Subcortical Contribution of Corticospinal Transmission during Visually Guided Switching Movements of the Arm
- 7 July 2021
- journal article
- research article
- Published by Oxford University Press (OUP) in Cerebral Cortex
- Vol. 32 (2), 380-396
- https://doi.org/10.1093/cercor/bhab214
Abstract
In animal experiments, the indirect corticospinal tract (CST) system via cervical interneurons has been shown to mediate motor commands for online adjustment of visuomotor behaviors, such as target-reaching. However, it is still unclear whether the similar CST system functions to perform similar motor behaviors in humans. To clarify this, we investigated changes in motor-evoked potentials (MEPs) in the elbow muscles following transcranial magnetic stimulation, transcranial electrical stimulation, or cervicomedullary stimulation while participants executed target-reaching and switching movements. We found that the MEP, whether elicited cortically or subcortically, was modulated depending on the direction of the switching movements. MEP facilitation began around the onset of the switching activities in an agonist muscle. Furthermore, ulnar nerve-induced MEP facilitation, which could be mediated by presumed cervical interneuronal systems, also increased at the onset of MEP facilitation. In a patient with cortical hemianopsia who showed switching movements in the scotoma, the MEPs were facilitated just before the switching activities. Our findings suggested that CST excitation was flexibly tuned with the switching movement initiation, which could partly take place in the subcortical networks, including the presumed cervical interneuronal systems.Funding Information
- Ministry of Education, Culture, Sports, Science and Technology (25 702 033, 26 560 282)
- Japan Society for the Promotion of Science (18 K10759, 23 500 617, 26 120 002)
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