

RESULTS

A planned Friedman's rank ANOVA (n = 55), stratified by age, indicated that older children (3-5 years old) differed across contexts in their social mobility [χ2(2) ~ 7.3-10.5, p < 0.025], whereas younger children (1-2 years old) were similar across contexts. Social mobility was significantly lower in the classroom compared with the playground and gymnasium (with no difference between the latter contexts) for older children. Visual analysis confirmed that disabled children (n = 3) engaged in substantially less time in social mobility (average 0-1%), compared with non-disabled, age-similar peers (2-3 years old average 1-12%) across all contexts.

CONCLUSION

A substantial gap exists between non-disabled and disabled children for social mobility. There is an increase in magnitude and variability of social mobility around age three that suggests the gap between non-disabled and disabled children will continue to widen.

Infant born preterm have delayed development of adaptive postural control in the first 5 months of life

Infants born preterm are at increased risk of developmental disabilities, that may be attributed to their early experiences and ability to learn. The purpose of this paper was to evaluate the ability of infants born preterm to adapt their postural control to changing task demands.

METHODS

This study included 18 infants born at 32 weeks of gestation or less whose posture was compared in supine under 2 conditions, with and without a visual stimulus presented. The postural variability, measured with root mean squared displacement of the center of pressure, and postural complexity, measured with the approximate entropy of the center of pressure displacement were measured longitudinally from 2.5 to 5 months of age.

RESULTS AND DISCUSSION

The infants looked at the toys in midline for several months prior to adapting their postural variability in a manner similar to full term infants. Only after postural variability was reduced in both the caudal cephalic and medial lateral direction in the toy condition did the infants learn to reach for the toy. Postural complexity did not vary between conditions. These findings suggest that infants used a variety of strategies to control their posture. In contrast to research with infants born full term, the infants born preterm in this study did not identify the successful strategy of reducing movement of the center of pressure until months after showing interest in the toy. This delayed adaptation may impact the infants ability to learn over time.

Playskin Lift: Development and Initial Testing of an Exoskeletal Garment to Assist Upper Extremity Mobility and Function

BACKGROUND

A person's ability to move his or her arms against gravity is important for independent performance of critical activities of daily living and for exploration that facilitates early cognitive, language, social, and perceptual-motor development. Children with a variety of diagnoses have difficulty moving their arms against gravity.

OBJECTIVE

The purpose of this technical report is to detail the design process and initial testing of a novel exoskeletal garment, the Playskin Lift, that assists and encourages children to lift their arms against gravity.

DESIGN

This report details the design theory and process, the device, and the results of field testing with a toddler with impaired upper extremity function due to arthrogryposis multiplex congenita.

RESULTS

The Playskin Lift is an inexpensive (<$30 material costs), easy to use (5/5 rating), comfortable (5/5 rating), and attractive (4/5 rating) device. While wearing the device, the child was able to contact objects more often throughout an increased play space, to look at toys more while contacting them, and to perform more complex interactions with toys.

LIMITATIONS

This report details initial testing with one child. Future testing with more participants is recommended.

CONCLUSIONS

These results suggest that by considering the broad needs of users, including cost, accessibility, comfort, aesthetics, and function, we can design inexpensive devices that families and clinicians can potentially fabricate in their own communities to improve function, participation, exploration, and learning for children with disabilities.

Not just playing around: infants' behaviors with objects reflect ability, constraints, and object properties

This study describes infants' behaviors with objects in relation to age, body position, and object properties. Object behaviors were assessed longitudinally in 22 healthy infants supine, prone, and sitting from birth through 2 years. Results reveal: (1) infants learn to become intense and sophisticated explorers within the first 6 months of life; (2) young infants dynamically and rapidly shift among a variety of behavioral combinations to gather information; (3) behaviors on objects develop along different trajectories so that behavioral profiles vary across time; (4) object behaviors are generally similar in supine and sitting but diminished in prone; and (5) infants begin matching certain behaviors to object properties as newborns. These data demonstrate how infants learn to match their emerging behaviors with changing positional constraints and object affordances.

Design of a robotic mobility system with a modular haptic feedback approach to promote socialization in children

Self-initiated mobility is a causal factor in children's development. Previous studies have demonstrated the effectiveness of our training methods in learning directional driving and navigation. The ultimate goal of mobility training is to enable children to be social, that is, to interact with their peers. A powered mobility device was developed that can localize itself, map the environment, plan an obstacle-free path to a goal, and ensure safety of a human driver. Combined with a positioning system, this system is able to apply a force field using a modular haptic feedback approach to train subjects to drive towards an object, a caregiver, a peer, or a group of peers. System feasibility was tested by designing a 'ball chasing' game. Results show that the system is promising in promoting socialization in children.

Postural complexity differs between infant born full term and preterm during the development of early behaviors

BACKGROUND AND AIMS

Postural control differs between infants born preterm and full term at 1-3weeks of age. It is unclear if differences persist or alter the development of early behaviors. The aim of this longitudinal study was to compare changes in postural control variability during development of head control and reaching in infants born preterm and full term.

METHODS

Eighteen infants born preterm (mean gestational age 28.3±3.1weeks) were included in this study and compared to existing data from 22 infants born full term. Postural variability was assessed longitudinally using root mean squared displacement and approximate entropy of the center of pressure displacement from birth to 6months as measures of the magnitude of the variability and complexity of postural control. Behavioral coding was used to quantify development of head control and reaching.

RESULTS

Group differences were identified in postural complexity during the development of head control and reaching. Infants born preterm used more repetitive and less adaptive postural control strategies than infants born full term. Both groups changed their postural complexity utilized during the development of head control and reaching.

DISCUSSION

Early postural complexity was decreased in infants born preterm, compared to infants born full term. Commonly used clinical assessments did not identify these early differences in postural control. Altered postural control in infants born preterm influenced ongoing skill development in the first six months of life.

Instability of delay classification and determination of early intervention eligibility in the first two years of life

The purpose of this study was to determine the effectiveness of the Bayley Scales of Infant Development, Third Edition (Bayley-III) to track development and classify delays in low- and high-risk infants across the first two years of life. We assessed cognitive, language, and motor development in 24 low-risk full-term and 30 high-risk preterm infants via seven assessments performed between 3 and 24 months corrected age. The Bayley-III resulted in highly unstable delay classifications, low sensitivities, and poor positive predictive values across time. The results highlight that early intervention professionals, researchers, and policy makers should: (1) emphasize clinical opinion and prevalence of risk factors rather than standardized assessment findings when classifying delays and determining eligibility for services, and (2) develop more effective developmental assessments for infants and young children.

Design of a robotic mobility system to promote socialization in children

Self-initiated mobility is a causal factor in children's development. Previous studies have demonstrated the effectiveness of our training methods in learning directional driving and navigation. The ultimate goal of mobility training is to enable children to be social, that is, to interact with peers. A powered mobility device was developed that can localize itself, map the environment, plan an obstacle-free path to a goal, and ensure safety of a human driver. Combined with a positioning system, this system is able to apply a force field to train subjects to drive towards an object, a caregiver, a peer, or a group of peers. System feasibility was tested by designing a 'ball chasing' game. Results show that the system is promising in promoting socialization in children.

Assessment and stability of early learning abilities in preterm and full-term infants across the first two years of life

Infants born preterm have increased risk for learning disabilities yet we lack assessments to successfully detect these disabilities in early life. We followed 23 full-term and 29 preterm infants from birth through 24 months to assess for differences in and stability of learning abilities across time. Measures included the Bayley-III cognitive subscale, the mobile paradigm assessment, and a means-end learning assessment. Preterm infants had poorer performance on measures of cognition and learning across the first two years of life. Learning performance at 3-4 months was consistent with learning performance at 12-24 months of age. At 3-4 months, the mobile paradigm had better sensitivity and predictive values for predicting 24-month cognitive delays on the Bayley-III than did the Bayley-III itself. At 12-18 months, the means-end learning assessment had better sensitivity than the Bayley-III for identifying 24-month cognitive delays on the Bayley-III. The results suggest that: (1) infants born preterm may demonstrate learning differences as early as the first few months of life, (2) learning differences identified in the first months of life are likely to persist throughout the second year of life, and (3) learning assessments that measure how infants and toddlers use their typical behaviors to problem-solve to control external events may be more effective than traditional standardized assessment tools for detecting early learning delays.

The onset of reaching significantly impacts how infants explore both objects and their bodies

The purpose of this study was to describe how reaching onset affects the way infants explore objects and their own bodies. We followed typically developing infants longitudinally from 2 through 5 months of age. At each visit we coded the behaviors infants performed with their hand when an object was attached to it versus when the hand was bare. We found increases in the performance of most exploratory behaviors after the emergence of reaching. These increases occurred both with objects and with bare hands. However, when interacting with objects, infants performed the same behaviors they performed on their bare hands but they performed them more often and in unique combinations. The results support the tenets that: (1) the development of object exploration begins in the first months of life as infants learn to selectively perform exploratory behaviors on their bodies and objects, (2) the onset of reaching is accompanied by significant increases in exploration of both objects and one's own body, (3) infants adapt their self-exploratory behaviors by amplifying their performance and combining them in unique ways to interact with objects.

Relation between early motor delay and later communication delay in infants at risk for autism

BACKGROUND

Motor delays have been reported in retrospective studies of young infants who later develop Autism Spectrum Disorders (ASDs).

OBJECTIVE

In this study, we prospectively compared the gross motor development of a cohort at risk for ASDs; infant siblings of children with ASDs (AU sibs) to low risk typically developing (LR) infants.

METHODS

24 AU sibs and 24 LR infants were observed at 3 and 6 months using a standardized motor measure, the Alberta Infant Motor Scale (AIMS). In addition, as part of a larger study, the AU sibs also received a follow-up assessment to determine motor and communication performance at 18 months using the Mullen Scales of Early Learning.

RESULTS

Significantly more AU sibs showed motor delays at 3 and 6 months than LR infants. The majority of the AU sibs showed both early motor delays and later communication delays.

LIMITATIONS

Small sample size and limited follow-up.

CONCLUSIONS

Early motor delays are more common in AU sibs than LR infants. Communication delays later emerged in 67-73% of the AU sibs who had presented with early motor delays. Overall, early motor delays may be predictive of future communication delays in children at risk for autism.

Early complexity supports development of motor behaviors in the first months of life

Complexity in motor behavior is a hallmark of healthy systems. The purpose of this study was to investigate postural complexity during development of early motor behaviors and under two conditions. Twenty-two infants participated from 1 to 6 months of age. Linear and nonlinear measures of displacement of the center of pressure at the base of support were used to quantify magnitude and temporal structure of postural control. Behavioral coding was used to quantify the emergence of midline head control and early reaching. Results suggest that infants have complexity in postural control strategies early in development. This complexity decreases as infants learn motor behaviors, even when magnitude of the postural variability does not change. Infants were able to adapt the magnitude of postural control variability under different conditions. We propose that infants proceed through three stages which support the infant's ability to adapt motor behaviors.

Design of a novel mobility device controlled by the feet motion of a standing child

Self-generated mobility is a major contributor to the physical, emotional, cognitive, and social development of infants and toddlers. When young children have disorders that hinder self locomotion, their development is at risk for delay. Independent mobility via traditional power mobility devices may prevent this delay, but do little to encourage the child's development of gross motor skills. This research aims to develop a bio-driven mobile-assistive device that is controlled and driven by moving the feet, which may encourage the development of gross motor skills. In this study, system feasibility is shown by experiments on five typically developing toddlers and one special needs toddler with spastic cerebral palsy. Children were placed in the bio-driven device and instructed to navigate through a maze. All subjects were able to successfully complete the maze in multiple trials. Additionally, two toddlers showed evidence of improved driving skill by completing the maze in shorter times in successive trials on a given testing day. The results suggest that such a device is feasible for purposeful driving. Recommendations are given for the device and protocol redesign for related future testing.

Training Toddlers Seated on Mobile Robots to Steer Using Force-Feedback Joystick

The broader goal of our research is to train infants with special needs to safely and purposefully drive a mobile robot to explore the environment. The hypothesis is that these impaired infants will benefit from mobility in their early years and attain childhood milestones, similar to their healthy peers. In this paper, we present an algorithm and training method using a force-feedback joystick with an "assist-as-needed" paradigm for driving training. In this "assist-as-needed" approach, if the child steers the joystick outside a force tunnel centered on the desired direction, the driver experiences a bias force on the hand. We show results with a group study on typically developing toddlers that such a haptic guidance algorithm is superior to training with a conventional joystick. We also provide a case study on two special needs children, under three years old, who learn to make sharp turns during driving, when trained over a five-day period with the force-feedback joystick using the algorithm.

Design of a novel mobility device controlled by the feet motion of a standing child: a feasibility study

Self-generated mobility is a major contributor to the physical, emotional, cognitive, and social development of infants and toddlers. When young children have disorders that hinder self locomotion, their development is at risk for delay. Independent mobility via traditional power mobility devices may prevent this delay, but do little to encourage the child's development of gross motor skills. This research aims to develop a bio-driven mobile-assistive device that is controlled and driven by moving the feet, which may encourage the development of gross motor skills. In this study, system feasibility is shown by experiments on five typically developing toddlers and one special needs toddler with spastic cerebral palsy. Children were placed in the bio-driven device and instructed to navigate through a maze. All subjects were able to successfully complete the maze in multiple trials. In addition, two toddlers showed evidence of improved driving skill by completing the maze in shorter times in successive trials on a given testing day. The results suggest that such a device is feasible for purposeful driving. Recommendations are given for the device and protocol redesign for related future testing.

Design of a Novel Mobility Interface for Infants on a Mobile Robot by Kicking

Many infants with special needs, such as with Down syndrome, cerebral palsy, and autism have delayed independent mobility due to weak musculature and/or poor coordination. Children with mobility impairments often do not use powered chairs until the age of five, as per current medical practice. Consequently, these children spend considerably less time moving independently around in their environment compared with typically developing children of the same age. Lack of independent mobility may result in delays in their cognitive, perceptual, social, and emotional development, which are well correlated with locomotion. This paper describes a novel mobility interface for the robot to explore the environment when infants are placed in a prone position. Infants can maneuver the robot through a drive interface that utilizes a camera to detect the motion of markers attached to their legs. We expect that infants will learn to drive the device by swinging their legs. Specifically, this paper demonstrates feasibility of this drive interface using data from two infants. Future studies will determine how infants can be trained to drive a robot purposefully and how such self-generated locomotion affects their long-term development.

The organization of intralimb and interlimb synergies in response to different joint dynamics

We sought to understand differences in joint coordination between the dominant and nondominant arms when performing repetitive tasks. The uncontrolled manifold approach was used to decompose the variability of joint motions into components that reflect the use of motor redundancy or movement error. First, we hypothesized that coordination of the dominant arm would demonstrate greater use of motor redundancy to compensate for interaction forces than would coordination of the nondominant arm. Secondly, we hypothesized that when interjoint dynamics were more complex, control of the interlimb relationship would remain stable despite differences in control of individual hand paths. Healthy adults performed bimanual tracing of two orientations of ellipses that resulted in different magnitudes of elbow interaction forces. For the dominant arm, joint variance leading to hand path error was the same for both ellipsis orientations, whereas joint variance reflecting the use of motor redundancy increased when interaction moment was highest. For the nondominant arm, more joint error variance was found when interaction moment was highest, whereas motor redundancy did not differ across orientations. There was no apparent difference in interjoint dynamics between the two arms. Thus, greater skill exhibited by the dominant arm may be related to its ability to utilize motor redundancy to compensate for the effect of interaction forces. However, despite the greater error associated with control of the nondominant hand, control of the interlimb relationship remained stable when the interaction moment increased. This suggests separate levels of control for inter- versus intra-limb coordination in this bimanual task.

No stable arm preference during the pre-reaching period: a comparison of right and left hand kinematics with and without a toy present

Adult hand preference emerges from complex developmental changes in arm and hand use during childhood. Recent reports have highlighted the importance of understanding arm and hand use during the first year of life including the period before reach onset. This longitudinal study tested the hypothesis that significant right-left differences exist in pre-reaching arm movements. We examined right and left hand kinematics from 13 healthy infants during trials with and without a toy present from 8 weeks of age through the week of reach onset. Significant right-left differences were found, however there was no clear pattern within a condition or across conditions. Without a toy present, the right hand moved faster, yet ended further from midline, and displayed more movements during the Late phase compared to other phases. With a toy present, the right hand moved longer lengths, yet ended movements further away from the toy. When left and right hand kinematics were combined, previous findings of right hand kinematics alone were supported. Although infants begin adapting their pre-reaching kinematics many weeks before reach onset, we did not find evidence of a systematic right--left difference before reach onset in movements with or without a toy present. Our results, coupled with other reports, suggest hand asymmetries begin to emerge over the year following reach onset amid developmental changes both within the infant, and the physical and social environment.

Toy-oriented changes during early arm movements IV: shoulder-elbow coordination

Our recent work on the initial emergence of reaching identified a mosaic of developmental changes and consistencies within the hand and joint kinematics of arm movements across the pre-reaching period. The purpose of this study was to test hypotheses regarding the coordination of hand and joint kinematics over this same pre-reaching period. Principal component analysis (PCA) was conducted on hand, shoulder, and elbow kinematic data from 15 full-term infants observed biweekly from 8 weeks of age through the week of reach onset. Separate PCAs were calculated for spatial variables and for velocity variables in trials with a toy and without a toy. From the PCA results, we constructed 'variance profiles' to reflect the coordinative structure of the hand, shoulder, and elbow. By coordinative structure is meant here the relative contribution of each joint to the factors revealed by the PCA. Shifts in these profiles, which reflected coordination changes, were compared across the hand and joints within each pre-reaching phase (Early, Mid, Late) as well as across phases and trial conditions (no-toy and toy). Results identified both surprising consistencies and important developmental changes in coordination. First, over development, spatial coordination changed in different ways for the shoulder and elbow. Between the Early and Late phases, spatial coordination at the shoulder showed more adult-like coordination during both spontaneous movements and movements with a toy present. In contrast, elbow spatial coordination became more adult-like only during movements with a toy and less adult-like during spontaneous movements. Second, over development, velocity coordination became more adult-like at both joints in movements with and without a toy present. We propose that the features of coordination that changed over development suggest explanations for the differential roles and developmental trajectories of the control of arm movements between the shoulder and elbow. We propose that features that remained consistent over development suggest the presence of developmentally important constraints inherent in arm biomechanics, which may simplify arm control for reaching. Taken together, these findings highlight the critical role of spontaneous arm movements in the emergence of purposeful reaching.

Toy-oriented changes in early arm movements III: constraints on joint kinematics

The purpose of this study was to identify invariant features of shoulder and elbow kinematics during prereaching arm movements with and without a toy present. Invariant movement features may reflect the presence of constraints that reduce the complexity of learning to reach and provide a link between early arm movements and reaching. Joint excursion and smoothness were consistently greater at the shoulder than the elbow suggesting strong organismal constraints on prereaching movements. Speed became greater in the shoulder than the elbow only with a toy present during the 4 weeks leading up to reach onset suggesting the introduction of task related constraints. We propose that organismal constraints on joint coordination throughout the prereaching period provide a foundation for the overlay of task related constraints closer to reach onset. We also suggest that the coordinative structures of early arm movements and later reaching may be much more similar than currently thought. This similarity would significantly reduce the elements needing to be actively controlled, and simplify the learning process.

Toy-oriented changes in early arm movements II--joint kinematics

Our recent work suggests that infants begin to change their hand and joint kinematics in the presence of a toy months before the onset of purposeful reaching. Moreover, these 'toy-oriented' changes in hand kinematics cluster into Early, Mid and Late phases. The purpose of the present study was to test hypotheses regarding toy-oriented changes in joint kinematics in the same infants.

METHODS

Thirteen infants were observed every other week from 8 weeks up to the first week of reaching around 20 weeks. At each session, a high-speed motion analysis system recorded infants' arm movements with and without a toy present.

RESULTS

During the Early phase, infants scaled down their movements. In contrast, during the Mid phase infants scaled up their movements and did not change the relationship between the shoulder and elbow for speed and smoothness-related variables. In addition, infants showed toy-oriented changes such as increase in shoulder flexion and adduction. In the Late phase, infants continued to produce toy-oriented changes in shoulder orientation, and increased shoulder excursion and speed relative to the elbow. Thus, the toy-oriented changes in hand kinematics in the Mid and Late phases [Bhat, A. N., & Galloway, J. C. (2006). Toy-oriented changes in early arm movements of young infants: Hand kinematics. Infant Behavior and Development, 29(3), 358-372] more closely followed changes in shoulder kinematics. Lastly, results are discussed in terms of shoulder-elbow dissociations, speed-amplitude relationships, and the key role of spontaneous movements in the development of reaching.

Toy-oriented changes during early arm movements: hand kinematics

In a recent cross-sectional study, we found that young infants changed their spontaneous arm movements in the presence of a toy, termed 'toy-oriented changes', in systematic ways beginning many weeks before their first consistent reaches [Bhat, A. N., Heathcock, J. H., & Galloway, J. C. (2005). Toy-oriented changes in hand and joint kinematics during the emergence of purposeful reaching. Infant Behavior and Development, 28(4), 445-465]. The purpose of the present study was to test specific hypotheses regarding toy-oriented changes in a longitudinal design.

METHODS

Thirteen infants were observed every other week from 8 weeks of age up to the onset of reaching. At each session, hand and joint motions were observed with and without a toy present using a high-speed motion capture system. This paper focuses on the toy-oriented changes in hand variables.

RESULTS

As predicted, infants displayed a meaningful pattern of toy-oriented changes, which systematically changed as infants approached the first week of reaching. During the Early phase (8-10 weeks before reaching), infants scaled down their movement length and speed in the presence of a toy. During the Mid phase (4-6 weeks before reaching), infants scaled up movement number and speed, increased movement smoothness, and decreased their hand-toy distance in the presence of a toy. During the Late phase (within 2 weeks of reaching), infants continued to change their hand's position to get closer to the toy and began contacting it. Interestingly, movement number and smoothness displayed similar developmental patterns, where movement length and speed displayed similar patterns.

CONCLUSION

Toy-oriented adaptation of arm movements emerges in the first months of life and forms a complex, yet tractable continuum with purposeful reaching. These results provide a foundation to test more specific hypotheses of hand and joint coordination in both typically developing infants and those infants born at risk for coordination impairments.

Novel muscle patterns for reaching after cervical spinal cord injury: a case for motor redundancy

A fundamental issue in the neuromotor control of arm movements is whether the nervous system can use distinctly different muscle activity patterns to obtain similar kinematic outcomes. Although computer simulations have demonstrated several possible mechanical and torque solutions, there is little empirical evidence that the nervous system actually employs fundamentally different muscle patterns for the same movement, such as activating a muscle one time and not the next, or switching from a flexor to an extensor. Under typical conditions, subjects choose the same muscles for any given movement, which suggests that in order to see the capacity of the nervous system to make a different choice of muscles, the nervous system must be pushed beyond the normal circumstances. The purpose of this study, then, was to examine an atypical condition, reaching of cervical spinal cord injured (SCI) subjects who have a reduced repertoire of available distal arm muscles but otherwise a normal nervous system above the level of lesion. Electromyography and kinematics of the shoulder and elbow were examined in the SCI subjects performing a center-out task and then compared to neurologically normal control subjects. The findings showed that the SCI-injured subjects produced reaches with typical global kinematic features, such as straight finger paths, bell-shaped velocities, and joint excursions similar to control subjects. The SCI subjects, however, activated only the shoulder agonist muscle for all directions, unlike the control pattern that involved a reciprocal pattern at each joint (shoulder, elbow, and wrist). Nonetheless, the SCI subjects could activate their shoulder antagonist muscles, elbow flexors, and wrist extensor (extensor carpi radialis) for isometric tasks, but did not activate them during the reaching movements. These results demonstrate that for reaching movements, the SCI subjects used a strikingly different pattern of intact muscle activities than control subjects. Hence, the findings imply that the nervous system is capable of choosing either the control pattern or the SCI pattern. We would speculate that control subjects do not select the SCI pattern because the different choice of muscles results in kinematic features (reduced fingertip speed, multiple shoulder accelerations) other than the global features that are somehow less advantageous or efficient.

The relative kicking frequency of infants born full-term and preterm during learning and short-term and long-term memory periods of the mobile paradigm

BACKGROUND AND PURPOSE

Infants born preterm differ in their spontaneous kicking, as well as their learning and memory abilities in the mobile paradigm, compared with infants born full-term. In the mobile paradigm, a supine infant's ankle is tethered to a mobile so that leg kicks cause a proportional amount of mobile movement. The purpose of this study was to investigate the relative kicking frequency of the tethered (right) and nontethered (left) legs in these 2 groups of infants.

SUBJECTS

Ten infants born full-term and 10 infants born preterm (<33 weeks gestational age, <2,500 g) and 10 comparison infants participated in the study.

METHODS

The relative kicking frequencies of the tethered and nontethered legs were analyzed during learning and short-term and long-term memory periods of the mobile paradigm.

RESULTS

Infants born full-term showed an increase in the relative kicking frequency of the tethered leg during the learning period and the short-term memory period but not for the long-term memory period. Infants born preterm did not show a change in kicking pattern for learning or memory periods, and consistently kicked both legs in relatively equal amounts.

DISCUSSION AND CONCLUSION

Infants born full-term adapted their baseline kicking frequencies in a task-specific manner to move the mobile and then retained this adaptation for the short-term memory period. In contrast, infants born preterm showed no adaptation, suggesting a lack of purposeful leg control. This lack of control may reflect a general decrease in the ability of infants born preterm to use their limb movements to interact with their environment. As such, the mobile paradigm may be clinically useful in the early assessment and intervention of infants born preterm and at risk for future impairment.

General and Task-Related Experiences Affect Early Object Interaction

The effects of 2 weeks of no, general, and task-related enhanced movement experiences on 8- to 12-week-old infants' (N = 30) hand and foot interactions with objects were assessed using standard video and motion analysis. For hand-object interaction ability, general and task experience led to greater success than did no experience, and task experience led to greater success than did general experience. Only general experience led to greater success for foot-object interaction ability. Experiences therefore resulted in differential effects depending on which limbs infants used. The results suggest that different movement experiences can advance infants' earliest object interactions. They also indicate that even early purposeful behaviors result from a complex interplay of experience, current ability, and task demands.

Shoulder and elbow joint power differ as a general feature of vertical arm movements

Consistent patterns of joint power underlie coordinated lower extremity behaviors such as running and walking. Recent work found that shoulder and elbow power consistently differed during reaching movements in the horizontal plane. Moreover, joint power during horizontal reaching appears correlated with motor cortical activity. It is not known if the feature of differential joint power extends to vertical plane reaches or to reaches of different movement conditions. The purpose of this study was to test for differential shoulder and elbow power during the acceleratory and deceleratory phases of fast and normal speed vertical reaches in sitting and supine positions. Our results suggest that shoulder and elbow power typically differed both within and across conditions. First, shoulder power values were positive or negative dependent largely on movement direction and movement phase. That is, for each direction and phase, the shoulder either generated or absorbed energy independent of speed or body position. Second, and unexpectedly, reaches of certain condition combinations had similar shoulder power magnitudes across directions. In contrast, elbow power values for each direction varied between positive and negative values depending on phase, speed and position, and no two condition combinations overlapped across directions. Third, as target direction, movement phase and body position varied, shoulder power at fast and normal speeds were linearly correlated, as was shoulder power in sitting and in supine. In contrast, elbow power was linearly correlated only between speeds. These results join other studies to suggest that the neuromotor control of the shoulder may be less complex as compared to the elbow as a general feature of reaching movements. This differential control has important implications for the study of reaching impairments in neurorehabilitation populations, and provides a potentially important variable in the study of cortical firing patterns.

General coordination of shoulder, elbow and wrist dynamics during multijoint arm movements

Studies of multijoint arm movements have demonstrated that the nervous system anticipates and plans for the mechanical effects that arise from motion of the linked limb segments. The general rules by which the nervous system selects appropriate muscle activities and torques to best deal with these intersegmental effects are largely unknown. In order to reveal possible rules, this study examined the relationship of muscle and interaction torques to joint acceleration at the shoulder, elbow and wrist during point-to-point arm movements to a range of targets in the horizontal plane. Results showed that, in general, dynamics differed between the joints. For most movements, shoulder muscle torque primarily determined net torque and joint acceleration, while interaction torque was minimal. In contrast, elbow and wrist net torque were determined by a combination of muscle and interaction torque that varied systematically with target direction and joint excursion. This "shoulder-centered pattern" occurred whether subjects reached targets using straight or curved finger paths. The prevalence of a shoulder-centered pattern extends findings from a range of arm movement studies including movement of healthy adults, neurological patients, and simulations with altered interaction effects. The shoulder-centered pattern occurred for most but not all movements. The majority of the remaining movements displayed an "elbow-centered pattern," in which muscle torque determined initial acceleration at the elbow and not at the shoulder. This occurred for movements when shoulder excursion was <50% of elbow excursion. Thus, both shoulder- and elbow-centered movements displayed a difference between joints but with reversed dynamics. Overall, these findings suggest that a difference in dynamics between joints is a general feature of horizontal plane arm movements, and this difference is most commonly reflected in a shoulder-centered pattern. This feature fits well with other general shoulder-elbow differences suggested in the literature on arm movements, namely that: (a) agonist muscle activity appears more closely related to certain joint kinematics at the shoulder than at the elbow, (b) adults with neurological damage display less disruption of shoulder motion than elbow motion, and (c) infants display adult-like motion first in the shoulder and last at the wrist.

Control of the wrist in three-joint arm movements to multiple directions in the horizontal plane

In a reaching movement, the wrist joint is subject to inertial effects from proximal joint motion. However, precise control of the wrist is important for reaching accuracy. Studies of three-joint arm movements report that the wrist joint moves little during point-to-point reaches, but muscle activities and kinetics have not yet been described across a range of movement directions. We hypothesized that to minimize wrist motion, muscle torques at the wrist must perfectly counteract inertial effects arising from proximal joint motion. Subjects were given no instructions regarding joint movement and were observed to keep the wrist nearly motionless during center-out reaches to directions throughout the horizontal plane. Consistent with this, wrist muscle torques exactly mirrored interaction torques, in contrast to muscle torques at proximal joints. These findings suggest that in this reaching task the nervous system chooses to minimize wrist motion by anticipating dynamic inertial effects. The wrist muscle torques were associated with a direction-dependent choice of muscles, also characterized by initial reciprocal activation rather than initial coactivation to stiffen the wrist joint. In a second experiment, the same pattern of muscle activities persisted even after many trials reaching with the wrist joint immobilized. These results, combined with similar features at the three joints, such as cosine-like tuning of muscle torques and of muscle onsets across direction, suggest that the nervous system uses similar rules for muscles at each joint, as part of one plan for the arm during a point-to-point reach.