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Motor command for precision grip in the macaque monkey can be mediated by spinal interneurons
B Alstermark1, L G Pettersson, Y Nishimura
1Department of Integrative Medical Biology, Section of Physiology, Umeå University, Umeå, Sweden. Bror.Alstermark@physiol.umu.se
Journal of Neurophysiology
|April 23, 2011
Summary
Spinal interneurons can mediate precise finger movements. C3-C4 propriospinal interneurons transmit commands for precision grip, challenging the view that only direct pathways control such actions.
Area of Science:
- Neuroscience
- Motor Control Research
- Spinal Cord Physiology
Background:
- Spinal interneurons are traditionally linked to reflexes and automatic movements.
- The role of spinal interneurons in voluntary, independent finger movements remains debated.
- The direct corticomotoneuronal pathway's exclusive role in fine motor control is questioned.
Purpose of the Study:
- To investigate if spinal interneurons can mediate cortical commands for independent finger movements.
- To determine the contribution of C3-C4 propriospinal interneurons to precision grip.
- To differentiate the roles of the corticospinal tract and propriospinal pathways in fine motor control.
Main Methods:
- Training macaque monkeys in a precision grip task (picking up food).
- Performing lateral corticospinal tract (CST) lesions at different spinal levels (C4/C5 and C2).
- Assessing the monkeys' ability to perform precision grip after CST lesions.
Main Results:
- Monkeys could perform precision grip after CST lesions at C4/C5.
- Precision grip was not possible after CST lesions at C2.
- C3-C4 propriospinal interneurons were identified as projecting to hand and arm motoneurons.
Conclusions:
- C3-C4 propriospinal interneurons are capable of transmitting the cortical command for precision grip.
- This finding challenges the notion that only direct corticomotoneuronal pathways control independent finger movements.
- Spinal interneurons play a significant role in voluntary fine motor control.
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