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Handedness, dexterity, and motor cortical representations
Jessica A Bernard1, Stephan F Taylor, Rachael D Seidler
1Department of Psychology, University of Michigan, Ann Arbor, Michigan, USA. jessbern@umich.edu
Journal of Neurophysiology
|October 15, 2010
Summary
The degree of hand preference, not just direction, influences motor system organization. Stronger hand preference correlates with faster interhemispheric interactions and more ipsilateral motor evoked potentials.
Area of Science:
- Neuroscience
- Motor Control
- Human Lateralization
Background:
- Motor system organization is known to vary with handedness.
- Previous research has primarily focused on the direction (right/left) of handedness, neglecting the degree or strength of handedness.
- Understanding the relationship between the degree of handedness and motor system characteristics is crucial for a comprehensive view of brain lateralization.
Purpose of the Study:
- To investigate the relationship between the degree of handedness and interhemispheric interactions.
- To determine if the degree of handedness correlates with contralateral and ipsilateral motor cortical representations.
- To explore the link between interhemispheric transfer time (IHTT) and motor cortical organization.
Main Methods:
- Participants underwent comprehensive handedness assessments, including preference and dexterity measures.
- Interhemispheric transfer time (IHTT) was estimated using a computerized Poffenberger paradigm.
- Transcranial magnetic stimulation (TMS) was used to map motor cortical representations bilaterally, recording muscle activity from the first dorsal interosseous muscle.
Main Results:
- A higher number of ipsilateral motor evoked potentials (iMEPs) were observed in individuals with less lateralized handedness.
- The number of iMEPs was correlated with interhemispheric transfer time (IHTT).
- While IHTT related to the symmetry of contralateral motor representations, handedness or dexterity lateralization did not show a direct relationship.
Conclusions:
- The degree of dexterity lateralization is associated with the likelihood of exhibiting iMEPs and the efficiency of interhemispheric communication.
- Interhemispheric transfer time (IHTT) is positively correlated with various measures of laterality and handedness.
- The precise neural pathways mediating iMEPs (direct ipsilateral projections vs. transcallosal transmission) require further investigation.
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