Early gait development in human infants: Plasticity and clinical applications

Natural-ish behavior: The interplay of culture and context in shaping motor behavior in infancy

What is natural behavior and how does it differ from laboratory-based behavior? The "natural" in natural behavior implies the everyday, complex, ever-changing, yet predictable environment in which children grow up. "Behavior" is motor action and is foundational to psychology, as it includes all things to function in everyday environments. Is behavior demonstrated in the laboratory un-natural? Suppose behavior emerges spontaneously, in a context that is most common to the animal but an observer is there to document it using particular research tools. Is that behavior natural or natural-ish? Methods can powerfully affect conclusions about infant experiences and learning. In the lab, tasks are typically narrowly constrained where infants and children have little opportunity to display the variety of behaviors in their repertoire. Data from naturalistic observations may paint a very different picture of learning and development from those based on structured tasks, exposing striking variability in the environment and behavior and new relations between the organism and its environment. Using motor development as a model system, in this chapter we compare frameworks, methods, and findings originating in the lab and in the field, applied and adapted in different settings. Specifically, we recount our journey of pursuing the study of cultural influences on motor development in Tajikistan, and the challenges, surprises, and lessons learned.

Complexity of modular neuromuscular control increases and variability decreases during human locomotor development

When does modular control of locomotion emerge during human development? One view is that modularity is not innate, being learnt over several months of experience. Alternatively, the basic motor modules are present at birth, but are subsequently reconfigured due to changing brain-body-environment interactions. One problem in identifying modular structures in stepping infants is the presence of noise. Here, using both simulated and experimental muscle activity data from stepping neonates, infants, preschoolers, and adults, we dissect the influence of noise, and identify modular structures in all individuals, including neonates. Complexity of modularity increases from the neonatal stage to adulthood at multiple levels of the motor infrastructure, from the intrinsic rhythmicity measured at the level of individual muscles activities, to the level of muscle synergies and of bilateral intermuscular network connectivity. Low complexity and high variability of neuromuscular signals attest neonatal immaturity, but they also involve potential benefits for learning locomotor tasks.

Toward Preventing Speech and Language Disorders of Known Genetic Origin: First Post-Intervention Results of Babble Boot Camp in Children With Classic Galactosemia

Purpose Babble Boot Camp (BBC) is a package of proactive activities and routines designed to prevent speech and language disorders in infants at predictable risk. It is implemented via parent training and currently undergoing clinical trial in children with a newborn diagnosis of classic galactosemia (CG), a metabolic disease with high risk of speech and language disorders. The purpose of this study is to provide updates to a previous pilot study and to present the first set of post-intervention results. Method The intervention and data collection occurred during child ages < 6-24 months, with follow-up assessments of speech and language at ages 2.5 and 3.5 years. Treatment targets included earliest vocalization rates, babble complexity, speech production accuracy, and vocabulary and syntactic growth. The oldest 15 children with CG (including three untreated controls) completed the first set of follow-up assessments. Aggregate data up to 10 months were available for 17 treated children with CG, six untreated children with CG, and six typical controls. Results At ages 7-9 months, babbling complexity, as measured with mean babbling level, was higher in the treated children with CG than in the untreated children with CG and the typical controls. Prior to 24 months of age, the treated children with CG had greater expressive but not receptive vocabulary sizes than an untreated control. Follow-up testing showed typical language scores for all 12 treated children with CG and typical articulation scores for 11 of these, whereas one of three untreated children with CG had low articulation and expressive language scores. Conclusions The BBC appears to be a viable intervention to support the speech and expressive language development of children with GC. Future studies will evaluate the relative contributions of the earliest and later BBC components to outcomes.

Can Optic Flow Further Stimulate Treadmill-Elicited Stepping in Newborns?

Typically developing 3-day-old newborns take significantly more forward steps on a moving treadmill belt than on a static belt. The current experiment examined whether projecting optic flows that specified forward motion onto the moving treadmill surface (black dots moving on the white treadmill surface) would further enhance forward stepping. Twenty newborns were supported on a moving treadmill without optic flow (No OF), with optic flow matching the treadmill’s direction and speed (Congruent), with optic flow in the same direction but at a faster speed (Faster), and in a control condition with an incoherent optic flow moving at the same speed as in the Congruent condition but in random directions (Random). The results revealed no significant differences in the number or coordination of forward treadmill steps taken in each condition. However, the Faster condition generated significantly fewer leg pumping movements than the Random control condition. When highly aroused, newborns made significantly fewer single steps and significantly more parallel steps and pumping movements. We speculate the null findings may be a function of the high friction material that covered the treadmill surface.

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

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

Development of vertical and forward jumping skills in typically developing children in the context of referent control of motor actions

The empirically based referent control theory of motor actions provides a new framework for understanding locomotor maturation. Mature movement patterns of referent control are characterized by periods of minimization of activity across multiple muscles (global electromyographic [EMG] minima) resulting from transient matching between actual and referent body configurations. We identified whether locomotor maturation in young children was associated with (a) development of referent control and (b) children's frequency of participation in everyday activities evaluated by parents. Kinematics and EMG activity were recorded from typically developing children (n = 15, 3-5 years) and young adults (n = 10, 18-25 years) while walking, vertical or forward jumping. Presence and location of global EMG minima in movement cycles, slopes of ankle vertical/sagittal displacements, and shoulder displacement ratios were evaluated. Children had fewer global EMG minima compared to adults during specific phases of vertical and forward jumps. Ankle displacement profiles for walking and jumping forward were related to each other in adults, whereas those for walking and vertical jumping were related in children. Higher frequency of participation was significantly correlated with more mature jumping patterns in children. A decrease in the number of global EMG minima and changes in ankle movement patterns could be indicators of locomotor immaturity in typically developing children.

Modularity underlying the performance of unusual locomotor tasks inspired by developmental milestones

Motor behaviors are often hypothesized to be set up from the combination of a small number of modules encoded in the central nervous system. These modules are thought to combine such that a variety of motor tasks can be realized, from reproducible tasks such as walking to more unusual locomotor tasks that typically exhibit more step-by-step variability. We investigated the impact of step-by-step variability on the modular architecture of unusual tasks compared with walking. To this aim, 20 adults had to perform walking and two unusual modes of locomotion inspired by developmental milestones (cruising and crawling). Sixteen surface electromyography (EMG) signals were recorded to extract both spatial and temporal modules. Modules were extracted from both averaged and nonaveraged (i.e., single step) EMG signals to assess the significance of step-to-step variability when participants practiced such unusual locomotor tasks. The number of modules extracted from averaged data was similar across tasks, but a higher number of modules was required to reconstruct nonaveraged EMG data of the unusual tasks. Although certain walking modules were shared with cruising and crawling, task-specific modules were necessary to account for the muscle patterns underlying these unusual locomotion modes. These results highlight a more complex modularity (e.g., more modules) for cruising and crawling compared with walking, which was only apparent when the step-to-step variability of EMG patterns was considered. This suggests that considering nonaveraged data is relevant when muscle modularity is studied, especially in motor tasks with high variability as in motor development.NEW & NOTEWORTHY This study addresses the general question of modularity in locomotor control. We demonstrate for the first time the importance of intraindividual variability in the muscle modularity of unusual locomotor behaviors that exhibit greater step-by-step variability than standard walking. Crawling and cruising, the unusual locomotor modes considered, are based on a more complex modular organization than walking. More spatial and temporal modules, task specific or shared with walking modules, are needed to reconstruct muscle patterns.

The neurological phenotype of developmental motor patterns during early childhood

INTRODUCTION

During early childhood, typical human motor behavior reveals a gradual transition from automatic motor patterns to acquired motor skills, by the continuous interplay between nature and nurture. During the wiring and shaping of the underlying motor networks, insight into the neurological phenotype of developmental motor patterns is incomplete. In healthy, typically developing children (0-3 years of age), we therefore aimed to investigate the neurological phenotype of developmental motor patterns.

METHODS

In 32 healthy, typically developing children (0-3 years), we video-recorded spontaneous motor behavior, general movements (GMs), and standardized motor tasks. We classified the motor patterns by: (a) the traditional neurodevelopmental approach, by Gestalt perception and (b) the classical neurological approach, by the clinical phenotypic determination of movement disorder features. We associated outcomes by Cramer's V.

RESULTS

Developmental motor patterns revealed (a) choreatic-like features (≤3 months; associated with fidgety GMs (r = 0.732) and startles (r = 0.687)), (b) myoclonic-like features (≤3 months; associated with fidgety GMs (r = 0.878) and startles (r = 0.808)), (c) dystonic-like features (0-3 years; associated with asymmetrical tonic neck reflex (r = 0.641) and voluntary movements (r = 0.517)), and (d) ataxic-like features (>3 months; associated with voluntary movements (r = 0.928)).

CONCLUSIONS

In healthy infants and toddlers (0-3 years), typical developmental motor patterns reveal choreatic-, myoclonic-, dystonic- and ataxic-like features. The transient character of these neurological phenotypes is placed in perspective of the physiological shaping of the underlying motor centers. Neurological phenotypic insight into developmental motor patterns can contribute to adequate discrimination between ontogenetic and initiating pathological movement features and to adequate interpretation of therapeutic interactions.

Automated functional upper limb evaluation of patients with Friedreich ataxia using serious games rehabilitation exercises

Background

Friedreich ataxia (FRDA) is a disease with neurological and systemic involvement. Clinical assessment tools commonly used for FRDA become less effective in evaluating decay in patients with advanced FRDA, particularly when they are in a wheelchair. Further motor worsening mainly impairs upper limb function. In this study, we tested if serious games (SG) developed for rehabilitation can be used as an assessment tool for upper limb function even in patients with advanced FRDA.

Methods

A specific SG has been developed for physical rehabilitation of patients suffering from neurologic diseases. The use of this SG, coupled with Kinect sensor, has been validated to perform functional evaluation of the upper limbs with healthy subjects across lifespan. Twenty-seven FRDA patients were included in the study. Patients were invited to perform upper limb rehabilitation exercises embedded in SG. Motions were recorded by the Kinect and clinically relevant parameters were extracted from the collected motions. We tested if the existence of correlations between the scores from the serious games and the severity of the disease using clinical assessment tools commonly used for FRDA. Results of patients were compared with a group a healthy subjects of similar age.

Results

Very highly significant differences were found for time required to perform the exercise (increase of 76%, t(68) = 7.22, P < 0.001) and for accuracy (decrease of 6%, t(68) = − 3.69, P < 0.001) between patients and healthy subjects. Concerning the patients significant correlations were found between age and time (R = 0.65, p = 0.015), accuracy (R = − 0.75, p = 0.004) and the total displacement of upper limbs. (R = 0.55, p = 0.031). Statistically significant correlations were found between the age of diagnosis and speed related parameters.

Conclusions

The results of this study indicate that SG reliably captures motor impairment of FRDA patients due to cerebellar and pyramidal involvement. Results also show that functional evaluation of FRDA patients can be performed during rehabilitation therapy embedded in games with the patient seated in a wheelchair.

Trial registration

The study was approved as a component of the EFACTS study (Clinicaltrials.gov identifier NCT02069509, registered May 2010) by the local institutional Ethics Committee (ref. P2010/132).

3D Analysis of Upper Limbs Motion during Rehabilitation Exercises Using the KinectTM Sensor: Development, Laboratory Validation and Clinical Application

Optoelectronic devices are the gold standard for 3D evaluation in clinics, but due to the complexity of this kind of hardware and the lack of access for patients, affordable, transportable, and easy-to-use systems must be developed to be largely used in daily clinics. The Kinect^TM sensor has various advantages compared to optoelectronic devices, such as its price and transportability. However, it also has some limitations: (in)accuracy of the skeleton detection and tracking as well as the limited amount of available points, which makes 3D evaluation impossible. To overcome these limitations, a novel method has been developed to perform 3D evaluation of the upper limbs. This system is coupled to rehabilitation exercises, allowing functional evaluation while performing physical rehabilitation. To validate this new approach, a two-step method was used. The first step was a laboratory validation where the results obtained with the Kinect^TM were compared with the results obtained with an optoelectronic device; 40 healthy young adults participated in this first part. The second step was to determine the clinical relevance of this kind of measurement. Results of the healthy subjects were compared with a group of 22 elderly adults and a group of 10 chronic stroke patients to determine if different patterns could be observed. The new methodology and the different steps of the validations are presented in this paper.

Suitability of functional evaluation embedded in serious game rehabilitation exercises to assess motor development across lifespan

The aim of this study was to determine if the results of activities performed using specially developed serious games for physical rehabilitation could be used as an indicator of the natural maturation and decline of motor control in healthy participants. Eighty-one participants (19 children (5-15 years old), 40 adults (18-65 years old) and 22 aged subjects (60-88 years old) participated in this study. Motions performed were recorded using the Kinect sensor. Three different exercises embedded in the games were used to assess upper limb, trunk and lower limb control. The trial duration and accuracy, measures of gross motor function and fine motor control, respectively, were computed for each participant. ANOVA tests shows statistically significant differences between the three groups for duration (53±15, 27±10 and 119±30s for children, adults and elderly subjects respectively) and accuracy (87±5, 89±10 and 70±8% for children, adults and elderly subjects respectively). The slopes of the curves that approximated the evolution of the performance over various ages are coherent with previous studies about motor control development and physiological decline. The proposed solution, i.e. serious games rehabilitation exercises coupled to motion analysis, seems to be an interesting tool to assess global motor function. Further studies are needed to study the influence of pathologies on the studied parameters.

Treadmill interventions in children under six years of age at risk of neuromotor delay

BACKGROUND

Delayed motor development may occur in children with Down syndrome, cerebral palsy, general developmental delay or children born preterm. It limits the child's exploration of the environment and can hinder cognitive and social-emotional development. Literature suggests that task-specific training, such as locomotor treadmill training, facilitates motor development.

OBJECTIVES

To assess the effectiveness of treadmill interventions on locomotor development in children with delayed ambulation or in pre-ambulatory children (or both), who are under six years of age and who are at risk for neuromotor delay.

SEARCH METHODS

In May 2017, we searched CENTRAL, MEDLINE, Embase, six other databases and a number of trials registers. We also searched the reference lists of relevant studies and systematic reviews.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs that evaluated the effect of treadmill intervention in the target population.

DATA COLLECTION AND ANALYSIS

Four authors independently extracted the data. Outcome parameters were structured according to the International Classification of Functioning, Disability and Health model.

MAIN RESULTS

This is an update of a Cochrane review from 2011, which included five trials. This update includes seven studies on treadmill intervention in 175 children: 104 were allocated to treadmill groups, and 71 were controls. The studies varied in population (children with Down syndrome, cerebral palsy, developmental delay or at moderate risk for neuromotor delay); comparison type (treadmill versus no treadmill; treadmill with versus without orthoses; high- versus low-intensity training); study duration, and assessed outcomes. Due to the diversity of the studies, only data from five studies were used in meta-analyses for five outcomes: age of independent walking onset, overall gross motor function, gross motor function related to standing and walking, and gait velocity. GRADE assessments of quality of the evidence ranged from high to very low.The effects of treadmill intervention on independent walking onset compared to no treadmill intervention was population dependent, but showed no overall effect (mean difference (MD) -2.08, 95% confidence intervals (CI) -5.38 to 1.22, 2 studies, 58 children; moderate-quality evidence): 30 children with Down syndrome benefited from treadmill training (MD -4.00, 95% CI -6.96 to -1.04), but 28 children at moderate risk of developmental delay did not (MD -0.60, 95% CI -2.34 to 1.14). We found no evidence regarding walking onset in two studies that compared treadmill intervention with and without orthotics in 17 children (MD 0.10, 95% CI -5.96 to 6.16), and high- versus low-intensity treadmill interventions in 30 children with Down syndrome (MD -2.13, 95% -4.96 to 0.70).Treadmill intervention did not improve overall gross motor function (MD 0.88, 95% CI -4.54 to 6.30, 2 studies, 36 children; moderate-quality evidence) or gross motor skills related to standing (MD 5.41, 95% CI -1.64 to 12.43, 2 studies, 32 children; low-quality evidence), and had a negligible improvement in gross motor skills related to walking (MD 4.51, 95% CI 0.29 to 8.73, 2 studies, 32 children; low-quality evidence). It led to improved walking skills in 20 ambulatory children with developmental delay (MD 7.60, 95% CI 0.88 to 14.32, 1 study) and favourable gross motor skills in 12 children with cerebral palsy (MD 8.00, 95% CI 3.18 to 12.82). A study which compared treadmill intervention with and without orthotics in 17 children with Down syndrome suggested that adding orthotics might hinder overall gross motor progress (MD -8.40, 95% CI -14.55 to -2.25).Overall, treadmill intervention showed a very small increase in walking speed compared to no treadmill intervention (MD 0.23, 95% CI 0.08 to 0.37, 2 studies, 32 children; high-quality evidence). Treadmill intervention increased walking speed in 20 ambulatory children with developmental delay (MD 0.25, 95% CI 0.08 to 0.42), but not in 12 children with cerebral palsy (MD 0.18, 95% CI -0.09 to 0.45).

AUTHORS' CONCLUSIONS

This update of the review from 2011 provides additional evidence of the efficacy of treadmill intervention for certain groups of children up to six years of age, but power to find significant results still remains limited. The current findings indicate that treadmill intervention may accelerate the development of independent walking in children with Down syndrome and may accelerate motor skill attainment in children with cerebral palsy and general developmental delay. Future research should first confirm these findings with larger and better designed studies, especially for infants with cerebral palsy and developmental delay. Once efficacy is established, research should examine the optimal dosage of treadmill intervention in these populations.

Neuroplasticity: Insights from Patients Harboring Gliomas

Neuroplasticity is the ability of the brain to reorganize itself during normal development and in response to illness. Recent advances in neuroimaging and direct cortical stimulation in human subjects have given neuroscientists a window into the timing and functional anatomy of brain networks underlying this dynamic process. This review will discuss the current knowledge about the mechanisms underlying neuroplasticity, with a particular emphasis on reorganization following CNS pathology. First, traditional mechanisms of neuroplasticity, most relevant to learning and memory, will be addressed, followed by a review of adaptive mechanisms in response to pathology, particularly the recruitment of perilesional cortical regions and unmasking of latent connections. Next, we discuss the utility and limitations of various investigative techniques, such as direct electrocortical stimulation (DES), functional magnetic resonance imaging (fMRI), corticocortical evoked potential (CCEP), and diffusion tensor imaging (DTI). Finally, the clinical utility of these results will be highlighted as well as possible future studies aimed at better understanding of the plastic potential of the brain with the ultimate goal of improving quality of life for patients with neurologic injury.

Serotonergic activation of locomotor behavior and posture in one-day old rats

The purpose of this study was to determine what dose of quipazine, a serotonergic agonist, facilitates air-stepping and induces postural control and patterns of locomotion in newborn rats. Subjects in both experiments were 1-day-old rat pups. In Experiment 1, pups were restrained and tested for air-stepping in a 35-min test session. Immediately following a 5-min baseline, pups were treated with quipazine (1.0, 3.0, or 10.0 mg/kg) or saline (vehicle control), administered intraperitoneally in a 50 μL injection. Bilateral alternating stepping occurred most frequently following treatment with 10.0 mg/kg quipazine, however the percentage of alternating steps, interlimb phase, and step period were very similar between the 3.0 and 10.0 mg/kg doses. For interlimb phase, the forelimbs and hindlimbs maintained a near perfect anti-phase pattern of coordination, with step period averaging about 1s. In Experiment 2, pups were treated with 3.0 or 10.0 mg/kg quipazine or saline, and then were placed on a surface (open field, unrestrained). Both doses of quipazine resulted in developmentally advanced postural control and locomotor patterns, including head elevation, postural stances, pivoting, crawling, and a few instances of quadrupedal walking. The 3.0 mg/kg dose of quipazine was the most effective at evoking sustained locomotion. Between the 2 experiments, behavior exhibited by the rat pup varied based on testing environment, emphasizing the role that environment and sensory cues exert over motor behavior. Overall, quipazine administered at a dose of 3.0 mg/kg was highly effective at promoting alternating limb coordination and inducing locomotor activity in both testing environments.

Spinal mediation of motor learning and memory in the rat fetus

Fetal rats can alter patterns of interlimb coordination after experience with a yoke that links two legs together. Yoke training results in a pronounced increase in conjugate limb movements (CLM). To determine whether yoke motor learning is mediated by spinal cord circuitry, fetal subjects at embryonic Day 20 (E20) received yoke training after mid-thoracic spinal cord transection or sham surgery. Both spinal and sham-treated fetuses exhibited an increase in CLM during training. In a second experiment, fetuses received initial yoke training, then were transected or sham treated before a 2nd training. Spinal and sham fetuses that were yoked during both training sessions exhibited a more rapid rise in CLM than those yoked only in the later session. These findings indicate that motor learning in fetal rats can be supported by spinal cord circuitry alone, and that savings implies a form of motor memory localized in the spinal cord.