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Ipsilateral corticospinal projections do not predict congenital mirror movements: a case report
T Verstynen1, R Spencer, C M Stinear
1Department of Psychology, University of California, Berkeley, CA 94720, USA. timothyv@gmail.com
Neuropsychologia
|October 7, 2006
Summary
Congenital mirror movements (CMMs) involve involuntary hand movements. This study found CMMs stem from bilateral motor cortex activation during movement execution, not planning.
Area of Science:
- Neuroscience
- Motor Control
- Human Physiology
Background:
- Congenital mirror movements (CMMs) are involuntary, symmetric movements of one hand accompanying voluntary movements of the other.
- Previous hypotheses suggested CMMs result from excessive ipsilateral motor cortex projections.
Observation:
- This study investigated CMMs in an individual with pronounced symptoms.
- Transcranial magnetic stimulation (TMS) mapped motor cortex input to hand muscles during voluntary contraction.
- Mirror movements were strongest in muscles with dominant contralateral representation.
Findings:
- Contrary to expectations, CMMs were not linked to muscles activated by stimulation from either hemisphere.
- Results support a bilateral motor cortex control hypothesis for CMMs.
- fMRI confirmed bilateral motor cortex activity during intended unimanual movements.
Implications:
- Bilateral motor cortex recruitment during unilateral actions in CMMs occurs during movement execution, not motor planning.
- This challenges previous models and suggests a different neural mechanism for CMMs.
- Understanding CMMs offers insights into motor control and hemispheric interactions.
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