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Afferent and efferent control of stance and gait: developmental changes in children
Insights
As children develop, their nervous systems mature, refining muscle responses to balance challenges. By age 6-10, children gain adult-like control over leg muscle reflexes during walking and standing.
Area of Science:
- Neuroscience
- Developmental Biology
- Motor Control
Background:
- The development of motor control involves complex changes in neural pathways.
- Understanding reflex system maturation is crucial for assessing normal motor development in children.
Purpose of the Study:
- To investigate the developmental trajectory of cerebral potentials (CPs) and electromyography (EMG) responses to perturbations in children aged 1-10 years.
- To compare reflex responses during standing versus gait across different age groups.
Main Methods:
- Electrophysiological recordings of CPs and leg muscle EMG.
- Application of perturbation impulses during stance and gait tasks.
- Analysis of responses in children aged 1-10 years.
Main Results:
- Youngest children (1-2 years) exhibited monosynaptic stretch reflexes and less developed EMG responses.
- Children aged 6-10 years displayed an adult-like pattern with suppressed monosynaptic reflexes and altered CPs during gait perturbations.
- A progressive increase in polysynaptic EMG responses and CP changes were observed in children aged 2-6 years.
Conclusions:
- Maturation of motor control involves the development of descending inhibition of afferent pathways and facilitation of polysynaptic reflexes.
- The ability to control afferent information during perturbations is established progressively during childhood.
- These findings highlight the age-dependent maturation of the nervous system's role in maintaining balance.
Abstract:
Comparisons were made between the cerebral potentials (CPs) and EMG responses of leg muscles evoked by perturbation impulses during stance and gait in normal children aged from 1 to 10 years. Changes in the efferent arm of the reflex systems during development were reflected in parallel changes with age of the afferent system, expressed in the CP: in the youngest children (1-2 years of age) monosynaptic stretch reflex potentials appeared following perturbations during both stance and gait, together with a reduced level of longer latency EMG responses. The CP, too, had a profile that did not, at this early stage, differ in either condition. In children from 6 to 10 years of age, the adult pattern was reached, with the suppression of monosynaptic stretch reflexes and the early part of the CP during gait perturbation. This is interpreted as an inhibition of group I afferents at both segmental and supraspinal levels, involving suppression of both segmental stretch reflexes and group I signals to supraspinal centres. This control of afferent information had yet to be established in early infancy. The age group from 2 to 6 years showed progressive changes, with an increase in both the level and phasic nature of polysynaptic EMG responses and a corresponding transformation of the latency and shape of the CP. It is suggested that maturation of compensatory EMG responses during gait is achieved by the establishment of descending inhibition of group I afferents and facilitation of polysynaptic spinal reflexes via group II afferents.