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Hand digit control in children: motor overflow in multi-finger pressing force vector space during maximum voluntary

Jae Kun Shim1, Sohit Karol, Jeffrey Hsu

  • 1Department of Kinesiology, University of Maryland, 0110F HHP, College Park, MD 20742, USA. jkshim@umd.edu

Experimental Brain Research
|January 15, 2008
PubMed

Insights

Contralateral motor overflow in children shows task-dependent force magnitudes and directions. Motor overflow magnitude (MOM) and direction (MOD) varied by finger and movement type, with no age-related changes observed in this study.

Area of Science:

  • Neuroscience
  • Motor Control
  • Developmental Psychology

Background:

  • Contralateral motor overflow, the unintentional activation of muscles on the opposite side of the body during voluntary movement, is a common phenomenon.
  • Understanding motor overflow in children is crucial for insights into neural pathway development and motor skill acquisition.

Purpose of the Study:

  • To investigate contralateral motor overflow in children aged 5-11 years during single-finger and multi-finger maximum force production tasks.
  • To analyze the magnitude and direction of motor overflow in relation to finger-specific tasks and movement types (flexion/extension).

Main Methods:

  • Forty-five right-handed children produced maximum isometric pressing forces with single or four fingers of their right hand.
  • Forces from individual fingers of both hands were recorded and analyzed in a four-dimensional finger force vector space.
  • Motor overflow magnitude (MOM) and motor overflow direction (MOD) were calculated and compared across different tasks and age groups.

Main Results:

  • Increases in right-hand finger forces linearly correlated with left-hand finger forces, indicating contralateral motor overflow.
  • Motor overflow magnitude (MOM) was greater in extension than flexion, with the index finger flexion task showing the smallest MOM.
  • Motor overflow direction (MOD) was highest for index finger tasks and lowest for little finger tasks. A 'motor overflow surplus' was observed in four-finger tasks compared to single-finger tasks.
  • No significant age-related changes in MOM or MOD were found for single-finger or four-finger tasks.

Conclusions:

  • Contralateral motor overflow in children is influenced by the specific fingers involved and the magnitude/direction of the intended force.
  • The findings suggest a complex interplay of neural control mechanisms governing fine motor skills in developing children.
  • The lack of age-related changes in this cohort indicates that basic patterns of motor overflow are established early and are task-dependent.

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