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Brain Advance Access first published online on January 20, 2009
This version published online on January 26, 2009
Brain, doi:10.1093/brain/awn338
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© 2009 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

A subcortical oscillatory network contributes to recovery of hand dexterity after spinal cord injury

Yukio Nishimura1,2,*, Yosuke Morichika1 and Tadashi Isa1,2,3

1 Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki, Japan, 2 Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kawaguchi, Japan 3 Graduate University for Advanced Studies (SOKENDAI), Hayama, Japan

Correspondence to: Yukio Nishimura, Box 357330, University of Washington, Seattle, WA 981895, USA E-mail: yukio{at}u.washington.edu and Tadashi Isa, 38 Nishigonaka Myodaiji, Okazaki, Aichi 444-8585, Japan E-mail: tisa{at}nips.ac.jp

Recent studies have shown that after partial spinal-cord lesion at the mid-cervical segment, the remaining pathways compensate for restoring finger dexterity; however, how they control hand/arm muscles has remained unclear. To elucidate the changes in dynamic properties of neural circuits connecting the motor cortex and hand/arm muscles, we investigated the cortico- and inter-muscular couplings of activities throughout the recovery period after the spinal-cord lesion. Activities of antagonist muscle pairs showed co-activation and oscillated coherently at frequencies of 30–46 Hz ({gamma}-band) by 1-month post-lesion. Such {gamma}-band inter-muscular coupling was not observed pre-lesion, but emerged and was strengthened and distributed over a wide range of hand/arm muscles along with the recovery. Neither the β-band (14–30 Hz) cortico-muscular coupling observed pre-lesion nor a {gamma}-band oscillation was observed in the motor cortex post-lesion. We propose that a subcortical oscillator commonly recruits hand/arm muscles, via remaining pathways such as reticulospinal and/or propriospinal tracts, independent of cortical oscillation, and contributes to functional recovery.

Key Words: spinal cord injury; motor recovery; hand; rehabilitation; monkey

Abbreviations: ADP, adductor pollicis; BB, biceps brachii; CaMKII{alpha}, calmodulin-dependent protein kinase II{alpha}; CM, cortico-motoneuronal; CMC, cortico-muscular coupling; coM1, primary motor cortex in the contralesional hemisphere; CST, corticospinal tract; DR, deep radial; ECU, extensor carpi ulnaris; ED23, extensor digitorum 2 and 3; ED45, extensor digitorum 4 and 5; EDC, extensor digitorum communis; EMG, electromyography; FCR, flexor carpi radialis; FCU, flexor carpi ulnaris; FDI, first dorsal interosseus; FDS, flexor digitorum superficialis; IMC, inter-muscular coupling; l-CST, lateral corticospinal tract; ipM1, primary motor cortex in the ipsilesional hemisphere; LFPs, local field potentials; MI, motor cortex; PL, palmaris longus; PMv, ventral premotor cortex; SCL, spinal-cord lesion; Th12, 12th thoracic segment

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Received August 5, 2008. Revised October 14, 2008. Accepted November 14, 2008.

*Present address: Department of Physiology and Biophysics and Washington National Primate Research Center, University of Washington, Seattle, WA, USA


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