Related Experiment Videos
Epigenetic development of postural responses for sitting during infancy
1Nobel Institute for Neurophysiology, Karolinska Institute, Stockholm, Sweden.
Insights
Infant postural responses develop predictably before independent sitting. Basic muscle activation patterns in infants resemble adults, but head movements differ, suggesting early development of postural control mechanisms.
Area of Science:
- Developmental neuroscience
- Motor control
- Biophysics
Background:
- Understanding the emergence of postural control in infants is crucial for developmental milestones.
- Postural responses in infants differ significantly from those in adults, necessitating detailed investigation.
Purpose of the Study:
- To investigate the developmental trajectory of postural responses in children before and during the acquisition of independent sitting.
- To compare infant postural responses to those observed in adults.
Main Methods:
- Electromyography (EMG) and kinematic analysis were used to record body movements and muscle activity in response to surface perturbations (translation and rotation).
- Children were categorized as either able to sit independently or not yet able to sit without support.
- Perturbations were applied in directions causing backward and forward body sway.
Main Results:
- Independently sitting children demonstrated consistent muscle activation patterns in ventral hip, trunk, and neck muscles, with inhibition of extensor muscles.
- Backward sway perturbations elicited predictable pelvic rotation as the initial movement, preceding irregular head movements.
- Pre-sitting infants showed less consistent ventral muscle activation, particularly during forward sway perturbations.
- The basic ventral muscle activation pattern in sitting infants showed similarities to adults, while dorsal muscle activation patterns differed.
Conclusions:
- Backward pelvic rotation is a key trigger for postural adjustments in independently sitting children.
- A foundational form of postural adjustment develops in a predetermined manner prior to independent sitting.
- Infant postural control exhibits a basic structure similar to adults, refined by sensory integration and central pattern generators.
Abstract:
This study examined whether postural responses emerge in children in a predetermined way before independent sitting is achieved, and in what respect postural responses in infants differ from those in adults. Children just able to sit independently and children not yet able to sit were exposed to surface perturbations (translation and rotation) while body movement and electromyographic (EMG) responses were recorded. Perturbations causing a backward sway of the body (i.e., forward translation and legs-up rotation), elicited consistent patterns of muscle activity in ventral hip, trunk, and neck muscles in the independently sitting children. A high tonic EMG background activity in trunk and neck extensor muscles was inhibited at the onset of the ventral muscle activity. Kinematic analysis revealed that backward rotation of the pelvis was the first detectable body movement, while head movements (linear and angular displacement) were irregular and occurred later than the pelvis movement. Perturbations in the opposite direction, causing a forward sway, evoked variable responses in dorsal trunk and neck muscles, suggesting that the excitability level for postural responses was set according to the stability limits of the body. Children not yet able to sit without support were tested when the support around the waist, given by the experimenter's hands, was released prior to the onset of the platform perturbation. Postural responses were elicited in ventral muscles following a backward sway in all children and in about 60% of all trials. Often, only some of the ventral muscles were activated. No distinct responses were evoked during perturbations imposing a forward sway. These results suggest that (1) backward rotation of the pelvis triggers the postural adjustments in the independently sitting children; (2) a basic form of the postural adjustment develops in a predetermined manner before children practice independent sitting; and (3) the basic structure of ventral muscle activation pattern resembles that of adults, while the activation of the dorsal muscles (inhibition) differs in several aspects. These findings are in agreement with a recent model of central pattern generators for postural responses consisting of two operative levels. At the first level, which is triggered by backward rotation of the pelvis, the basic activation pattern is generated. At the second level, the pattern is shaped and fine-tuned by multisensory interactions from all activated sensory systems.(ABSTRACT TRUNCATED AT 400 WORDS)