| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Strength-duration characteristics for the stimulation of 131 raphespinal and reticulospinal axons in the spinal cord were determined using two types of stimulating electrode. Conduction velocity of these fibres ranged from 0.86 to 63 m/s. With silver wire (250 micron diameter) stimulating electrodes, chronaxies were: 0.18 +/- 0.06 ms for axons conducting between 16 and 63 m/s, 0.4 +/- 0.22 ms for axons conducting between 5 and 15 m/s and 2.06 +/- 0.79 ms for those with conduction velocity less than 5 m/s. There was an inverse relationship between chronaxie and conduction velocity. Rheobase values ranged from 7.4 to 400 microA but were independent of conduction velocity. Chronaxies obtained with wire electrodes were compared with those from stimulation of the same fibre through saline-filled micropipettes (2-12 micron tip diameter). Rheobase values with the micropipettes ranged from 1.6 to 20 microA, indicating a close proximity of the pipette to the axon. For these axons, chronaxies from metal wire electrodes ranged from 0.12 to 2.4 ms and for micropipettes from 0.04 to 0.65 ms. In almost all cases, chronaxies for micropipette stimulation were lower than those for metal wire electrodes. Furthermore, with micropipettes chronaxies were independent of conduction velocity. The results are shown to be related to differences in time constant of the activated region of axon and charge requirements of threshold activation. The two stimulating conditions, i.e. micro-electrodes compared with wire electrodes, are analogous to the theoretical point stimulated cable and uniformly polarized membrane cases. The results are discussed in relation to the possibility of determination of fibre type from stimulation characteristics. A distinction between chronaxies of myelinated and non-myelinated fibres can be made using wire electrodes of 250 micron diameter, but not with micro-stimulation, as with micropipettes (2-12 micron diameter).
This article has been cited by other articles:
|
|
 |
|
  E. J. Tehovnik, A. S. Tolias, F. Sultan, W. M. Slocum, and N. K. Logothetis Direct and Indirect Activation of Cortical Neurons by Electrical Microstimulation J Neurophysiol, August 1, 2006; 96(2): 512 - 521. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Shi and J. Whitebone Conduction Deficits and Membrane Disruption of Spinal Cord Axons as a Function of Magnitude and Rate of Strain J Neurophysiol, June 1, 2006; 95(6): 3384 - 3390. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Sinha, S. Karimi-Abdolrezaee, A. A. Velumian, and M. G. Fehlings Functional Changes in Genetically Dysmyelinated Spinal Cord Axons of Shiverer Mice: Role of Juxtaparanodal Kv1 Family K+ Channels J Neurophysiol, March 1, 2006; 95(3): 1683 - 1695. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. R. Bartlett, E. A. DeYoe, R. W. Doty, B. B. Lee, J. D. Lewine, N. Negrao, and W. H. Overman Jr Psychophysics of Electrical Stimulation of Striate Cortex in Macaques J Neurophysiol, November 1, 2005; 94(5): 3430 - 3442. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. J. Tehovnik, W. M. Slocum, C. E. Carvey, and P. H. Schiller Phosphene Induction and the Generation of Saccadic Eye Movements by Striate Cortex J Neurophysiol, January 1, 2005; 93(1): 1 - 19. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. M. Jensen and R. Shi Effects of 4-Aminopyridine on Stretched Mammalian Spinal Cord: The Role of Potassium Channels in Axonal Conduction J Neurophysiol, October 1, 2003; 90(4): 2334 - 2340. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Kohyama, Y.-Y. Lai, and J. M. Siegel Reticulospinal Systems Mediate Atonia With Short and Long Latencies J Neurophysiol, October 1, 1998; 80(4): 1839 - 1851. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
