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Published on: June 1, 2015
Developmental Changes of Muscle Synergies in an Infant's Walking
Insights
Primitive stepping in infants involves muscle coordination patterns. This study tracked these patterns using EMG, revealing changes before and after the reflex disappears, offering insights into early gait development.
Area of Science:
- Developmental neuroscience
- Motor control in infants
- Biomedical engineering
Background:
- Primitive stepping is an innate neonatal reflex.
- The developmental trajectory and functional significance of primitive stepping remain unclear.
- Understanding the transition from reflexive to voluntary movement is crucial for developmental research.
Purpose of the Study:
- To investigate the changes in muscle synergies during infant development.
- To explore the relationship between primitive stepping and the emergence of voluntary gait.
- To analyze the spatiotemporal coordination of muscle activity in infants aged 4-18 weeks.
Main Methods:
- Electromyography (EMG) data was collected from a single infant over 14 weeks.
- Non-negative matrix factorization (NMF) was employed to extract muscle synergies.
- Analysis focused on changes in synergy composition and activation timing.
Main Results:
- Significant alterations in muscle synergies were observed around the period of primitive stepping disappearance.
- Some muscle synergies retained their constituent muscles but exhibited modified activation timing.
- This suggests a neural reorganization underlying the transition from reflexive to voluntary locomotion.
Conclusions:
- Muscle synergies undergo significant adaptation during early infancy.
- These adaptations are linked to the developmental milestone of losing primitive stepping.
- The findings provide a novel perspective on the neural mechanisms governing the development of voluntary gait.
Abstract:
Primitive stepping is one of the primitive reflexes in newborns in response to external stimuli. It is known that primitive stepping disappears about two months after birth, but its role and the relationship with voluntary gait acquired later are still unknown. In this study, we extracted muscle synergies, spatiotemporal coordination patterns of muscle activities, from EMG measured in one infant during growth (4-18 weeks of age) using non-negative matrix factorization (NMF). We found that a synergy changed before and after the disappearance of the primitive stepping, and others maintained the recruited muscles but changed the onset timing of the activations.
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