Developmental milestones in toddlers with atypical development

Motor development of stable born healthy foals during the first 24 hours

The motor development of 14 healthy foals was observed using continuous video-recording from birth to 24 h of age. An ethogram was made of behaviours of interest with behaviour quantification using CowLog software. Behaviours were divided into six main classes: main activities, attempts to get up or lie down, nursing, playing and other skills, being helped by a human, and the foal not being visible. First-time behaviours (mean, range) of early motor development after birth included going into sternal position (5.4 min, 0-34.5 min), attempting to get up (7.6 min, 0.5-34.6 min), successfully getting up (56.4 min, 27.7 min - 1 h 43.3 min), walking (1 h 1.9 min, 28.1 min - 1 h 43.4 min), nursing (1 h 49.1 min, 1 h 10.3 min - 2 h 29.7 min), shaking (31.9 min, 0.2 min - 2 h 32.7 min), running (2 h 55.6 min, 1h 33.2 min - 6 h 12.1 min), walking backwards (4 h 12.8 min, 56.9 min - 12 h 50.6 min), frolicking (4 h 52.5 min, 2 h 3 min - 15 h 18.8 min), and autogrooming (7 h 30.3 min, 43.3 min - 14 h 40.1 min). All foals made several attempts before they were able to get up for the first time (61.9, 14-103). During the first 24 h the overall duration of lying down was highest, followed by standing and walking. This information adds to the basic information for assessing normal motor development in these animals, with the potential to identify delayed development.

Reduced corticospinal drive to antagonist muscles of upper and lower limbs during hands-and-knees crawling in infants with cerebral palsy: Evidence from intermuscular EMG-EMG coherence

BACKGROUND

There is growing interest in understanding the central control of hands-and-knees crawling, especially as a significant motor developmental milestone for early assessment of motor dysfunction in infants with cerebral palsy (CP) who have not yet acquired walking ability. In particular, CP is known to be associated with walking dysfunctions caused by early damage and incomplete maturation of the corticospinal tract. However, the extent of damage to the corticospinal connections during crawling in infants with CP has not been fully clarified. Therefore, this study aimed to investigate the disparities in intermuscular EMG-EMG coherence, which serve as indicators of corticospinal drives to antagonist muscles in the upper and lower limbs during crawling, between infants with and without CP.

METHODS

This study involved 15 infants diagnosed with CP and 20 typically developing (TD) infants. Surface EMG recordings were obtained from two pairs of antagonist muscles in the upper limbs (triceps brachii (TB) and biceps brachii (BB)) and lower limbs (quadriceps femoris (QF) and hamstrings (HS)), while the infants performed hands-and-knees crawling at their self-selected velocity. Intermuscular EMG-EMG coherence was computed in two frequency bands, the beta band (15-30 Hz) and gamma band (30-60 Hz), which indicate corticospinal drive. Additionally, spatiotemporal parameters, including crawling velocity, cadence, duration, and the percentage of stance phase time, were calculated for comparison. Spearman rank correlations were conducted to assess the relationship between EMG-EMG coherence and crawling spatiotemporal parameters.

RESULTS

Infants with CP exhibited significantly reduced crawling velocity, decreased cadence, longer cycle duration, and a higher percentage of stance phase time compared to TD infants. Furthermore, CP infants demonstrated decreased coherence in the beta and gamma frequency bands (indicators of corticospinal drive) in both upper and lower limb muscles. Regarding limb-related differences in the beta and gamma coherence, significant disparities were found between upper and lower limb muscles in TD infants (p < 0.05), but not in infants with CP (p > 0.05). Additionally, significant correlations between coherence metrics and crawling spatiotemporal parameters were identified in the TD group (p < 0.05), while such correlations were not evident in the CP group.

CONCLUSIONS

Our findings suggest that the corticospinal drive may functionally influence the central control of antagonist muscles in the limbs during typical infant crawling. This functional role could be impaired by neurological conditions such as cerebral palsy. The neurophysiological markers of corticospinal drive, specifically intermuscular EMG-EMG coherence during crawling in infants with cerebral palsy, could potentially serve as a tool to assess developmental response to therapy.

Parenting in Cerebral Palsy: Understanding the Perceived Challenges and Needs Faced by Parents of Elementary School Children

Cerebral palsy (CP) can be considered the most frequent childhood physical disorder. The severity and type of dysfunction depend on the brain injury. Movement and posture are the most affected areas. CP is a lifelong condition, and parenting a child with this disorder brings additional challenges (e.g., dealing with grief) and needs (e.g., information). Identifying and characterizing their challenges and needs are pivotal to enrich the knowledge in this field and help draw more suitable support for parents. Interviews with 11 parents of children with CP attending elementary school were conducted. The discourse was transcribed, and a thematic analysis was performed. Three themes emerged from the data: (i) challenges of parenting a child with CP (e.g., internal challenges), (ii) crucial needs for parents to cope with a child with CP (e.g., information), and (iii) the intersection between challenges and needs of parents of children with CP (e.g., unawareness). Regarding the challenges and needs characterization, lifespan was the most frequent period of child development, and the microsystem was the context of life most reported. The findings may inform the design of educational and remediation interventions to support families of children with CP attending elementary school.

Effects of Early Motor Interventions on Gross Motor and Locomotor Development for Infants at-Risk of Motor Delay: A Systematic Review

Aim

To systematically examine the effect of early motor interventions on motor and locomotor development in infants <1 year of age with motor developmental disability or at risk of motor delay.

Methods

Pertinent literature from January 2000 to September 2021 was identified by searching the PubMed, Embase, Cochrane, Pedro and Web of Science databases. Selection criteria included interventions starting before 12 months corrected age. Methodological quality was assessed with AACPDM criteria, Mallen score and Cochrane risk of bias methodology. Evaluation procedure was performed using PRISMA protocol (PICO approach) and AMSTAR-2. This review was preregistered in PROSPERO (CRD42021286445).

Results

Ten articles met the inclusion criteria; seven had moderate to strong methodological quality. The interventions included treadmill training (n = 3), crawling training (n = 1), "tummy time" (n = 1), physical therapy with neonatal developmental program (n = 1) or Bobath approach (n = 1), treadmill training combined with active leg movements (n = 2) or Bobath physiotherapy (n = 1). The three key characteristics of effective interventions that emerged from the review were: (1) the infants' disability or risk of delay was well-defined; (2) the protocol was standardized and easy to replicate; (3) infants were required to make active movements.

Conclusion

There is an urgent need for additional high-quality studies on the effects of early motor interventions on the gross motor and locomotor development of infants with a range of disabilities or risks for delay. Suggestions for future research are outlined.

Promoting Participation in Physical Activity in Children and Adolescents With Down Syndrome

Children with Down syndrome (DS) often have lower physical activity (PA) levels compared with their peers with typical development, and face challenges to being physically active such as medical comorbidities, access issues, and societal stigma. Physical therapists are experts in exercise prescription and PA and are thus uniquely qualified to successfully promote participation in children with DS, in spite of inherent challenges. Our perspective is that a shift in physical therapy service delivery is needed. We suggest that physical therapists change the focus of their interventions for children with DS from underlying impairments such as low tone or joint laxity or from developing motor skills in isolation and "correct" movement patterns. Instead, physical therapists should allow the PA preferences and the environmental contexts of the children and adolescents they are working with to direct the treatment plan. In this way, physical therapist intervention becomes more child centered by concentrating on developing the specific skills and strategies required for success in the child's preferred PA. In this article, we consider the role of pediatric physical therapists in the United States, as well as in low- and middle-income countries, in promoting and monitoring PA in children with DS from infancy through adolescence. Examples of physical therapist interventions such as tummy time, movement exploration, treadmill training, bicycle riding, and strength training are discussed, across infancy, childhood, and adolescence, with a focus on how to successfully promote lifelong participation in PA.

LAY SUMMARY

Physical therapists are experts in exercise and physical activity and are thus uniquely qualified to promote participation in children with Down syndrome. Instead of focusing on impairments or "correct" movement patterns, physical therapists are encouraged to allow the child and the child's environment to direct the treatment plan.

Behavioral Phenotyping for Down Syndrome in Mice

Down syndrome (DS) is the most frequent genetic cause of intellectual disability, characterized by alterations in different behavioral symptom domains: neurodevelopment, motor behavior, and cognition. As mouse models have the potential to generate data regarding the neurological basis for the specific behavioral profile of DS, and may indicate pharmacological treatments with the potential to affect their behavioral phenotype, it is important to be able to assess disease-relevant behavioral traits in animal models in order to provide biological plausibility to the potential findings. The field is at a juncture that requires assessments that may effectively translate the findings acquired in mouse models to humans with DS. In this article, behavioral tests are described that are relevant to the domains affected in DS. A neurodevelopmental behavioral screen, the balance beam test, and the Multivariate Concentric Square Field test to assess multiple behavioral phenotypes and locomotion are described, discussing the ways to merge these findings to more fully understand cognitive strengths and weaknesses in this population. New directions for approaches to cognitive assessment in mice and humans are discussed. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Preweaning neurodevelopmental battery Basic Protocol 2: Balance beam Basic Protocol 3: Multivariate concentric square field test (MCSF).

Inter-Limb Muscle Synergy of Hands-and-Knees Crawling in Typical Developing Infants and Infants with Developmental Delay

The aim of this study was to quantify and compare the inter-limb muscle coordination during crawling between typically developing infants and infants with developmental delay. Typically developing (TD, $\text{N}=$20) infants and infants with at risk of developmental delay (ARDD, $\textbf{N}=$33) or confirmed developmental delayCDD, N=14) participated in this study. Surface electromyography of eight muscles from arms and legs and the corresponding joint kinematic data were collected while they were crawling on hands and knees at their self-selected velocity. The number of used inter-limb muscle synergies during crawling was identified by nonnegative matrix factorization algorithm. Our results showed that there was no significant difference in the number of used muscle synergies between ARDD and TD infants during crawling. However, a reduced number of synergies were identified in infants with CDD, as compared to that in TD and ARDD infants, indicating constrained neuromuscular control strategy during crawling in developmental delayed infants. The absence of inter-limb muscle synergies may be one of the mechanisms underlying the impairments of crawling in developmental delayed infants, who are at high risk of cerebral palsy. This result also suggests that the metrics of muscle synergy during infant crawling, such as the number of synergy, may be feasible as a biomarker for early diagnosis of infants with cerebral palsy.

Robot Reinforcement and Error-Based Movement Learning in Infants With and Without Cerebral Palsy

BACKGROUND

Prone mobility, central to development of diverse psychological and social processes that have lasting effects on life participation, is seldom attained by infants with cerebral palsy (CP) and has no tested interventions. Reinforcement learning (RL) and error-based movement learning (EBL) offer novel intervention possibilities.

OBJECTIVE

This study examined movement learning strategies in infants with or at risk for CP using RL and EBL during acquisition of prone locomotion.

DESIGN

The study was a randomized trial that used repeated measures.

SETTING

The study setting was a university physical therapy clinic in the United States.

PATIENTS

Thirty infants aged 4.5 to 6.5 months participated in the study: 24 had or were at risk for CP, and 6 were typically developing.

INTERVENTION

Infants with and at risk for CP were randomly assigned to a combination of RL and EBL (SIPPC-RE), or RL only (SIPPC-R) conditions. Infants with typical development comprised the RL-only reference group (SIPPC-TD). Infants trained in prone locomotion with the Self-Initiated Prone Progression Crawler (SIPPC) robotic system for three 5-minute trials, twice a week for 12 weeks in their homes or child care. All training sessions were videotaped for behavioral coding.

MEASUREMENTS

The SIPPC gathered robot and infant trunk/limb movement data. Randomized 2-way analysis of variance with repeated measures and Pearson r to analyze the data was used.

RESULTS

Results included the number of arm movements and trial-and-error activity distinguished between the SIPPC-RE and SIPPC-R groups. The mean change in arm movements from baseline for the SIPPC-RE and SIPPC-R groups was 4.8 m and -7.0 m, respectively. The mean differences in rotational amplitude (trial and error) from baseline to the end of the study were 278 degrees and 501 degrees, respectively. These changes were correlated with distance traveled and goal-directed movements. The latter increased over the 12 weeks for the SIPPC-RE and SIPPC-TD groups, but not the SIPPC-R group.

LIMITATIONS

The CP groups were unequal due to reassignment and did not include a typically developing comparison group of a combination of RL and EBL.

CONCLUSION

These findings suggest movement learning and retention in infants with CP is differentially affected by the use of RL and EBL, with a combination of both showing more promise than RL alone. The findings also implicate cognition, type of brain insult, emergence of reaching, and muscle force production, which must be explored in future studies.

Lifespan analysis of brain development, gene expression and behavioral phenotypes in the Ts1Cje, Ts65Dn and Dp(16)1/Yey mouse models of Down syndrome

Down syndrome (DS) results from triplication of human chromosome 21. Neuropathological hallmarks of DS include atypical central nervous system development that manifests prenatally and extends throughout life. As a result, individuals with DS exhibit cognitive and motor deficits, and have delays in achieving developmental milestones. To determine whether different mouse models of DS recapitulate the human prenatal and postnatal phenotypes, here, we directly compared brain histogenesis, gene expression and behavior over the lifespan of three cytogenetically distinct mouse models of DS: Ts1Cje, Ts65Dn and Dp(16)1/Yey. Histological data indicated that Ts65Dn mice were the most consistently affected with respect to somatic growth, neurogenesis and brain morphogenesis. Embryonic and adult gene expression results showed that Ts1Cje and Ts65Dn brains had considerably more differentially expressed (DEX) genes compared with Dp(16)1/Yey mice, despite the larger number of triplicated genes in the latter model. In addition, DEX genes showed little overlap in identity and chromosomal distribution in the three models, leading to dissimilarities in affected functional pathways. Perinatal and adult behavioral testing also highlighted differences among the models in their abilities to achieve various developmental milestones and perform hippocampal- and motor-based tasks. Interestingly, Dp(16)1/Yey mice showed no abnormalities in prenatal brain phenotypes, yet they manifested behavioral deficits starting at postnatal day 15 that continued through adulthood. In contrast, Ts1Cje mice showed mildly abnormal embryonic brain phenotypes, but only select behavioral deficits as neonates and adults. Altogether, our data showed widespread and unexpected fundamental differences in behavioral, gene expression and brain development phenotypes between these three mouse models. Our findings illustrate unique limitations of each model when studying aspects of brain development and function in DS. This work helps to inform model selection in future studies investigating how observed neurodevelopmental abnormalities arise, how they contribute to cognitive impairment, and when testing therapeutic molecules to ameliorate the intellectual disability associated with DS.This article has an associated First Person interview with the first author of the paper.

Absence of Prenatal Forebrain Defects in the Dp(16)1Yey/+ Mouse Model of Down Syndrome

Studies in humans with Down syndrome (DS) show that alterations in fetal brain development are followed by postnatal deficits in neuronal numbers, synaptic plasticity, and cognitive and motor function. This same progression is replicated in several mouse models of DS. Dp(16)1Yey/+ (hereafter called Dp16) is a recently developed mouse model of DS in which the entire region of mouse chromosome 16 that is homologous to human chromosome 21 has been triplicated. As such, Dp16 mice may more closely reproduce neurodevelopmental changes occurring in humans with DS. Here, we present the first comprehensive cellular and behavioral study of the Dp16 forebrain from embryonic to adult stages. Unexpectedly, our results demonstrate that Dp16 mice do not have prenatal brain defects previously reported in human fetal neocortex and in the developing forebrains of other mouse models, including microcephaly, reduced neurogenesis, and abnormal cell proliferation. Nevertheless, we found impairments in postnatal developmental milestones, fewer inhibitory forebrain neurons, and deficits in motor and cognitive performance in Dp16 mice. Therefore, although this new model does not express prenatal morphological phenotypes associated with DS, abnormalities in the postnatal period appear sufficient to produce significant cognitive deficits in Dp16.

How do researchers define self-injurious behavior?

Self-injurious behavior is commonly observed among persons with intellectual disabilities. However, a second parallel use of this term is used in the general mental health field for self-mutilation. The authors describe these two disorders and how they differ. Characteristics of what we refer to as repetitive self-injurious behavior among persons with intellectual disabilities and risk factors for these behaviors are discussed. We also describe different assessment/testing methods which aid in defining this phenomenon. The implications of these data for research and clinical practice are discussed.