Development Of Motor System Research Articles

Segmental Diffusion Properties of the Corticospinal Tract and Motor Outcome in Hemiparetic Children With Perinatal Stroke.

Perinatal stroke injures developing motor systems, resulting in hemiparetic cerebral palsy. Diffusion tensor imaging can explore structural connectivity. We used diffusion tensor imaging to assess corticospinal tract diffusion in hemiparetic children with perinatal stroke. Twenty-eight children (6-18 years) with unilateral stroke underwent diffusion tensor imaging. Four corticospinal tract assessments included full tract, partial tract, minitract and region of interest. Diffusion characteristics (fractional anisotropy, mean, axial, and radial diffusivity) were calculated. Ratios (lesioned/nonlesioned) were compared across segments and to validated long-term motor outcomes (Pediatric Stroke Outcome Measure, Assisting Hand Assessment, Melbourne Assessment). Fractional anisotropy and radial diffusivity ratios decreased as tract size decreased, while mean diffusivity showed consistent symmetry. Poor motor outcomes were associated with lower fractional anisotropy in all segments and radial diffusivity correlated with both Assisting Hand Assessment and Melbourne Assessment. Diffusion imaging of segmented corticospinal tracts is feasible in hemiparetic children with perinatal stroke. Correlations with disability support clinical relevance and utility in model development for personalized rehabilitation.

A novel role for the DNA repair gene Rad51 in Netrin-1 signalling

Mutations in RAD51 have recently been linked to human Congenital Mirror Movements (CMM), a developmental disorder of the motor system. The only gene previously linked to CMM encodes the Netrin-1 receptor DCC, which is important for formation of corticospinal and callosal axon tracts. Thus, we hypothesised that Rad51 has a novel role in Netrin-1-mediated axon development. In mouse primary motor cortex neurons, Rad51 protein was redistributed distally down the axon in response to Netrin-1, further suggesting a functional link between the two. We next manipulated Rad51 expression, and assessed Netrin-1 responsiveness. Rad51 siRNA knockdown exaggerated Netrin-1-mediated neurite branching and filopodia formation. RAD51 overexpression inhibited these responses, whereas overexpression of the CMM-linked R250Q mutation, a predicted loss-of-function, had no effect. Thus, Rad51 appears to negatively regulate Netrin-1 signalling. Finally, we examined whether Rad51 might operate by modulating the expression of the Unc5 family, known negative regulators of Netrin-1-responsiveness. Unc5b and Unc5c transcripts were downregulated in response to Rad51 knockdown, and upregulated with RAD51 overexpression, but not R250Q. Thus, Rad51 negatively regulates Netrin-1 signalling, at least in part, by modulating the expression of Unc5s. Imbalance of positive and negative influences is likely to lead to aberrant motor system development resulting in CMMs.

Congenital Cranial Dysinnervation Disorders: A Literature Review

ABSTRACTCongenital cranial dysinnervation disorders (CCDD) is a new term describing a collection of non-progressive neurogenic syndromes. Initially referred to as congenital fibrosis syndrome, it was thought that the primary problem was extraocular muscular maldevelopment. Recent advancements in genetics and neuro-radiology have now determined the initial observation of fibrotic muscles is secondary to a primary lack of innervation from deficient, absent, or misguided cranial nerves. This presentation provides an overview of the known genes and phenotypes currently recognized within the CCDD domain. It will also highlight areas of current research being done in the area of cranial nerve development. Increased knowledge and awareness of these disorders has resulted in more research being conducted. These studies have provided a more complete understanding of efferent motor system development and are leading to improved treatment strategies for patients.

Congenital Cranial Dysinnervation Disorders: A Literature Review

Congenital cranial dysinnervation disorders (CCDD) is a new term describing a collection of non-progressive neurogenic syndromes. Initially referred to as congenital fibrosis syndrome, it was thought that the primary problem was extraocular muscular maldevelopment. Recent advancements in genetics and neuro-radiology have now determined the initial observation of fibrotic muscles is secondary to a primary lack of innervation from deficient, absent, or misguided cranial nerves. This presentation provides an overview of the known genes and phenotypes currently recognized within the CCDD domain. It will also highlight areas of current research being done in the area of cranial nerve development. Increased knowledge and awareness of these disorders has resulted in more research being conducted. These studies have provided a more complete understanding of efferent motor system development and are leading to improved treatment strategies for patients.

Analysis of thermal performance of an outer-rotor Surface-mounted permanent magnet (SPM) motor for electric vehicles

In this work, the heat distributions and maximum temperature variations of the rotor and stator in a SPM (Surface-mounted permanent magnet) motor were analyzed under different ambient temperatures (Tamb) and current densities (J). To achieve this, the conduction heat transfer between each of the motor components, the forced convection heat transfer inside the motor, and natural convection heat transfer between the inside of the motor and outside air were considered under steady state flow conditions. At the same time, copper loss and core loss, which are the representative motor losses, were also considered to simulate the heat generation inside the motor. To improve simulation accuracy and save time, only one-ninth part of the motor was investigated, using Finite element analysis (FEA). From these results, the operating limit temperature and current density conditions of the SPM motor were studied. It was revealed that the temperature inside the motor increased linearly as the current density increased due to the effects of stack length and core loss, and the cooling effect of the air gap was observed in most cases. At the same time, limit ranges for the stable operation of the SPM motor were suggested under various current densities (J) and ambient temperatures (Tamb). These results can be used as a database for the development of EV motor systems.

Environmental enrichment mitigates the impact of ancestral stress on motor skill and corticospinal tract plasticity

BackgroundAn adverse fetal environment in utero has been associated with long-term alterations in brain structure and function, and a higher risk of neurological disorders in later life. A common consequence of early adverse experience is impaired motor system function. A causal relationship for stress-associated impairments and a suitable therapy, however, have not been determined yet. ObjectiveTo investigate the impact of ancestral stress on corticospinal tract (CST) morphology and fine motor performance in rats, and to determine if adverse programming by ancestral stress can be mitigated by environmental enrichment therapy in rats. MethodsThe study examined F3 offspring generated by three lineages; one with prenatal stress only in the F1 generation, one with compounding effects of multigenerational prenatal stress, and a non-stress control lineage. F3 offspring from each lineage were injected with biotinylated dextran amine (BDA) into the motor cortex for anterograde tracing of the CST. ResultsExamination of the CST revealed reduced axonal density in the ancestrally stressed lineages. These anatomical changes were associated with significant impairments in skilled walking, as indicated by reduced foot placement accuracy and disturbed inter-limb coordination. Therapeutic intervention by environmental enrichment reduced the neuromorphological consequences of ancestral stress and restored skilled walking ability. ConclusionsThe data suggest a causal relationship between stress-induced abnormal CST function and loss of fine motor performance. Thus, ancestral stress may be a determinant of motor system development and motor skill. Environmental enrichment may represent an effective intervention for the adverse programming by ancestral stress and trauma.

Heterochronic neuromuscular junction development in an Australian marsupial (Macropus fuliginosus)

AbstractThe neuromuscular junction (NMJ) provides a connection between the somatic nervous and muscular systems. The present work documents, for the first time, the mature form of the NMJ in an Australian marsupial, the western gray kangaroo Macropus fuliginosus. Marsupials give birth to highly altricial young and the majority of motor system development thus occurs postnatally. We demonstrate that NMJ formation in the forelimbs of kangaroos precedes that in hindlimbs by several weeks, consistent with evidence of precocial forelimb development from other indices of motor system maturation in marsupials. Forelimb and hindlimb NMJs reach a similar level of development by the end of the first postnatal month, an outcome that results from accelerated hindlimb development in the early postnatal period together with a more unexpected stagnation or even regression of forelimb NMJ maturity over the same period. This study suggests that the pattern of NMJ maturation may be adjusted in forelimb as opposed to hindlimb. Elucidation of the underlying cellular control mechanisms may inform current understanding of NMJ formation, and as such the broader processes involved in synaptic formation.

Electrical maturation of spinal neurons in the human fetus: comparison of ventral and dorsal horn.

The spinal cord is critical for modifying and relaying sensory information to, and motor commands from, higher centers in the central nervous system to initiate and maintain contextually relevant locomotor responses. Our understanding of how spinal sensorimotor circuits are established during in utero development is based largely on studies in rodents. In contrast, there is little functional data on the development of sensory and motor systems in humans. Here, we use patch-clamp electrophysiology to examine the development of neuronal excitability in human fetal spinal cords (10-18 wk gestation; WG). Transverse spinal cord slices (300 μm thick) were prepared, and recordings were made, from visualized neurons in either the ventral (VH) or dorsal horn (DH) at 32°C. Action potentials (APs) could be elicited in VH neurons throughout the period examined, but only after 16 WG in DH neurons. At this age, VH neurons discharged multiple APs, whereas most DH neurons discharged single APs. In addition, at 16-18 WG, VH neurons also displayed larger AP and after-hyperpolarization amplitudes than DH neurons. Between 10 and 18 WG, the intrinsic properties of VH neurons changed markedly, with input resistance decreasing and AP and after-hyperpolarization amplitudes increasing. These findings are consistent with the hypothesis that VH motor circuitry matures more rapidly than the DH circuits that are involved in processing tactile and nociceptive information.

Sensorimotor dysfunctions as primary features of autism spectrum disorders.

Motor impairments in autism spectrum disorders (ASD) have received far less research attention than core social-communication and cognitive features. Yet, behavioral, neurophysiological, neuroimaging and histopathological studies have documented abnormal motor system development in the majority of individuals with ASD suggesting that these deficits may be primary to the disorder. There are several unique advantages to studying motor development in ASD. First, the neurophysiological substrates of motor skills have been well-characterized via animal and human lesion studies. Second, many of the single-gene disorders associated with ASD also are characterized by motor dysfunctions. Third, recent evidence suggests that the onset of motor dysfunctions may precede the emergence of social and communication deficits during the first year of life in ASD. Motor deficits documented in ASD indicate disruptions throughout the neuroaxis affecting cortex, striatum, the cerebellum and brainstem. Questions remain regarding the timing and development of motor system alterations in ASD, their association with defining clinical features, and their potential for parsing heterogeneity in ASD. Pursuing these questions through neurobiologically informed translational research holds great promise for identifying gene-brain pathways associated with ASD.

Developmental plasticity of coordinated action patterns in the perinatal rat.

Some of the most simple, stereotyped, reflexive, and spinal-mediated motor behaviors expressed by animals display a level of flexibility and plasticity that is not always recognized. We discuss several examples of how coordinated action patterns have been shown to be flexible and adaptive in response to sensory feedback. We focus on interlimb and intralimb coordination during the expression of two action patterns (stepping and the leg extension response) in newborn rats, as well as interlimb motor learning. We also discuss the idea that the spinal cord is a major site for supporting plasticity in the developing motor system. An implication of this research is that normally occurring sensory stimulation during the perinatal period influences the typical development and expression of action patterns, and that exploiting the developmental plasticity of the motor system may lead to improved strategies for promoting recovery of function in human infants with motor disorders.

Early intervention to improve hand function in hemiplegic cerebral palsy.

Children with hemiplegic cerebral palsy often have marked hand involvement with excessive thumb adduction and flexion and limited active wrist extension from infancy. Post-lesional aberrant plasticity can lead to progressive abnormalities of the developing motor system. Disturbances of somatosensory and visual function and developmental disregard contribute to difficulties with hand use. Progressive soft tissue and bony changes may occur, leading to contractures, which further limit function in a vicious cycle. Early intervention might help to break this cycle, however, the precise nature and appropriateness of the intervention must be carefully considered. Traditional approaches to the hemiplegic upper limb include medications and botulinum toxin injections to manage abnormalities of tone, and surgical interventions. Therapist input, including provision of orthoses, remains a mainstay although many therapies have not been well evaluated. There has been a recent increase in interventions for the hemiplegic upper limb, mostly aimed outside the period of infancy. These include trials of constraint-induced movement therapy (CIMT) and bimanual therapy as well as the use of virtual reality and robot-assisted therapy. In future, non-invasive brain stimulation may be combined with therapy. Interventions under investigation in the infant age group include modified CIMT and action observation therapy. A further approach which may be suited to the infant with thumb-in-palm deformity, but which requires evaluation, is the use of elastic taping. Enhanced cutaneous feedback through mechanical stimulation to the skin provided by the tape during movement has been postulated to modulate ongoing muscle activity. If effective, this would represent a low-cost, safe, widely applicable early intervention.

Husbandry of Spanish ribbed newts (Pleurodeles waltl).

Research on urodele amphibians, such as newts, is constantly contributing to our understanding of fundamental biological processes. In the present chapter, we present detailed husbandry protocols for the Spanish ribbed newt (Pleurodeles waltl ). We describe the main phases of their life cycle, with emphasis on the progressive development of sensory, motor, and integration systems, which lead to the acquisition of specific stereotyped (and conditioned) behaviors. The methods are outlined to manage housing, feeding, handling, captive breeding, health monitoring, and euthanasia in this species under laboratory conditions. With minor changes, these protocols can also be applied to other species of urodele amphibians commonly used in laboratory research.

Analysis of Development and Application of In-Wheel Motor System for Electric Vehicle

In-wheel motor driving electric vehicle is an important development direction in the future. Aiming at the in-wheel motor used for electric vehicle, a comprehensive analysis of its present design and application situation was made, then the performance characteristics of in-wheel motor driven electric vehicle was proposed. Moreover, the concept and structure of in-wheel motor system were stated, and the current development situation of its each part was expounded. Finally, on the basis of analysis of the positive and negative effects on the performance of electric vehicle, the key technical problems concerning in-wheel motor system design and the solutions were summed up.

Improvements in hand function after intensive bimanual training are not associated with corticospinal tract dysgenesis in children with unilateral cerebral palsy

Unilateral cerebral palsy (CP) results from damage to the developing brain that occurs within the first 2 years of life. Previous studies found associations between asymmetry in the size of the corticospinal tract (CST) from the two hemispheres and severity of hand impairments in children with unilateral CP. The extent to which CST damage affects the capacity for hand function improvement is unknown. This study examines the association between an estimate of CST dysgenesis and (1) hand function and (2) the efficacy of intensive bimanual training in improving hand function. Children with unilateral CP, age 3.6–14.9 years, n = 35, received intensive bimanual training. Children engaged in bimanual functional/play activities (6 h/day, 15 days). Peduncle asymmetry, an estimate of CST dysgenesis, was measured on T1-weighted magnetic resonance imaging scans. Hand function was measured pre- and post-treatment using the assisting hand assessment (AHA) and Jebsen–Taylor test of hand function (JTTHF). AHA and JTTHF improved post-treatment (p < 0.001). Peduncle asymmetry was correlated with baseline AHA and JTTHF (p < 0.001) but not with AHA or JTTHF improvement post-training (R 2 < 0.1, p > 0.2). An estimate of CST dysgenesis is correlated with baseline hand function but is a poor predictor of training efficacy, possibly indicating a flexibility of developing motor systems to mediate recovery.

The Winding Insulation Electro-Thermal Aging Model of Electric Vehicle Motor Based on Operation States

Electric vehicle (EV) motor and common traction motor are operation in different states, the insulation aging model based fixed working conditions are no longer applicable. The secondary development of motor system is carried in ADVISOR to get a new motor thermal model with which to analysis the lifetime of winding insulation. In addition, SIMULINK model is established to decouple motor currents in ADVISOR. ANSYS is carried to simulate the motor temperature rise using the obtained decouple currents, two results of models are in good agreement which verifies the validity of the redevelopment thermal model. Combined with the electric ageing model of winding insulation, the electro-thermal aging model in the EV motor is proposed based actual operation states, and insulation lifetime is calculated which provides theory basis for the analysis of electro-thermal aging model in EV motors.

Development of Motor and Controller's Engineering Measurement System

As energy crisis, the ship with electric propulsion has been the mainstream development and application trends of shipping industry and the world's navies in the present world. In order to develop domestic marine electric propulsion system, the test platform of marine electric propulsion system which can simulate the ship operating condition is constructed; the physical simulation of ship load is realized; the no-load, loading and overloading test for motors are completed. In addition, the platform can also be used to do the test for onshore equipments-the construction machinery such as electric forklift. Finally, there is no similar production in the domestic by far.

Predictions in the light of your own action repertoire as a general computational principle

We argue that brains generate predictions only within the constraints of the action repertoire. This makes the computational complexity tractable and fosters a step-by-step parallel development of sensory and motor systems. Hence, it is more of a benefit than a literal constraint and may serve as a universal normative principle to understand sensorimotor coupling and interactions with the world.

An fMRI Compatible Wrist Robotic Interface to Study Brain Development in Neonates

A comprehensive understanding of the mechanisms that underlie brain development in premature infants and newborns is crucial for the identification of interventional therapies and rehabilitative strategies. fMRI has the potential to identify such mechanisms, but standard techniques used in adults cannot be implemented in infant studies in a straightforward manner. We have developed an MR safe wrist stimulating robot to systematically investigate the functional brain activity related to both spontaneous and induced wrist movements in premature babies using fMRI. We present the technical aspects of this development and the results of validation experiments. Using the device, the cortical activity associated with both active and passive finger movements were reliably identified in a healthy adult subject. In two preterm infants, passive wrist movements induced a well localized positive BOLD response in the contralateral somatosensory cortex. Furthermore, in a single preterm infant, spontaneous wrist movements were found to be associated with an adjacent cluster of activity, at the level of the infant's primary motor cortex. The described device will allow detailed and objective fMRI studies of somatosensory and motor system development during early human life and following neonatal brain injury.

Foresight Scenario Analysis of Motor System of Electric Vehicle

In order to describe the trend of motor system development of electric vehicle and to figure out the factors that would affect the external drives and the internal resources, the thesis uses scenario analysis method to be the basic framework, adding modified Delphi method to clarify time transition into five categories: changeless, changeable, disappeared, uncertain states and newborn. More precisely, the five factors is used to construct “Scenario Analysis of Markov Modified Delphi Method”. The thesis focuses on motor system to do the Foresight analysis, using the transition concept of Markov Chain to clarify the key factors of uncertain states into motor system: brushless DC (BLDC) motor, surface permanent magnet synchronous motor and Switched Reluctance In-Wheel Motor. Moreover, the changeless concept of Markov Chain is used to be background, adding the key factors of changeable and uncertain states to clarify seven kinds of scenario portfolio: basic scenario, scenario assumption I, scenario assumption II, future scenario, breakthrough scenario I, breakthrough scenario II and challenge scenario. It could make the government, industries and related departments realize the development trend of key components about electric vehicle by the scenario descriptions. It can increase their willingness to invest in the related researches to achieve future image, also shape the usable engineering technique and integrated system concepts of electric vehicles in 2020 for public.

The Zebrafish Homologue of the Human DYT1 Dystonia Gene Is Widely Expressed in CNS Neurons but Non-Essential for Early Motor System Development

DYT1 dystonia is caused by mutation of the TOR1A gene, resulting in the loss of a single glutamic acid residue near the carboxyl terminal of TorsinA. The neuronal functions perturbed by TorsinA[ΔE] are a major unresolved issue in understanding the pathophysiology of dystonia, presenting a critical roadblock to developing effective treatments. We identified and characterized the zebrafish homologue of TOR1A, as a first step towards elucidating the functions of TorsinA in neurons, in vivo, using the genetically-manipulable zebrafish model. The zebrafish genome was found to contain a single alternatively-spliced tor1 gene, derived from a common ancestral locus shared with the dual TOR1A and TOR1B paralogues found in tertrapods. tor1 was expressed ubiquitously during early embryonic development and in multiple adult tissues, including the CNS. The 2.1 kb tor1 mRNA encodes Torsin1, which is 59% identical and 78% homologous to human TorsinA. Torsin1 was expressed as major 45 kDa and minor 47 kDa glycoproteins, within the cytoplasm of neurons and neuropil throughout the CNS. Similar to previous findings relating to human TorsinA, mutations of the ATP hydrolysis domain of Torsin1 resulted in relocalization of the protein in cultured cells from the endoplasmic reticulum to the nuclear envelope. Zebrafish embryos lacking tor1 during early development did not show impaired viability, overt morphological abnormalities, alterations in motor behavior, or developmental defects in the dopaminergic system. Torsin1 is thus non-essential for early development of the motor system, suggesting that important CNS functions may occur later in development, consistent with the critical time window in late childhood when dystonia symptoms usually emerge in DYT1 patients. The similarities between Torsin1 and human TorsinA in domain organization, expression pattern, and cellular localization suggest that the zebrafish will provide a useful model to understand the neuronal functions of Torsins in vivo.