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Published on: June 4, 2020
Development of finger force coordination in children
Sharon Shaklai1,2, Aviva Mimouni-Bloch2,3, Moran Levin4
1Department of Child and Youth Rehabilitation, Loewenstein Rehabilitation Hospital, Raanana, Israel.
Insights
Children aged 4-12 years improve finger force coordination by reducing errors, not increasing force. This skill, measured by the synergy index, develops linearly with age, enhancing dexterous tasks.
Area of Science:
- Developmental neuroscience
- Motor control
- Biomechanics
Background:
- Human motor control often involves complex coordination of multiple body parts.
- Optimal force production with multiple fingers requires a specific type of coordination where each finger compensates for others' errors, rather than producing similar forces.
- Understanding the developmental trajectory of this sophisticated motor skill in children is crucial for grasping typical motor development.
Purpose of the Study:
- To investigate the developmental changes in inter-finger force coordination in children aged 4-12 years.
- To determine if children develop the ability to use compensatory finger forces for improved motor task performance.
- To quantify this development using the uncontrolled manifold (UCM) hypothesis framework.
Main Methods:
- Recruited 60 typically developing children aged 4-12 years.
- Employed a finger-pressing task where participants controlled object height via total force output on sensors.
- Quantified inter-finger force coordination using the synergy index, derived from the uncontrolled manifold (UCM) hypothesis, analyzing "good" and "bad" variance in force production.
Main Results:
- A significant linear increase in the synergy index was observed as a function of age, indicating improved coordination.
- This improvement was primarily driven by a reduction in "bad" variance (errors) rather than an increase in "good" variance (task-relevant force).
- No significant gender differences were found, and the synergy index did not predict upper limb test outcomes beyond age.
Conclusions:
- Children aged 4-12 years demonstrate a developmental improvement in inter-finger force coordination, characterized by enhanced error compensation.
- This developing skill is linked to a reduction in motor noise and contributes to improved dexterous task performance.
- The findings highlight a specific aspect of motor skill acquisition in childhood, emphasizing coordination refinement over simple force enhancement.
Abstract:
Coordination is often observed as body parts moving together. However, when producing force with multiple fingers, the optimal coordination is not to produce similar forces with each finger, but rather for each finger to correct mistakes of other fingers. In this study, we aim to determine whether and how this skill develops in children aged 4-12 years. We measured this sort of coordination using the uncontrolled manifold hypothesis (UCM). We recorded finger forces produced by 60 typically developing children aged between 4 and 12 years in a finger-pressing task. The children controlled the height of an object on a screen by the total amount of force they produced on force sensors. We found that the synergy index, a measure of the relationship between "good" and "bad" variance, increased linearly as a function of age. This improvement was achieved by a selective reduction in "bad" variance rather than an increase in "good" variance. We did not observe differences between males and females, and the synergy index was not able to predict outcomes of upper limb behavioral tests after controlling for age. As children develop between the ages of 4 and 12 years, their ability to produce negative covariation between their finger forces improves, likely related to their improved ability to perform dexterous tasks.
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