Subcortical control of precision grip after human spinal cord injury

Bunday, K., Tazoe, T., Rothwell, J.C. and Perez, M.A. 2014. Subcortical control of precision grip after human spinal cord injury. Journal of Neuroscience. 21 (34), p. 7341–7350. doi:10.1523/JNEUROSCI.0390-14.2014

TitleSubcortical control of precision grip after human spinal cord injury
TypeJournal article
AuthorsBunday, K., Tazoe, T., Rothwell, J.C. and Perez, M.A.
Abstract

The motor cortex and the corticospinal system contribute to the control of a precision grip between the thumb and index finger. The involvement of subcortical pathways during human precision grip remains unclear. Using noninvasive cortical and cervicomedullary stimulation, we examined motor evoked potentials (MEPs) and the activity in intracortical and subcortical pathways targeting an intrinsic hand muscle when grasping a small (6 mm) cylinder between the thumb and index finger and during index finger abduction in uninjured humans and in patients with subcortical damage due to incomplete cervical spinal cord injury (SCI). We demonstrate that cortical and cervicomedullary MEP size was reduced during precision grip compared with index finger abduction in uninjured humans, but was unchanged in SCI patients. Regardless of whether cortical and cervicomedullary stimulation was used, suppression of the MEP was only evident 1-3 ms after its onset. Long-term (∼5 years) use of the GABAb receptor agonist baclofen by SCI patients reduced MEP size during precision grip to similar levels as uninjured humans. Index finger sensory function correlated with MEP size during precision grip in SCI patients. Intracortical inhibition decreased during precision grip and spinal motoneuron excitability remained unchanged in all groups. Our results demonstrate that the control of precision grip in humans involves premotoneuronal subcortical mechanisms, likely disynaptic or polysynaptic spinal pathways that are lacking after SCI and restored by long-term use of baclofen. We propose that spinal GABAb-ergic interneuronal circuits, which are sensitive to baclofen, are part of the subcortical premotoneuronal network shaping corticospinal output during human precision grip.

KeywordsBaclofen, corticospinal drive, primary motor cortex, spasticity, spinal motoneurons, voluntary drive
JournalJournal of Neuroscience
Journal citation21 (34), p. 7341–7350
ISSN0270-6474
Year2014
PublisherSociety for Neuroscience
Publisher's versionBunday et al., 2014_j neuro.pdf
Digital Object Identifier (DOI)doi:10.1523/JNEUROSCI.0390-14.2014
PubMed ID24849366
Web address (URL)http://www.jneurosci.org/content/34/21/7341.long
Publication dates
Published21 May 2014

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