The Corpus Callosum as a Model System in the Study of Mammalian Cerebral Axons

A Comparison of Results from Primate and Rabbit
  • Harvey A. Swadlow


A large body of information is now available regarding the mechanism and the phenomonology of impulse conduction in invertebrate axons and in mammalian peripheral axons. Such axons, however, are of relatively large diameter when contrasted with their counterparts in the mammalian brain. Bishop (1966) has estimated that more than 80% of the fibers in the mammalian cortex are less than 3 μm in diameter, and in the pyramidal tract of the cat (Hildebrand and Skoglund, 1971) approximately 50% of the axons are less than 1 μm in diameter. The finest myelinated axons in the central nervous system are 0.2–0.3 μm in diameter (Bishop and Smith, 1964; Waxman and Bennett, 1972; Waxman and Swadlow, 1976a) while nonmyelinated axons may be as fine as 0.08 μm in diameter (Swadlow et al, 1980b; Waxman and Swadlow, 1976a).


Corpus Callosum Test Stimulus Conduction Velocity Myelinated Axon Axonal Branch 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Bishop, G. H., 1966, Fiber size and myelination in afferent systems, in:Pain( R. S. Knighton and P. R. Dunke, eds.), Churchill, London.Google Scholar
  2. Bishop, G. H., and Smith, J. M., 1964, The sizes of nerve fibers supplying the cerebral cortex, Exp. Neurol. 9:483–501.PubMedCrossRefGoogle Scholar
  3. Bishop, P. O., Burke, W., and Davis, R., 1962, Single-unit recording from antidromically activated optic radiation neurons, J. Physiol. (Lond.) 162:232–250.Google Scholar
  4. Bittner, G. D., 1968, Differentiation of nerve terminals in crayfish opener muscle and its functional significance, J. Gen. Physiol. 51:731–758.PubMedCrossRefGoogle Scholar
  5. Boyd, I. A., 1964, The relation between conduction velocity and diameter for the three groups of efferent fibres in nerves in mammalian skeletal muscle, J. Physiol. (Lond.) 175:33–35.Google Scholar
  6. Chiu, S. Y., and Ritchie, J. M., 1980, Potassium channels in nodal and internodal axonal membrane in mammalian myelinated fibers, Nature 284:170–171.PubMedCrossRefGoogle Scholar
  7. Chiu, S. Y., Ritchie, J. M., Robart, R. B., and Stagg, D., 1979, A quantitative description of membrane currents in rabbit myelinated nerve, J. Physiol. (Lond.) 292:149–166.Google Scholar
  8. Chung, S., Raymond, S. A., and Lettvin, J. Y., 1970, Multiple meaning in single visual units, Brain Behav. Evol. 3:73–101.Google Scholar
  9. Fleischhauer, K., and Wartenberg, H., 1967, Elektronenmikroskopische Untersuchungen uber das wachstum der nervenfasern und uber das auftreten von markscheiden im corpus callosum der katze, Z. Zellforsch. 83:568–581.CrossRefGoogle Scholar
  10. George, S. A., 1977, Changes in interspike interval during propagation:Quantitative description, Biol Cybern. 26:219–223.CrossRefGoogle Scholar
  11. Grossman, Y., Spira, M. E., and Parnas, I., 1973, Differential flow of information into branches of a single axon, Brain Res. 64:379–386.PubMedCrossRefGoogle Scholar
  12. Hildebrand, C., and Skoglund, S., 1971, Calibre spectra of some fibre tracts in the feline central nervous system during postnatal development, Acta Physiol Scand. Suppl. 364:5–42.PubMedGoogle Scholar
  13. Hodgkin, A. L., and Huxley, A. F., 1952, A quantitatve description of membrane current and its application to conduction and excitation in nerve, J. Physiol (Lond.) 117:500–544.Google Scholar
  14. Kaars, C., and Faber, D. S., 1981, Myelinated central vertebrate axon lacks voltage-sensitive potassium conductance, Science 212:1063–1065.PubMedCrossRefGoogle Scholar
  15. Kocsis, J. D., and Waxman, S. G., 1980, Absence of postassium conductance in central myelinated axons, Nature 287:348–349.PubMedCrossRefGoogle Scholar
  16. Kocsis, J. D., Swadlow, H. A., Waxman, S. G., and Brill, M. H., 1979, Variation in conduction velocity during the relative refractory and supernormal periods:A mechanism for impulse entrainment in central axons, Exp. Neurol 65:230–236.PubMedCrossRefGoogle Scholar
  17. Paintal, A. S., 1967, A comparison of the nerve impulses of mammalian nonmedullated nerve fibers with those of the smallest diameter medullated fibers, J. Physiol (Lond.) 193:523–533.Google Scholar
  18. Rockland, K. S., and Pandya, D. N., 1979, Laminar origins and terminations of cortical connections of the occipital lobe in the rhesus monkey, Brain Res. 179:3–20.PubMedCrossRefGoogle Scholar
  19. Rushton, W. A. H., 1951, A theory of the effects of fibre size in medullated nerve, J. Physiol (Lond.) 115:101–121.Google Scholar
  20. Seggie, J., and Berry, M., 1972, Ontogeny of interhemispheric evoked potentials in the rat:Significance of myelination of the corpus callosum, Exp. Neurol 35:215–232.PubMedCrossRefGoogle Scholar
  21. Shinoda, Y., Arnold, A. P., and Asanuma, H., 1976, Spinal branching of corticospinal axons in the cat, Exp. Brain Res. 26:215–234.PubMedCrossRefGoogle Scholar
  22. Swadlow, H. A., 1974, Systematic variations in the conduction velocity of slowly conducting axons in the rabbit corpus callosum, Exp. Neurol 43:445–451.PubMedCrossRefGoogle Scholar
  23. Swadlow, H. A., 1982a, Antidromic activation:Measuring the refractory period at the site of axonal stimulation, Exp. Neurol 75:514–519.CrossRefGoogle Scholar
  24. Swadlow, H. A., 1982b, Impulse conduction in the mammalian brain:Physiological properties of individual axons monitored for several months, Science 218:911–913.CrossRefGoogle Scholar
  25. Swadlow, H. A., and Waxman, S. G., 1975, Observations on impulse conduction along central axons, Proc. Natl Acad. Sci. USA 72:5156–5159.PubMedCrossRefGoogle Scholar
  26. Swadlow, H. A., and Waxman, S. G., 1976, Variations in conduction velocity and excitability following single and multiple impulses of visual callosal axons in the rabbit, Exp. Neurol 53:128–150.PubMedCrossRefGoogle Scholar
  27. Swadlow, H. A., and Weyand, T. G., 1981, Efferent systems of the rabbit visual cortex:Laminar distribution of the cells of origin, axonal conduction velocities, and identification of axonal branches, J. Comp. Neurol 203:799–822.PubMedCrossRefGoogle Scholar
  28. Swadlow, H. A., Rosene, D. L., and Waxman, S. G., 1978a, Characteristics of interhemispheric impulse conduction between prelunate gyri of the rhesus monkey, Exp. Brain Res. 33:455–467.CrossRefGoogle Scholar
  29. Swadlow, H. A., Waxman, S. G., and Rosene, D. L., 1978b, Latency variability and the identification of antidromically activated units in mammalian brain, Exp. Brain Res. 32:439–143.CrossRefGoogle Scholar
  30. Swadlow, H. A., Weyand, T. G., and Waxman, S. G., 1978c, The cells of origin of the corpus callosum in rabbit visual cortex, Brain Res. 156:129–134.CrossRefGoogle Scholar
  31. Swadlow, H. A., Geschwind, N., and Waxman, S. G., 1979, Commissural transmission in humans (technical comment), Science 204:530–531.PubMedCrossRefGoogle Scholar
  32. Swadlow, H. A., Kocsis, J. D., and Waxman, S. G., 1980a, Modulation of impulse conduction along the axonal tree, Annu. Rev. Biophys. Bioeng. 9:143–179.CrossRefGoogle Scholar
  33. Swadlow, H. A., Waxman, S. G., and Geschwind, N., 1980b, Small-diameter non-myelinated axons in the primate corpus callosum, Arch. Neurol. 37:114–115.Google Scholar
  34. Swadlow, H. A., Waxman, S. G., and Weyand, T. G., 1981, Effects of variations in temperature on impulse conduction along nonmyelinated axons in the mammalian brain, Exp. Neurol. 71:383–389.PubMedCrossRefGoogle Scholar
  35. Tasaki, I., 1959, Conduction of the nerve impulse, in:Handbook of Physiology(J. Field and H. W. Magoun, eds.), American Physiological Society, Washington, D. C., Vol. I, pp. 75–122.Google Scholar
  36. Tomasch, J., 1954, Size, distribution, and number of fibers in the human corpus callosum, Anat. Rec. 119:119–135.PubMedCrossRefGoogle Scholar
  37. Tomasch, J., and MacMillan, A., 1957, The number of fibers in the corpus callosum of the white mouse, J Comp. Neurol. 100:165–168.CrossRefGoogle Scholar
  38. Waxman, S. G., 1972, Regional differentiation of the axon:A review with special reference to the concept of the multiplex neuron, Brain Res. 47:269–288.PubMedCrossRefGoogle Scholar
  39. Waxman, S. G., and Bennett, M. V. L., 1972, Relative conduction velocities of small myelinated and non-myelinated fibres in the central nervous system, Nature New Biol. 238:217–218.PubMedCrossRefGoogle Scholar
  40. Waxman, S. G., and Swadlow, H. A., 1976a, Ultrastructure of visual callosal axons in the rabbit, Exp. Neurol. 53:115–128.CrossRefGoogle Scholar
  41. Waxman, S. G., and Swadlow, H. A., 1976b, Morphology and physiology of visual callosal axons:Evidence for a supernormal period in central myelinated axons, Brain Res. 113:179–187.CrossRefGoogle Scholar

Copyright information

© Plenum Press, New York 1985

Authors and Affiliations

  • Harvey A. Swadlow
    • 1
  1. 1.Department of PsychologyUniversity of ConnecticutStorrsUSA

Personalised recommendations