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Synaptic linkages between corticomotoneuronal cells affecting forelimb muscles in behaving primates
1Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195-7290, USA.
Journal of Neurophysiology
|June 12, 2009
Summary
This study reveals how motor cortex cells connect to control primate forelimb muscles. Common synaptic input influences corticomotoneuronal cells with overlapping muscle targets, forming distributed cortical colonies.
Area of Science:
- Neuroscience
- Motor Control
- Primate Physiology
Background:
- Understanding the neural circuits controlling voluntary movement is crucial.
- The motor cortex plays a key role in modulating muscle activity.
- The specific synaptic interactions among motor cortex cells remain incompletely understood.
Purpose of the Study:
- To investigate synaptic interactions between neighboring motor cortex cells.
- To identify how these interactions influence primate forelimb muscle control.
- To determine the role of synchronized firing in corticomotoneuronal (CM) cell output.
Main Methods:
- Simultaneous extracellular recording of cortical cell pairs in monkeys performing wrist torque tasks.
- Identification of CM cells via postspike effects on electromyographs (EMGs) using spike-triggered averages (SpTAs).
- Analysis of synaptic interactions using cross-correlograms of action potentials.
Main Results:
- Synchrony peaks in cross-correlograms between CM and non-CM cells did not mediate postspike effects.
- Half of simultaneously recorded CM cell pairs showed synchrony peaks, often correlating with shared target muscles.
- CM cell pairs affecting different muscles, including synergistic ones, typically lacked synchrony peaks.
Conclusions:
- Common synaptic input specifically targets CM cells with overlapping muscle fields.
- Cortical control of forelimb muscles involves a wide and overlapping distribution of "cortical colonies."
- These findings provide insights into the organization of motor cortical circuitry for complex movements.
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