Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

Uneven densities of corticopontine neurons in the somatosensory cortex: a quantitative experimental study in the cat

  • 29 Accesses

  • 11 Citations


By use of large injections in the pontine nuclei of wheat germ agglutinin-horseradish peroxidase conjugate, the distribution of corticopontine cells in the primary somatosensory cortex (SI) was mapped quantitatively. The borders of the cytoarchitectonic areas 3a, 3b, 1 and 2, together constituting SI, were determined cyto- and myeloarchitectonically. Flat maps showing the distribution of labelled cells in SI were constructed. All labelled cells were confined to lamina V, and present in deep as well as superficial parts of this lamina. The size spectrum of the corticopontine cells seemed to encompass the whole range, from the smallest to the largest seen in lamina V of SI in thionin stained sections. Average densities of labelled corticopontine cells in SI varied from 114 to 248 per mm2 in different cases. No significant differences appear to exist between average densities in areas 3a, 3b, 1 and 2. However, densities vary consistently from medial to lateral within SI. When comparing this pattern with the physiological maps showing the somatotopical organization of SI, it appears that regions representing the trunk and proximal parts of the extremities have higher densities of corticopontine neurons than regions representing distal parts of the extremities and the face. The latter parts of SI have in common a much larger magnification factor than the former, that is, the volume of cortex devoted to a certain area in the periphery is much larger in e.g. the SI face region than in the trunk region. It thus would appear that the over-representation of the face and distal extremities in terms of cortical volume devoted ℴ them, is not upheld in terms of number of corticopontine neurons. Although apparently not paralleled in other connections of SI, the uneven densities of corticopontine projections from SI are very similar to what has been described previously in the corticopontine projections from visual areas 17, 18, and 19, where regions with the largest magnification factors have the lowest densities of corticopontine neurons. On the basis of these findings we suggest that sensory information from proximal body parts and peripheral parts of the visual field is relatively more important for the cerebellum, with its main function in movement control, than it is for parts of the brain engaged in more direct analysis of sensory messages.

This is a preview of subscription content, log in to check access.



Posterior sigmoid gyrus

Cru.s., Cr.s.:

Cruciate sulcus


Coronal sulcus


Anterior sigmoid gyrus


Coronal gyrus

Ans.s., An.s.:

Ansate sulcus


Lateral gyrus


Suprasylvian gyrus


Pontine nuclei


Nucleus reticularis tegmenti pontis


Medial lemniscus


Continuation in the pons of the cerebral peduncle


Brachium pontis


Trapezoid body


Superior olive


Medullary pyramid







Margin of coronal sulcus

Margin of cruciate sulcus

Margin of ansate sulcus


  1. Bjaalie JG (1985) Distribution in areas 18 and 19 of neurons projecting to the pontine nuclei: a quantitative study in the cat with retrograde transport of HRP-WGA. Exp Brain Res 57:585–597

  2. Bjaalie JG (1986) Distribution of corticopontine neurons in visual areas of the middle suprasylvian sulcus: quantitative studies in the cat. Neuroscience 18:1013–1033

  3. Bjaalie JG, Brodal P (1983) Distribution in area 17 of neurons projecting to the pontine nuclei: a quantitative study in the cat with retrograde transport of HRP-WGA. J Comp Neurol 221:289–303

  4. Brodal P (1968) The corticopontine projection in the cat. I. Demonstration of a somatotopically organized projection from the primary sensorimotor cortex. Exp Brain Res 5:210–234

  5. Brodal P (1978) The corticopontine projection in the rhesus monkey: origin and principles of organization. Brain 101:251–283

  6. Brodal P, Dietrichs E, Bjaalie JG, Nordby T, Walberg F (1983) Is lectin-coupled horseradish peroxidase taken up and transported by undamaged as well as by damaged fibers in the central nervous system? Brain Res 278:1–9

  7. Creutzfeldt OD (1983) Funktionelle Topographie sensorischer und motorischer Felder. In: Cortex cerebri: Leistung, strukturelle und funktionelle Organisation der Hirnrinde. Springer, Berlin, pp 161–165

  8. Daniel PM, Whitteridge D (1961) The representation of the visual field on the cerebral cortex in monkeys. J Physiol (Lond) 159:203–221

  9. Dhanarajan P, Rüegg DG, Wiesendanger M (1977) An anatomical investigation of the corticopontine projection in the primate (Saimiri sciureus): the projection from motor and somatosensory areas. Neuroscience 2:913–922

  10. Felleman DJ, Wall JT, Cusick CG, Kaas JH (1983) The representation of the body surface in S-I of cats. J Neurosci 3:1648–1669

  11. Glickstein M, May JG III, Mercier BE (1985) Corticopontine projection in the macaque: the distribution of labelled cortical cells after large injections of horseradish peroxidase in the pontine nuclei. J Comp Neurol 235:343–359

  12. Haartsen AB (1962) Cortical projections to mesencephalon, pons, medulla oblongata and spinal cord: an experimental study in the goat and rabbit. Eduard Ijdo, Leiden

  13. Hartmann-von Monakow K, Akert K, Künzle H (1981) Projection of precentral, premotor and prefrontal cortex to the basilar pontine grey and to nucleus reticularis tegmenti pontis in the monkey (Macaca fascicularis). Arch Suisses Neurol Neurochir Psychiat 129:189–208

  14. Hassler R, Muhs-Clement K (1964) Architectonischer Aufbau des sensomotorischen und parietalen Cortex der Katze. J Hirnforsch 6:377–420

  15. Jones EG, Wise SP (1977) Size, laminar and columnar distribution of efferent cells in the sensory-motor cortex of monkeys. J Comp Neurol 175:391–438

  16. Kaas JH (1983) What, if anything, is S-I? The organization of the “first somatosensory area” of cortex. Physiol Rev 63:206–231

  17. Kawamura K, Chiba M (1979) Cortical neurons projecting to the pontine nuclei in the cat: an experimental study with the horseradish peroxidase technique. Exp Brain Res 35:269–285

  18. McKenna TM, Whitsel BL, Dreyer DA, Metz CB (1981) Organization of cat anterior parietal cortex: relations among cytoarchitecture, single neuron functional properties, and interhemispheric connectivity. J Neurophysiol 45:667–697

  19. Mercier B, Legg C, Glickstein M (1988) Cells of origin of corticostriatal and corticopontine projections in the rat somatosensory cortex. Eur J Neurosci Suppl 1:245

  20. Mesulam M-M (1978) Tetramethyl benzidine for horseradish peroxidase neurochemistry: a non-carcinogenic blue reaction-product with superior sensitivity for visualizing neural afferents and efferents. J Histochem Cytochem 26:106–117

  21. Mihailoff GA, Burne RA, Woodward DJ (1978) Projections of sensorimotor cortex to the basilar pontine nuclei in the rat: an autoradiographic study. Brain Res 145:347–354

  22. Mihailoff GA, Lee H, Wattt CB, Yates R (1985) Projections to the basilar pontine nuclei from face sensory and motor regions of the cerebral cortex in the rat. J Comp Neurol 237:251–263

  23. Mountcastle VB (1957) Modality and topographic properties of single neurons of cat's somatic sensory cortex. J Neurophysiol 20:408–434

  24. Rosenquist AC (1985) Connections of visual cortical areas in the cat. In: Jones EG, Peters A (eds) Cerebral cortex, Vol 3. Plenum Press, New York London, pp 81–117

  25. Tomasch J (1968) The overall information capacity of the major afferent and efferent cerebellar cell and fiber systems. Confin Neurol 30:359–367

  26. Tomasch J (1989) The numerical capacity of the human corticoponto-cerebellar system. Brain Res 13:476–484

  27. Wiesendanger R, Wiesendanger M (1982a) The corticopontine system in the rat. I. Mapping of corticopontine neurons. J Comp Neurol 208:215–226

  28. Wiesendanger R, Wiesendanger M (1982b) The corticopontine system in the rat. II. The projection pattern. J Comp Neurol 208:227–238

  29. Wise SP, Jones EG (1977) Cells of origin and terminal distribution of descending projections of the rat somatic sensory cortex. J Comp Neurol 175:129–158

  30. Wong-Riley M (1979) Changes in the visual system of monocularly sutured or enucleated cats demonstrable with cytochrome oxidase histochemistry. Brain Res 53:11–28

Download references

Author information

Correspondence to P. Brodal.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Øverby, S.E., Bjaalie, J.G. & Brodal, P. Uneven densities of corticopontine neurons in the somatosensory cortex: a quantitative experimental study in the cat. Exp Brain Res 77, 653–665 (1989).

Download citation

Key words

  • Retrograde tracing
  • Somatosensory cortex
  • Somatotopy
  • Pontine nuclei
  • Cerebellum