Journal of Neurophysiology, Vol 73, Issue 2 867-871, Copyright © 1995 by APS

ARTICLES

Operantly conditioned motoneuron plasticity: possible role of sodium channels

J. A. Halter, J. S. Carp and J. R. Wolpaw
Division of Restorative Neurology and Human Neurobiology, Baylor College of Medicine, Houston, Texas 77030, USA.

1. Learning is traditionally thought to depend on synaptic plasticity. However, recent work shows that operantly conditioned decrease in the primate H reflex is associated with an increase in the depolarization needed to fire the spinal motoneuron (VDEP) and a decrease in its conduction velocity (CV). Furthermore, the increase in VDEP appears to be largely responsible for the H-reflex decrease. The conjunction of these changes in VDEP and CV suggests that an alteration in Na+ channel properties throughout the soma and axon could be responsible. 2. A mathematical model of the mammalian myelinated axon was used to test whether a positive shift in the voltage dependence of Na+ channel activation, a decrease in Na+ channel peak permeability, or changes in other fiber properties could have accounted for the experimental findings. 3. A positive shift of 2.2 mV in Na+ channel activation reproduced the experimentally observed changes in VDEP and CV, whereas a reduction in Na+ channel permeability or changes in other fiber properties did not. 4. These results are consistent with the hypothesis that operantly conditioned decrease in the primate H reflex is largely due to a positive shift in the voltage dependence of Na+ channel activation. Recent studies suggest that change in activation of protein kinase C may mediate this effect.

This article has been cited by other articles:

				J. S. Carp, A. M. Tennissen, X. Y. Chen, and J. R. Wolpaw H-Reflex Operant Conditioning in Mice J Neurophysiol, October 1, 2006; 96(4): 1718 - 1727. [Abstract] [Full Text] [PDF]

				Y. Chen, X. Y. Chen, L. B. Jakeman, G. Schalk, B. T. Stokes, and J. R. Wolpaw The Interaction of a New Motor Skill and an Old One: H-Reflex Conditioning and Locomotion in Rats J. Neurosci., July 20, 2005; 25(29): 6898 - 6906. [Abstract] [Full Text] [PDF]

				K. Morgen, N. Kadom, L. Sawaki, A. Tessitore, J. Ohayon, H. McFarland, J. Frank, R. Martin, and L. G. Cohen Training-dependent plasticity in patients with multiple sclerosis Brain, November 1, 2004; 127(11): 2506 - 2517. [Abstract] [Full Text] [PDF]

				A. Karl, N. Birbaumer, W. Lutzenberger, L. G. Cohen, and H. Flor Reorganization of Motor and Somatosensory Cortex in Upper Extremity Amputees with Phantom Limb Pain J. Neurosci., May 15, 2001; 21(10): 3609 - 3618. [Abstract] [Full Text] [PDF]

				M. Hallett {blacksquare} REVIEW : Plasticity in the Human Motor System Neuroscientist, September 1, 1999; 5(5): 324 - 332. [Abstract] [PDF]

				X.-F. Zhang, X.-T. Hu, and F. J. White Whole-Cell Plasticity in Cocaine Withdrawal: Reduced Sodium Currents in Nucleus Accumbens Neurons J. Neurosci., January 1, 1998; 18(1): 488 - 498. [Abstract] [Full Text] [PDF]