Goal directed reaching and postural control in supine position in healthy infants

Reaching While Learning to Sit: Capturing the Kinematics of Co-Developing Skills at Home

This study examined the co-development of infant reaching and postural control across the transition to arms-free sitting at home. We observed infants with typical likelihood (TL; n = 24) and elevated likelihood (EL; n = 20) for autism at four biweekly sessions spanning the transition to arms-free sitting (infant age = 4.5-8 months at first session). At each session, infants sat on a pressure-sensitive mat with external support or independently, wore magneto-inertial sensors on both wrists, and reached for toys presented at midline. Analyses focused on characterizing and comparing control of sitting during reaching actions and standard kinematic metrics of reaching during Supported versus Independent Sitting. Although EL infants achieved arms-free sitting later than TL peers, there were no group differences on any measures. Across sessions, infants' control of the sitting posture during concurrent reaching movements improved in both contexts, though they were less stable as they reached when sitting independently compared to when sitting with support. A similar effect was apparent in the kinematics of reaches, with overall improvement over time, but evidence of poorer control in Independent relative to Supported Sitting. Taken together, these findings underscore the mutually influential and dynamic relations between emerging skills and well-established behaviors.

Biological and environmental factors may affect children's executive function through motor and sensorimotor development: Preterm birth and cerebral palsy

Disruptive biological and environmental factors may undermine the development of children's motor and sensorimotor skills. Since the development of cognitive skills, including executive function, is grounded in early motor and sensorimotor experiences, early delays or impairments in motor and sensorimotor processing often trigger dynamic developmental cascades that lead to suboptimal executive function outcomes. The purpose of this perspective paper is to link early differences in motor/sensorimotor processing to the development of executive function in children born preterm or with cerebral palsy. Uncovering such links in clinical populations would improve our understanding of developmental pathways and key motor and sensorimotor skills that are antecedent and foundational for the development of executive function. This knowledge will allow the refinement of early interventions targeting motor and sensorimotor skills with the goal of proactively improving executive function outcomes in at-risk populations.

Motor Overflow during Reaching in Infancy: Quantification of Limb Movement Using Inertial Motion Units

Early in life, infants exhibit motor overflow, which can be defined as the generation of involuntary movements accompanying purposeful actions. We present the results of a quantitative study exploring motor overflow in 4-month-old infants. This is the first study quantifying motor overflow with high accuracy and precision provided by Inertial Motion Units. The study aimed to investigate the motor activity across the non-acting limbs during goal-directed action. To this end, we used wearable motion trackers to measure infant motor activity during a baby-gym task designed to capture overflow during reaching movements. The analysis was conducted on the subsample of participants (n = 20), who performed at least four reaches during the task. A series of Granger causality tests revealed that the activity differed depending on the non-acting limb and the type of the reaching movement. Importantly, on average, the non-acting arm preceded the activation of the acting arm. In contrast, the activity of the acting arm was followed by the activation of the legs. This may be caused by their distinct purposes in supporting postural stability and efficiency of movement execution. Finally, our findings demonstrate the utility of wearable motion trackers for precise measurement of infant movement dynamics.

Infants at risk for physical disability may be identified by measures of postural control in supine

BACKGROUND

Early detection of delay or impairment in motor function is important to guide clinical management and inform prognosis during a critical window for the development of motor control in children. The purpose of this study was to investigate the ability of biomechanical measures of early postural control to distinguish infants with future impairment in motor control from their typically developing peers.

METHODS

We recorded postural control from infants lying in supine in several conditions. We compared various center of pressure metrics between infants grouped by birth status (preterm and full term) and by future motor outcome (impaired motor control and typical motor control).

RESULTS

One of the seven postural control metrics-path length-was consistently different between groups for both group classifications and for the majority of conditions.

CONCLUSIONS

Quantitative measures of early spontaneous infant movement may have promise to distinguish early in life between infants who are at risk for motor impairment or physical disability and those who will demonstrate typical motor control. Our observation that center of pressure path length may be a potential early marker of postural instability and motor control impairment needs further confirmation and further investigation to elucidate the responsible neuromotor mechanisms.

IMPACT

The key message of this article is that quantitative measures of infant postural control in supine may have promise to distinguish between infants who will demonstrate future motor impairment and those who will demonstrate typical motor control. One of seven postural control metrics-path length-was consistently different between groups. This metric may be an early marker of postural instability in infants at risk for physical disability.

Infant Reaching in the First Year of Life: A Scoping Review of Typical Development and Examples of Atypical Development

AIMS

Our objective was to identify the most common variables used for infant reaching assessment, describe values of these variables across the first year of life, and identify methodological considerations and knowledge gaps for future research.

METHODS

Studies were included if they met the following criteria: (1) assessed infant reaching in any position, (2) included a sample of infants with typical development: healthy, full-term, with no known impairments, (3) infants were under one year old at the first data collection, and (4) counted successful reaches resulting in object contact.

RESULTS

We identified 6 commonly assessed kinematic reaching variables: frequency, duration, movement units, peak velocity, average velocity, and straightness index. Methodological inconsistencies limit our ability to interpret values of these variables across studies.

CONCLUSIONS

Eliminating inconsistencies in study design and data analysis methods is the next step to defining a normative reference standard for reaching development. Establishing a normative reference standard for reaching in the first year of life will be important for assessment of typical and atypical reaching development.

Reaching skills in six-month-old infants at environmental and biological risk

OBJECTIVES

To assess kinematic parameters and proximal and distal reaching adjustments of infants at biological or environmental risk and compare with reaching performance of six-month-old full-term infants without known risk factors.

METHODS

This blinded cross-sectional study included 62 infants at six months of age divided into three independent groups: Group with no known risk factor (NRF), 28 full-terms with no risk factors; Low SES group (LSES):19 full-terms classified as low socioeconomic status and no biological risk; Very preterm group (VPT), 15 very preterm infants at six months corrected age and no environmental risk. Infants were placed in a reclined baby chair at 45°, and a malleable and unfamiliar object was presented to the infant at 5-second intervals to elicit reaching movements.

RESULTS

Infants from LSES presented reaching duration (p = 0.032, Cohen's f = 0.349) and movement unit (p = 0.033, Cohen's f = 0.351) significantly higher than VPT group. Horizontal hand orientation was moderately associated with infants at environmental risk (p = 0.031; Cramer's V = 0.30).

CONCLUSION

Infants of low socioeconomic status perform less functional reaching movements than very preterm infants at six months corrected age. Socioeconomic status may impact more on reaching skills than biological risk. Given the importance of reaching for infant development, low-cost public health strategies are needed to identify possible delays.

Effect of Core Stability Exercises on Hand Functions in Children With Hemiplegic Cerebral Palsy

Objective

To investigate the effectiveness of core stability exercises on hand functions in children with hemiplegic cerebral palsy.

Methods

Fifty-two children with hemiplegic cerebral palsy ranging in age from 6 years to 8 years were enrolled in this study. They were randomly assigned to two (control and study) groups. The control group received the selected physiotherapy exercises, and the study group received the same selected physiotherapy exercise program and core stability exercises. Time motor performance, gross manual dexterity, and upper extremity skills assessed using the Jebsen Taylor Hand Function Test, Box and Block Test, and Quality Upper Extremity Skill Test, respectively, were measured before and after 12 weeks of the treatment program.

Results

There were significant improvements in both groups by comparing the mean values of all measured variables before and after treatment (p<0.05). There were significant differences between the control and study groups with respect to all measured variables when comparing the post-treatment outcomes (p<0.05).

Conclusion

This study suggests that core stability exercises can be an effective intervention that may improve hand functions in children with hemiplegic cerebral palsy.

Feasibility and Effectiveness of Intervention With the Playskin Lift Exoskeletal Garment for Infants at Risk

BACKGROUND

Infants born preterm and/or with brain injury often exhibit delays in the development of reaching and object exploration, increasing their risk of associated delays in cognitive development.

OBJECTIVE

The objective of this study was to longitudinally evaluate feasibility of use of the novel Playskin Lift exoskeletal garment (Playskin; developed and trademarked by Dr. Lobo's Super Suits FUNctional Fashion and Wearable Technology Program at the University of Delaware, Newark, DE, USA), the assistive and rehabilitative effects of intervention with the garment on reaching and object exploration ability, and to relate changes in reaching and object exploration to changes in cognition during intervention for infants at risk for developmental delays.

DESIGN

A multiple baseline single-case design with 1- to 2-month Baseline, 4-month Intervention, and 1-month Postintervention phases was implemented.

METHODS

Ten infants born preterm and/or with brain injury, mean [SD] age 2.2 [1.3] months at the beginning of the study, were assessed biweekly throughout the study both with and without the Playskin Lift. Assessments included a Reaching Assessment and the cognitive subscale of the Bayley Scales of Infant and Toddler Development. Reaching and object exploration behaviors were coded from videos of the Reaching Assessment. Results were analyzed using multilevel modeling in SAS.

RESULTS

The Playskin Lift improved infants' reaching ability, hand orientation for grasp and object exploration, and multimodal object exploration when worn within sessions, especially during the Intervention phase. The garment also improved independent reaching and object exploration across time during the Intervention phase, with retention of gains in the Postintervention phase. Improvement in reaching ability was positively related to changes in cognitive outcomes during the Intervention phase.

LIMITATIONS

Limitations included modest sample size and the potential confounds of development and experience with time.

CONCLUSIONS

The Playskin Lift can serve as a feasible, effective, and accessible assistive and rehabilitative device to advance reaching, object exploration, and cognition for infants at risk for future delays.

Motor performance in a shape sorter task: A longitudinal study from 14 to 36 months of age in children with an older sibling ASD

During development, motor skills are fundamental in supporting interactions with the external world. The ability to plan actions is a particularly important aspect of motor skill since it is involved in many daily activities. In this work, we studied the development of motor planning longitudinally in children with an older sibling with Autism Spectrum Disorder (ASD) who are at heightened risk (HR) for the disorder and children with no such risk (low risk; LR) using a shape sorter task. Children were observed at 14, 18, 24 and 36 months. Three HR children with a later diagnosis of ASD (HR-ASD) were analyzed separately from the rest of the sample. Behavioral and kinematic data indicated that precision demands significantly influenced children's actions, and that children's performance improved with age. No differences were found between the HR and LR groups, but a descriptive analysis of data from the three HR-ASD suggested differences in the variables describing children's action (as reaching time and acceleration) as well as variables describing children's performance (as the adjustment of the shapes).

Early human motor development: From variation to the ability to vary and adapt

This review summarizes early human motor development. From early fetal age motor behavior is based on spontaneous neural activity: activity of networks in the brainstem and spinal cord that is modulated by supraspinal activity. The supraspinal activity, first primarily brought about by the cortical subplate, later by the cortical plate, induces movement variation. Initially, movement variation especially serves exploration; its associated afferent information is primarily used to sculpt the developing nervous system, and less to adapt motor behavior. In the next phase, beginning at function-specific ages, movement variation starts to serve adaptation. In sucking and swallowing, this phase emerges shortly before term age. In speech, gross and fine motor development, it emerges from 3 to 4 months post-term onwards, i.e., when developmental focus in the primary sensory and motor cortices has shifted to the permanent cortical circuitries. With increasing age and increasing trial-and-error exploration, the infant improves its ability to use adaptive and efficicient forms of upright gross motor behavior, manual activities and vocalizations belonging to the native language.

Developmental Trajectories of Hand Movements in Typical Infants and Those at Risk of Developmental Disorders: An Observational Study of Kinematics during the First Year of Life

Highlights

The kinematics of hand movements (spatial use, curvature, acceleration, and velocity) of infants with their mothers in an interactive setting

are significantly associated with age in cohorts of typical and at-risk infants

differ significantly at 5–6 months of age, depending on the context: relating either with an object or a person.

Environmental and developmental factors shape the developmental trajectories of hand movements in different cohorts: environment for infants with VIMs; stage of development for premature infants and those with West syndrome; and both factors for infants with orality disorders.

The curvature of hand movements specifically reflects atypical development in infants with West syndrome when developmental age is considered.

We aimed to discriminate between typical and atypical developmental trajectory patterns of at-risk infants in an interactive setting in this observational and longitudinal study, with the assumption that hand movements (HM) reflect preverbal communication and its disorders. We examined the developmental trajectories of HM in five cohorts of at-risk infants and one control cohort, followed from ages 2 to 10 months: 25 West syndrome (WS), 13 preterm birth (PB), 16 orality disorder (OD), 14 with visually impaired mothers (VIM), 7 early hospitalization (EH), and 19 typically developing infants (TD). Video-recorded data were collected in three different structured interactive contexts. Descriptors of the hand motion were used to examine the extent to which HM were associated with age and cohort. We obtained four principal results: (i) the kinematics of HM (spatial use, curvature, acceleration, and velocity) were significantly associated with age in all cohorts; (ii) HM significantly differed at 5–6 months of age in TD infants, depending on the context; (iii) environmental and developmental factors shaped the developmental trajectories of HM in different cohorts: environment for VIM, development for PB and WS, and both factors for OD and; (iv) the curvatures of HM showed atypical development in WS infants when developmental age was considered. These findings support the importance of using kinematics of HM to identify very early developmental disorders in an interactive context and would allow early prevention and intervention for at-risk infants.

Best seating condition in children with spastic cerebral palsy: One type does not fit all

BACKGROUND

The effect of forward-tilting of the seat surface and foot-support in children with spastic cerebral palsy (CP) is debated.

AIM

To assess the effect of forward-tilting of the seat surface and foot-support in children with CP on kinematic head stability and reaching.

METHODS

Nineteen children functioning at Gross Motor Function Classification System levels I-III participated [range 6-12y; ten unilateral spastic CP (US-CP) and nine bilateral spastic CP (BS-CP)]. Kinematic data were recorded of head sway and reaching with the dominant arm in four sitting conditions: a horizontal and a 15° forward (FW) tilted seat surface, each with and without foot-support.

RESULTS

Seating condition did not affect head stability during reaching, but did affect kinematic reaching quality. The major reaching parameters, i.e., the proportion of reaches with one movement unit (MU) and the size of the transport MU, were not affected by foot-support. Forward-tilting had a positive effect on these parameters in children with US-CP, whereas the horizontal condition had this effect in children with BS-CP.

IMPLICATIONS

A 15° forward-tilted seating and foot-support do not affect head stability. Reaching in children with US-CP profits from forward-tilting; in children with BS-CP forward-tilting worsens reaching - effects that are independent of foot-support.

Development of the quality of reaching in infants with cerebral palsy: a kinematic study

AIM

To assess development of reaching and head stability in infants at very high risk (VHR-infants) of cerebral palsy (CP) who did and did not develop CP.

METHOD

This explorative longitudinal study assessed the kinematics of reaching and head sway in sitting in 37 VHR-infants (18 CP) one to four times between 4.7 months and 22.6 months corrected age. Developmental trajectories were calculated using linear mixed effect models. Motor function was evaluated with the Infant Motor Profile (IMP) around 13 months corrected age.

RESULTS

Throughout infancy, VHR-infants with CP had a worse reaching quality than infants without CP, reflected for example by more movement units (factor 1.52, 95% CI 1.16-1.99) and smaller transport movement units (factor 1.86, 95% CI 1.20-2.90). Total head sway of infants with and without CP was similar, but infants with CP used more head movement units to achieve stability. The rate of developmental change in infants with and without CP was similar. Around 13 months, head control and reaching quality were interrelated; both were associated with IMP-scores.

INTERPRETATION

Infants with CP showed a worse kinematic reaching quality and head stability throughout infancy from early age onwards than VHR-infants without CP, implying that kinematically they do not grow into a deficit, but exhibit deficits from early infancy on.

WHAT THIS PAPER ADDS

Reaching quality improves throughout infancy in all infants at high risk (VHR-infants). Infants with cerebral palsy (CP) show a worse reaching quality than VHR-infants without CP. Infants with CP achieve head stability differently from infants without CP. Infants with CP exhibit kinematic reaching problems from early age onwards.

REACH: study protocol of a randomised trial of rehabilitation very early in congenital hemiplegia

OBJECTIVES

Congenital hemiplegia is the most common form of cerebral palsy (CP). Children with unilateral CP show signs of upper limb asymmetry by 8 months corrected age (ca) but are frequently not referred to therapy until after 12 months ca. This study compares the efficacy of infant-friendly modified constraint-induced movement therapy (Baby mCIMT) to infant friendly bimanual therapy (Baby BIM) on upper limb, cognitive and neuroplasticity outcomes in a multisite randomised comparison trial.

METHODS AND ANALYSIS

150 infants (75 in each group), aged between 3 and 6 months ca, with asymmetric brain injury and clinical signs of upper extremity asymmetry will be recruited. Children will be randomised centrally to receive equal doses of either Baby mCIMT or Baby BIM. Baby mCIMT comprises restraint of the unimpaired hand using a simple restraint (eg, glove, sock), combined with intensive parent implemented practice focusing on active use of the impaired hand in a play-based context. In contrast, Baby BIM promotes active play requiring both hands in a play-based context. Both interventions will be delivered by parents at home with monthly home visits and interim telecommunication support by study therapists. Assessments will be conducted at study entry; at 6, 12 months ca immediately postintervention (primary outcome) and 24 months ca (retention). The primary outcome will be the Mini-Assisting Hand Assessment. Secondary outcomes include the Bayley Scale for Infant and Toddler Development (cognitive and motor domains) and the Hand Assessment of Infants. A subset of children will undertake MRI scans at 24 months ca to evaluate brain lesion severity and brain (re)organisation after intervention.

ETHICS AND DISSEMINATION

Full ethical approvals for this study have been obtained from the relevant sites. The findings will be disseminated in peer-reviewed publications.

TRIAL REGISTRATION NUMBER

Australian and New Zealand Clinical Trials Registry: ACTRN12615000180516, Pre results.

Immediate Effect of Training at the Onset of Reaching in Preterm Infants: Randomized Clinical Trial

The authors' aim was to investigate the immediate effect of a single specific training session (serial varied practice), of short duration on the kinematic parameters of reaching, in the period of the emergence of the skill in preterm and low birth weight infants. The study included 16 infants of both sexes, born at a mean gestational age of 32.13 (±1.36) weeks and mean birth weight of 1720.94 (±358.46) g. The infants were randomly divided into 2 groups: experimental and control. The experimental group was given a 5-min training session in reaching, while the control group received no training. The results showed significant differences in peak velocity in the intra (Z = -2.10, p = .036) and intergroup (U = 9.00, p = .016) evaluations, which decreased in the experimental group after training. Cohen's d test for clinical relevance suggested that the specific, short duration training proved effective in promoting slower reaches, with greater adjustment and lower number of units of movement. These results are positive for preterm infants given that these parameters more closely resemble the typical development of mature reaching behaviors in term infants, which suggests that this protocol of reaching training (serial varied practice) could be used as an evidence-based intervention strategy.

Sitting postural control affects the development of focused attention in children with cerebral palsy

PURPOSE

To investigate whether focused attention (FA) changes over time as sitting postural control improves and whether an impairment in sitting postural control affects the development of FA in children with cerebral palsy (CP).

METHODS

Nineteen children with CP, mean ages 21.47 months, were assessed for FA and sitting scores pre- and postintervention.

RESULTS

Longest, total, and global FA increased and frequency of FA decreased in children who achieved independent sitting. However, children who achieved mobility postintervention exhibited a decrease in longest FA and an increase in frequency of FA.

CONCLUSION

Sitting postural control and the development of FA appear associated in children with CP. The increase in FA may signal a key opportunity for learning and attending to objects. However, the time of early mobility may interrupt these long periods of attention, resulting in less sustained attention to objects.

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.

Postural position constrains multimodal object exploration in infants

Recent research has revealed the important role of multimodal object exploration in infants' cognitive and social development. Yet, the real time effects of postural position on infants' object exploration have been largely ignored. In the current study, 5- to 7-month-old infants (N = 29) handled objects while placed in supported sitting, supine, and prone postures, and their spontaneous exploratory behaviors were observed. Infants produced more manual, oral, and visual exploration in sitting compared to lying supine and prone. Moreover, while sitting, infants more often coupled manual exploration with mouthing and visual examination. Infants' opportunities for learning from object exploration are embedded within a real time postural context that constrains the quantity and quality of exploratory behavior.

Typical and atypical development of reaching and postural control in infancy

Successful reaching requires postural control, either by active regulation or by postural support. The present paper reviews literature on typical and atypical development of reaching and postural control during infancy. Typically, reaching movements end in grasping around 4 months of age. Initially, reaches are characterized by large variation, including many trajectory corrections. During the first year, the movements get increasingly straight and smooth. Reaching in low-risk preterm infants is initially characterized by advanced development, but minor impairments may emerge in the second half of infancy. In high-risk preterm infants, development of reaching is characterized by delay and non-optimal reaching performance. Typical development of postural adjustments is characterized by variation and an increasing ability to adapt the variable repertoire to the specifics of the situation. The latter is facilitated by an increasing role of anticipatory mechanisms in the second half of infancy. Atypically developing infants may have a reduced repertoire and usually have difficulties in adapting postural adjustments. In infancy, most reaching movements are performed during sitting. The postural challenge of sitting may interfere in particular with the development of reaching in atypically developing infants. The practical implications of this suggestion are discussed.

Posture support improves object individuation in infants

A hierarchical progression in infants' ability to use surface features, such as color, as a basis for object individuation in the first year has been well established (Tremoulet, Leslie, & Hall, 2000; Wilcox, 1999). There is evidence, however, that infants' sensitivity to surface features can be increased through multisensory (i.e., visuohaptic) exploration of objects (Wilcox, Woods, Chapa, & McCurry, 2007). Three studies were conducted to investigate the effect of multisensory experience on infants' sensitivity to pattern information. Experiments 1 and 2 confirmed that 5.5- and 6.5-month-olds do not spontaneously use pattern differences to individuate objects and revealed that 6.5- but not 5.5-month-olds can be primed to attend to pattern differences if allowed multisensory experience with the objects prior to the individuation task. However, the 5.5-month-olds also had greater difficulty maintaining a self-sitting posture during the multisensory priming experience. In Experiment 3, 4.5- and 5.5-month-olds were given full postural support during the multisensory exploration period. In this situation, the 5.5-month-olds successfully individuated the objects, but even with full postural support, 4.5-month-old infants did not use the pattern differences to individuate the objects. These results demonstrate that multisensory priming is effective with infants as young as 5.5 months and extends multisensory priming to another surface feature, pattern. Furthermore, these results indicate that constraints are placed on the multisensory experience by the physical and motor development of the infant.

Segmental trunk control acquisition and reaching in typically developing infants

This study explored the influence of an external support at the thoracic and pelvic level of the trunk on the success of reaching, postural stability and reaching kinematics while infants reached for a toy. Seventeen infants (4-6 months) were clustered into two groups according to their trunk control assessed with the Segmental Assessment of Trunk Control. Major differences were seen between groups with pelvic support, whereas with thoracic support, all infants showed similar quality reaching behaviors. With the external pelvic support, infants who had acquired trunk control in the lumbar region were more accurate in their reaching movements (less movement time, improved straightness of reach, less movement units and increased path length per movement unit) and were more stable (decreased trunk and head displacement) during a reach than infants who had only acquired trunk control in the thoracic region. These results support the hypothesis that trunk control influences the quality of reaching behavior.

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.

On the other hand: overflow movements of infants' hands and legs during unimanual object exploration

Motor overflow is extraneous movement in a limb not involved in a motor action. Typically, overflow is observed in people with neurological impairments and in healthy children and adults during strenuous and attention-demanding tasks. In the current study, we found that young infants produce vast amounts of motor overflow, corroborating claims of symmetry being the default state of the motor system. While manipulating an object with one hand, all 27 of the typically developing 4.5- to 7.5-month-old infants who we observed displayed overflow movements of the free hand (on 4/5 of unimanual actions). Mirror-image movements of the hands occurred on 1/8 of unimanual actions, and the hands and legs moved in synchrony on 1/3 of unimanual acts. Motor overflow was less frequent when infants were in a sitting posture and when infants watched their acting hand, suggesting that upright posture and visual examination may help to alleviate overflow and break obligatory symmetry in healthy infants.

Longitudinal study of unimanual actions and grasping forces during infancy

Learning to grasp an object is an important milestone in neurological development during infancy. Several studies report development of reaching in infants but less attention is devoted to reaching with successful grasping and to development of grip force. This study investigates, in the first weeks of life, the development of palmar grasp both for assessment of unimanual/bimanual grasping actions in centrally and laterally placed objects and for measurement of exerted power grip force. We longitudinally examined ten infants from 18 weeks to 41 weeks, at 2-weeks intervals, with a toy placed in three positions (body midline, ipsilateral and contralateral shoulder). Our main aim was to study this development through an ecological approach. This was possible thanks to the use of the "biomechatronic gym", a new platform purposively developed for measuring reaching and grasping forces. These longitudinal trials showed a good level of acceptance and involvement by infants of the entire system. The results demonstrated a significant increase in unimanual power grip force between the 18th and 30th week followed by a flat period until the 41st week; we also ascertained an early tendency to play bimanually with centrally and laterally placed objects with a subsequent increase in all ages of unimanual successful power grasping both for central task and midline crossing. These developmental changes may be, in part, related to organism constraints such as maturation of the corticospinal tract.

Relationship Between Postural Control and Fine Motor Skills in Preterm Infants at 6 and 12 Months Adjusted Age

We examined the relationship between postural control and fine motor skills of preterm infants at 6 and 12 mo adjusted age. The Alberta Infant Motor Scale was used to measure postural control, and the Peabody Developmental Motor Scales II was used to measure fine motor skills. The data analyzed were taken from 105 medical records from a preterm infant follow-up clinic at an urban academic medical center in south Taiwan. Using multiple regression analyses, we found that the development of postural control is related to the development of fine motor skills, especially in the group of preterm infants with delayed postural control. This finding supports the theoretical assumption of proximal–distal development used by many occupational therapists to guide intervention. Further research is suggested to corroborate findings.

Proximal and distal adjustments of reaching behavior in preterm infants

The authors aimed to investigate proximal and distal adjustments of reaching behavior and grasping in 5-, 6-, and 7-month-old preterm infants. Nine low-risk preterm and 10 full-term infants participated. Both groups showed the predominance of unimanual reaching, an age-related increase in the frequency of vertical-oriented and open hand movement, and also an increase in successful grasping from 6 to 7 months. The frequency of open hand was higher in the preterm group at 6 months. Intrinsic restrictions imposed by prematurity did not seem to have impaired reaching performance of preterm infants throughout the months of age.

Influência da posição do objeto na frequência de alcances manuais em lactentes com desenvolvimento típico

O objetivo deste estudo foi verificar a frequência de alcances no período de três a cinco meses de idade e se há influência da posição de apresentação do objeto. Treze lactentes com desenvolvimento típico foram avaliados aos três, quatro e cinco meses, em supino, sendo o objeto apresentado na linha média e nas linhas axilares direita e esquerda. O procedimento foi filmado e analisado para registro do número de alcances realizados nas posições de apresentação. Para análise foram utilizados os testes de Friedman e Wilcoxon, considerando o nível de significância α=0,05. As frequências médias de alcances aumentaram até o quinto mês, sendo encontrada diferença significativa entre o terceiro e o quinto (p=0,011) e entre o quarto e o quinto meses (p=0,008). O número de alcances na linha média aumentou significativamente do terceiro para o quinto (p=0,011) e do quarto para o quinto mês (p=0,025), e houve tendência de diferenciação (0,1>p>0,05) entre o terceiro e o quarto mês (p=0,058). Aos três meses, encontrou-se tendência de diferenciação (p=0,066) entre a frequência de alcances nas linhas axilar (D ou E) e média. Aos quatro e cinco meses, não foi encontrada diferença estatisticamente significativa entre as posições. Concluiu-se que a frequência de alcances aumenta significativamente de três a cinco meses e a posição de apresentação do objeto parece influenciá-la na fase inicial de aquisição desta habilidade.

How do object size and rigidity affect reaching and grasping in infants with Down syndrome?

Reaching and grasping skills have been described to emerge from a dynamic interaction between intrinsic and extrinsic factors. The purpose of the present study was to investigate the interaction between such an intrinsic factor, Down syndrome, and extrinsic factors, such as different object properties. Seven infants with Down syndrome and seven infants with typical development were assessed at the ages of 4, 5 and 6 months. The findings showed that object size influenced the kinematics of reaching for the infants with Down syndrome and the grasping frequency for the typical infants. The object rigidity was shown to have a major influence on grasping frequency.

Preferência manual de crianças ao alcançar objetos de tamanho e rigidez diferentes

O estudo teve por objetivo analisar a preferência manual de crianças ao alcançar objetos de diferentes tamanhos nas idades de 4, 6, 8 e 36 meses. Para tanto, nove crianças saudáveis foram posicionadas em uma cadeira reclinada para trás a 50º com a horizontal e a elas foram apresentados quatro objetos de rigidez e tamanhos distintos. Foram coletados longitudinalmente 524 alcances aos 4, 6, 8 e 36 meses, sendo analisadas as variáveis mão preferida no alcance e índice de contribuição para os alcances bimanuais. Constatou-se que a mão preferida no alcance no decorrer dos meses foi a direita e que somente aos 6 meses o tamanho dos objetos influenciou a preferência manual: as crianças fizeram preferencialmente alcances com a mão direita para objetos pequenos, e mão esquerda para os grandes. Nos alcances bimanuais, constatou-se que, em geral, a mão que primeiro toca o objeto é a mão mais ativa durante todo o movimento de alcançar. Provavelmente porque a rigidez seja menos visualmente percebida do que o tamanho, só este influencia o alcance aos 6 meses, idade em que o lactente refina o movimento de alcance. O tamanho o influencia aos 6 meses, idade em que o movimento de alcançar se encontra em fase de refinamento: objetos pequenos que exigem maior precisão foram alcançados com a mão direita (mão preferida); e objetos grandes, que não exigem precisão para serem apreendidos, foram alcançados com a mão esquerda.

Infants born preterm exhibit different patterns of center-of-pressure movement than infants born at full term

BACKGROUND

Infants born preterm are at risk for developmental impairments related to postural control.

OBJECTIVE

The purpose of this study was to determine whether infants born preterm and infants born at full term differed in postural control at 1 to 3 weeks after term age.

DESIGN

This study included 17 infants born preterm (mean gestational age=31.9 weeks, range=25.0-34.6) and 15 infants born at full term (mean gestational age=38.9 weeks, range=37.3-40.6). All infants were without diagnosed neurological or genetic conditions.

MEASUREMENT

Center-of-pressure (COP) data were recorded at 5 Hz while each infant was positioned supine on a pressure-sensitive mat in an alert behavioral state. Root mean square (RMS) displacement and approximate entropy (ApEn) were used to describe the COP movement variability in the time series. Differences between groups were identified using independent t tests.

RESULTS

The COP time series were found to be deterministic, suggesting order in the time series. Infants born preterm exhibited significantly larger RMS values in the caudal-cephalic direction than infants born at full term (1.11 and 0.83 cm, respectively; t=-2.6, df=30, P=.01). However, infants born at full term had significantly larger ApEn values in the caudal-cephalic direction (1.19 and 1.11, respectively; t=2.4, df=30, P=.02). The 2 groups did not differ in RMS or ApEn values in the medial-lateral direction or the resultant.

CONCLUSIONS

Infants born at full term exhibited COP displacements in the caudal-cephalic direction that were smaller in amplitude, but may be considered more complex or less predictable, than those of infants born preterm. One explanation is that infants born preterm exhibited more stereotypic patterns of movement, resulting in large, but repetitive, COP excursions. A combination of linear and nonlinear measures may provide insight into the control of posture of young infants.

Development of proximal arm muscle control during reaching in young infants: from variation to selection

Reaching movements are initiated by activity of the prime mover, i.e. the first activated arm muscle. We aimed to investigate the relationship between prime mover activity and kinematics of reaching in typically developing (TD) infants in supine and sitting position. Fourteen infants were assessed at 4 and 6 months during reaching in supine and supported sitting. Kinematics and EMG-activity of deltoid, pectoralis major, biceps (BB) and triceps brachii were recorded. Kinematic analysis focused on number of movement units (MUs) and transport MU (MU with longest duration). Prime mover use was variable, but at 6 months a dominance of BB emerged in both testing conditions. Kinematics were also variable, but with increasing age the number of MU decreased and the relative proportion of the transport MU increased. BB as prime mover at 6 months was related to a larger transport MU.

CONCLUSION

Between 4 and 6 months BB prime mover dominance emerges which is related to relatively efficient reaching characteristics.

Reaching and grasping movements in infants at risk: a review

Although the influence of intrinsic and extrinsic factors on the development of reaching and grasping skills in typical infants has been extensively described in the literature, the effect of such factors on at-risk infants is still poorly understood. Therefore, the aims of the present study were to analyze the scientific publications, from 1980 to 2008, about factors influencing reaching and grasping movements in infants at risk and to describe methodological procedures used in the studies under review. A bibliographical review on empirical studies indexed on Medline, Lilacs and Science Direct data bases was done, using as keywords the terms: "reaching movements", "grasping", "catching", "prehension", "infants", "children", "risk", "deficit", "impairment" and "delay". 127 articles were identified, and 11 were selected. The following risk conditions were assessed in the papers: prematurity, cerebral palsy, Down syndrome, intrauterine cocaine exposure and agenesis of corpus callosum. Methodological issues as well as the intrinsic and extrinsic factors manipulated in the experiments are discussed in the light of changes in theoretical approach to motor behavior.

Variability in the levels of postural control in 0-4-month-old infants

This prospective cross-sectional study aimed to characterize variability in the levels of postural control in supine and prone positions in typical 0-4-month-old infants by using the Chailey Levels of Abilities Scale. Forty infants were divided into five groups of eight infants, according to their age. In supine, the levels varied between 1 and 2 in 0-month group, and between 2 and 3 in 2-month group. In prone, the levels varied between 1 and 2 in both 0- and 1-month groups. There was no variability in 1-month group in supine or in 2-month group in prone. In 3-month and 4-month groups, no variability was found in any of the positions. Variability in the levels of postural control among infants at the same age may be interpreted as normal as long as infants are in the initial process of acquiring postural control, that is, within the age range of 0-2 months.

Time series analysis of spontaneous upper-extremity movements of premature infants with brain injuries

BACKGROUND AND PURPOSE

Comparisons of spontaneous movements of premature infants with brain injuries and those without brain injuries can provide insights into normal and abnormal processes in the ontogeny of motor development. In this study, the characteristics of spontaneous upper-extremity movements of premature infants with brain injuries and those without brain injuries were examined with time series analysis.

SUBJECTS

Participants were 7 premature infants with brain injuries and 7 matched, low-risk, premature infants at the age of 1 month after term.

METHODS

A triaxial accelerometer was used to measure upper-extremity limb acceleration in 3-dimensional space. Acceleration signals were recorded from the right wrist when the infant was in an active, alert state and lying in the supine position. The recording time was 200 seconds. The acceleration signal was sampled at a rate of 200 Hz. The acceleration time series data were analyzed by nonlinear analysis as well as linear analysis.

RESULTS

The nonlinear time series analysis indicated that spontaneous movements of premature infants have nonlinear, chaotic, dynamic characteristics. The movements of the infants with brain injuries were characterized by larger dimensionality, and they were more unstable and unpredictable than those of infants without brain injuries.

DISCUSSION AND CONCLUSION

As determined by nonlinear analysis, the spontaneous movements of the premature infants with brain injuries had the characteristics of increased disorganization compared with those of the infants without brain injuries. Infants with brain injuries may manifest problems with self-organization as a function of the coordination of subsystems. Physical therapists should be able to support interactions among the subsystems and promote self-organization of motor learning through the individualized provision of various sensorimotor experiences for infants.

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.

Movement training advances the emergence of reaching in infants born at less than 33 weeks of gestational age: a randomized clinical trial

BACKGROUND AND PURPOSE

This study had 2 purposes: (1) to compare the emergence of reaching in infants born full-term and infants born at less than 33 weeks of gestational age and (2) to evaluate the effectiveness of a movement training program on the emergence of reaching in this preterm population.

PARTICIPANTS

Twenty-six infants born at less than 33 weeks of gestational age and with a birth weight less than 2,500 g were randomly assigned to receive 20 minutes of daily movement training (PT-M group) or daily social training (PT-S group) and were compared with 13 infants born full-term (FT-S group).

METHODS

Reaching and hand-object interactions were tested every other week for 8 weeks. At each visit, infants were allowed six 30-second opportunities to contact a midline toy.

RESULTS

The FT-S and PT-M groups reached earlier and more consistently than the PT-S group. Specifically, the subjects in the FT-S group contacted the toy for longer durations and with an open, ventral surface of their hand. The PT-M group demonstrated increases in the number of hand-object contacts, the number of consistent reaches, and the percentage of time interacting with the toy and the surface of hand-object contact.

DISCUSSION AND CONCLUSION

This project demonstrates that there are early gross motor skill differences in infants born at less than 33 weeks of gestational age. A caregiver-based daily training program, however, is effective at lessening some, but not all, of these differences over the short term.

The influence of lying positions and postural control on hand-mouth and hand-hand behaviors in 0-4-month-old infants

The purpose of this study was to verify how and when body position and postural control affect hand-mouth and hand-hand behaviors in infants during their first 4 months of life. Forty healthy infants were positioned in supine, prone and side-lying positions so that frequency and duration of the behaviors were quantified. Postural control when in supine and prone was also analyzed. The prone position elicited hand-mouth behavior in 0-2-month-old infants. The side-lying position elicited hand-mouth behavior in 3-4-month-old infants and hand-hand behavior in 2-4-month-olds. The increased postural control promoted the emergence of hand-hand behavior when in supine, and decreased hand-mouth behavior when in prone. The results show that self-exploratory behaviors may be affected not only by extrinsic constraints, represented by different body positions, but also by intrinsic constraints, represented by characteristic action possibilities and postural control of each age group.

Early control of reaching: effects of experience and body orientation

Although research suggests that experience may be a better indicator of the acquisition of certain abilities by infants than age, little work addresses this issue in the development of reaching movements in particular. This longitudinal study fills this gap by verifying the effect of practice time on more- and less-skilled reachers of the same age group in different body orientations. Less- (n=6) and more-skilled (n=4) reachers were evaluated at the acquisition of reaching and again after 1 month of spontaneous practice. Kinematic analyses examined 3D wrist motion during reaching trials in supine (0 degrees ), reclined (45 degrees ) and seated (70 degrees ) orientations. The results indicated that skill level was a relevant factor in dealing with gravitational constraints imposed by different body orientations. Time of practice affected the way less- and more-skilled reachers explored and adapted the kinematic parameters of reaching to constraints imposed by body orientations. These findings suggest that not only age, but also experience and body orientations are important constraints that should be taken into account when examining infant reaching development.

A dynamical systems analysis of spontaneous movements in newborn infants

The authors evaluated the characteristics of infants' spontaneous movements by using dynamical systems analysis. Participants were 6 healthy 1-month-old full-term newborn infants (3 males, 3 females). They used a triaxial accelerometer to measure limb acceleration in 3-dimensional space. Acceleration signals were recorded during 200 s from the right wrist when the infant was in an active alert state and lying supine (sampling rate 200 Hz). and was stored in the system's memory. Digitized data were transferred to a PC for subsequent processing with analysis software. The acceleration time series data were analyzed linearly and nonlinearly. Nonlinear time series analysis suggested that the infants' spontaneous movements are characterized by a nonlinear chaotic dynamics with 5 or 6 embedding dimensions. The production of infants'spontaneous movements involves chaotic dynamic systems that are capable of generating voluntary skill movements.

Postural adjustments and reaching in 4- and 6-month-old infants: an EMG and kinematical study

Adequate postural control is a prerequisite for daily activities such as reaching for an object. However, knowledge on the relationship between postural adjustments and the quality of reaching movements during human ontogeny is scarce. Therefore we evaluated the development of the relationship between the kinematic features of reaching movements and the accompanying postural adjustments in young infants. Twelve typically developing (TD) infants were assessed twice, i.e. at 4 and 6 months of age, in supine and supported sitting position. Reaching was elicited by presenting toys in the midline at an arm-length distance while simultaneously surface EMG-activity was recorded from multiple arm-, neck-, trunk- and leg muscles. Concurrently kinematics of reaching were recorded with an ELITE system; kinematic analysis was restricted to the behaviour of so-called movement units, which are sub movements of reaching determined with the help of peaks in the velocity profile of the hand, maximum movement velocity and movement duration. A computer-algorithm determined significant phasic muscle activity. Activity in neck and trunk muscles (postural activity) was related to the onset of the prime mover, which was the arm muscle being activated first. The results indicated that about 50% of reaching movements in lying and sitting infants aged 4 and 6 months were accompanied by direction-specific postural adjustments. At 4 months variation dominated, but at 6 months a preference to recruit muscles in a top-down order (during sitting) and in the configuration of the complete pattern, i.e. the pattern in which all dorsal neck- and trunk muscles are activated in concert, (both conditions) emerged. Interestingly, the postural characteristics such as the presence of direction-specificity, recruitment of the complete pattern and top-down recruitment, were related to how successful the reaching was and the kinematics of reaching. It was concluded that the presence of direction-specific activity is not a prerequisite for the emergence of reaching movements. Nevertheless, already from 4 months onwards a better postural control is associated with a larger success and a better quality of reaching.

Spatio-temporal parameters in infant's reaching movements are influenced by body orientation

Many studies have demonstrated that the seated position is more effective in promoting reaching movements when compared with supine. The aim of this longitudinal study was to verify the effect of seated and supine positions on spatio-temporal parameters of reaching in 4-6-month-old infants. Four infants were observed during reaching trials in both positions. A total of 235 reaches were analyzed by using the 3D movement reconstruction. Our results showed that frequency of reaching and straightness index increased over age. Significant differences between the positions were observed at 4 months, when the frequency increased and the duration and deceleration time decreased in the seated position. There were no significant differences at 5 and 6 months. These findings suggest that young infants are able to change kinematical parameters of reaching to adapt themselves to intrinsic and extrinsic constraints (i.e. age and position).

Motor Deficits in Parkinsonian Reaching: Dopa-Sensitivity Influenced by Real-World Task Constraint

Parkinson's disease (PD) patients can perform many daily activities, but movement deficits are evident. Those deficits may be increased when the required movement is constrained in accuracy. Variable improvements in performance with PD medication have been demonstrated, and sensitivity to task constraint has been evident in some studies. The authors quantified both specific movement deficits and improvements for PD patients in a reaching task. PD patients (N=8) both on and off medication showed a need for greater ongoing control in movements with higher task-accuracy constraints. Increased task-accuracy constraints further compromised movement timing and structure among PD patients who were off medication, suggesting that unmedicated PD patients may typically compensate by using more conscious control of movement, resulting in increased slowing and segmentation of components when higher task accuracy is required.