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General movements in early infancy: what do they tell us about the nervous system?
Insights
Muscle coordination in general movements (GMs) evolves from writhing to fidgety in term infants. Preterm infants show distinct GMs, but differences resolve by fidgety age, unlike abnormal GMs indicating potential loss of control.
Area of Science:
- Neuroscience
- Developmental Biology
- Biomedical Engineering
Background:
- General movements (GMs) are spontaneous motor activities crucial for infant development.
- Understanding GM development aids in identifying neurological abnormalities early.
- Polymyography (polyEMG) combined with video analysis provides detailed insights into muscle activation patterns during GMs.
Observation:
- Normal full-term infants transition from slow, writhing GMs to more fluid, fidgety GMs around 2-3 months.
- Healthy preterm infants exhibit 'preterm' GMs with longer EMG burst durations and variable co-activation compared to full-term newborns.
- Longitudinal observation revealed differences in polyEMG patterns between preterm and full-term infants during writhing GMs, which disappeared by the fidgety stage.
Findings:
- The transformation of GMs in full-term infants correlates with decreased tonic background activity and reduced amplitude/duration of phasic EMG bursts.
- Preterm infants' GMs display unique characteristics, including longer EMG burst durations and greater variability in muscle co-activation.
- Abnormal GMs are potentially identified by synchronized muscle onset across extremities and 5-8 Hz EMG burst packaging, suggesting impaired supraspinal control.
Implications:
- These findings enhance our understanding of typical and atypical motor development in infants.
- The study provides potential biomarkers for early detection of neurological dysfunction in both preterm and full-term infants.
- Identifying specific EMG patterns associated with abnormal GMs could lead to targeted early interventions.
Abstract:
Developmental changes in muscle coordination patterns of normal and abnormal general movements (GMs) are described. GMs were studied simultaneously with video-recording and polymyography (polyEMG). GMs of normal full-term infants gradually lose their neonatally slow and 'writhing' character, to be turned into the elegant flow of small movements of 'fidgety' GMs at the age of 2-3 months. This transformation coincides with changes in the polyEMG. Tonic background activity decreases concurrent with a reduction in amplitude and duration of phasic bursts. The coordination between antagonistic muscles does not change, co-activation remains the prevailing pattern. Secondly, preliminary results on healthy preterms (n = 6) are presented. At the examination age of 33-34 weeks postmenstrual age the preterms showed so-called 'preterm' GMs, which are characterized by variation and graceful complexity. EMG burst duration was significantly longer during 'preterm' GMs than during 'writhing' GMs of full-term newborns. The percentage of co-activation during 'preterm' GMs varied considerably. The polyEMG of 'writhing' GMs of two preterms, who were followed longitudinally, differed from that of 'writhing' GMs of full-terms. At 'fidgety' age the EMG differences between preterms and full-terms had disappeared. Finally the first results on abnormal GMs are reported. A synchronized onset of muscle activity in all extremity muscles and 'packaging' of EMG-bursts into subunits of 5-8 Hz. seemed to be specific properties of these abnormal GMs. This could indicate a loss of supraspinal control.