Related Experiment Videos
Cortical outflow to proximal arm muscles in man
J G Colebatch1, J C Rothwell, B L Day
1MRC Human Movement and Balance Unit, National Hospital for Nervous Diseases, London, UK.
Brain : a Journal of Neurology
|December 1, 1990
Summary
This study reveals direct corticospinal projections to shoulder muscles in humans, with stronger influence on the deltoid than the pectoralis major. These findings may explain muscle strength patterns after stroke.
Area of Science:
- Neuroscience
- Motor Control
- Human Physiology
Background:
- The corticospinal tract is crucial for voluntary movement.
- Its projections to proximal limb muscles in humans are less understood than to distal muscles.
Purpose of the Study:
- To investigate direct corticospinal influences on antagonistic shoulder muscles (deltoid and pectoralis major) in humans.
- To characterize the latency and strength of these projections using non-invasive cortical stimulation.
Main Methods:
- Recorded single motor unit discharges from deltoid and pectoralis major muscles in 6 volunteers.
- Used anodal electrical and magnetic cortical stimulation to evoke responses.
- Constructed post-stimulus time histograms to analyze motor unit excitation.
Main Results:
- Anodal stimulation evoked short-latency excitation in both muscles, suggesting direct corticospinal input.
- Estimated excitatory postsynaptic potential (EPSP) amplitudes were 5.5 mV for deltoid and 2.2 mV for pectoralis major.
- Magnetic stimulation revealed medium-latency excitation, potentially from bilateral pathways, independent of current direction.
Conclusions:
- Direct corticomotoneuronal projections exist to proximal muscles of the contralateral arm in humans.
- The deltoid receives a stronger projection than its antagonist, the pectoralis major.
- A potential bilateral pathway to proximal muscles may explain differential recovery of arm strength after stroke.