Summary
The development of neurons and their synapses of the mouse motor cortex has been studied from the first postnatal day up to an age of three weeks both electronmicroscopically and with the Golgi method. Special attention has been paid to the maturation of the different cell types in the sixth cortical layer and their dendritic organization within this layer.
The polymorph layer is subdivided into two zones: an internal (VIb) and an external one (VIa). In these zones six different cell types can be identified both electronmicroscopically and with the Golgi method: large, small and inverted pyramidal cells in VIa; horizontal cells, star cells and small pyramidal cells in VIb.
Spines of apical dendrites of large pyramidal cells in sublayer VIa can be detected as early as the 6th postnatal day. About the ninth day the basal dendrites as well show emerging spines. Somatic spines are found only on the large pyramidal cells and disappear slowly towards the end of the 3rd postnatal week.
The small pyramidal cells show developing spines on their apical dendrite in the first half of the second postnatal week. The final density and distribution of spines is reached by the stem dendrites towards the end of the second week, by the basal dendrites during the third week. The maturation process of the “improperly orientated” neurons occurs in time in between the large and the small pyramidal cells.
The axo-somatic synapses appear in general at a later date than the axo-dendritic ones. In the horizontal cells axo-somatic synapses are visible already at the seventh postnatal day.
At the end of the first week especially in layer VIb many immature neurons with an ovoid or round nucleus are present having little if any endoplasmic reticulum organised as ergastoplasm.
Towards the end of the second week however most neurons in the polymorph layer have a well developed endoplasmic reticulum.
Electronmicroscopical pictures reveal in outgrowing dendrites many enlargements filled with vesicles, these correspond to the varicosities seen in Golgi pictures. At nine days postnatally the first myelinated fibres appear.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Angevine, J. B., and R. L. Sidman: Autoradiographic study of cell migration during histogenesis of cerebral cortex in the mouse. Nature (Lond.) 192, 766–768 (1961).
Berry, M., and J. T. Eayrs: Histogenesis of the cerebral cortex. Nature (Lond.) 197, 984–985 (1963).
—, A. W. Rogers, and J. T. Eayrs: Pattern of cell migration during cortical histogenesis. Nature (Lond.) 203, 591–593 (1964).
Bunge, M. B., R. P. Bunge, and E. R. Peterson: The onset of synapse formation in spinal cord cultures as studied by electron microscopy. Brain Res. 6, 728–749 (1967).
Colonnier, M.: The tangential organization of the visual cortex. J. Anat. (Lond.) 98, 327–344 (1964).
—: The fine structural arrangement of the cortex. Arch. Neurol. (Chic.) 16, 651–657 (1967).
Dalton, A. J.: A chrome-osmium fixative for electron microscopy. Anat. Rec. 121, 281 (1955).
Gray, E. G.: Axo-somatic and axo-dendritic synapses of the cerebral cortex: an electron microscope study. J. Anat. (Lond.) 93, 420–433 (1959).
Hubel, D. H., and T. N. Wiesel: Receptive fields, binocular interaction and functional architecture in the cat's visual cortex. J. Physiol. (Lond.) 160, 106–154 (1962).
Isenschmid, R.: Zur Kenntnis der Großhirnrinde der Maus. Abh. Kgl. Preuß. Akad. Wiss. Berlin, phys.-math. Kl., Abh. 3, 1–46 (1911).
Loos, H. van der: The “improperly” orientated pyramidal cell in the cerebral cortex and its possible bearing on problems of neuronal growth and cell orientation. Bull. Johns Hopk. Hosp. 117, 228–250 (1965).
Lorente de Nó, R.: La corteza cerebral del ratón. Lab. Invest. biol. Univ. Madrid 20, 41–78 (1922).
Meller, K., W. Breipohl, and P. Glees: Early cytological differentiations in the cerebral hemisphere of mice. An electronmicroscopical study. Z. Zellforsch. 72, 525–533 (1966).
—: The cytology of the developing molecular layer of mouse motor cortex. An electron microscopical and a Golgi impregnation study. Z. Zellforsch. 86, 171–183 (1968a).
—: Synaptic organization of the molecular and the outer granular layer in the motor cortex in the white mouse during postnatal development. A Golgi and electronmicroscopical study. Z. Zellforsch. 92, 217–231 (1968b).
Mountcastle, V. B.: Modalities and topographic properties of single neurons of cat's sensory cortex. J. Neurophysiol. 20, 408–434 (1957).
Noback, C., and D. P. Purpura: Postnatal ontogenesis of neurons in cat neocortex. J. comp. Neurol. 117, 291–307 (1961).
Pappas, G. D., and D. P. Purpura: Fine structure of dendrites in the superficial neocortical neuropil. Exp. Neurol. 4, 507–530 (1961).
—: Electron microscopy of immature human and feline neocortex. In: Progress in brain res., vol. 4, p. 176–186, ed. by D. P. Purpura and J. P. Schadé. Amsterdam-London-New York: Elsevier 1964.
Purpura, D. P., M. W. Carmichael, and E. M. Housepian: Physiological and anatomical studies of development of superficial axo-dendritic synaptic pathways in neocortex. Exp. Neurol. 2, 324–347 (1960).
Ramón y Cajal, S.: Studien über die Hirnrinde des Menschen, H. 2. Die Bewegungsrinde. Leipzig: Johann Ambrosius Barth 1900.
—: Studien über die Hirnrinde des Menschen, H. 5. Vergleichende Strukturbeschreibung und Histogenesis der Hirnrinde. Leipzig: Johann Ambrosius Barth 1906.
—, and F. de Castro: Técnica micrográfica del sistema nervioso. Madrid: Tipografía artística 1933.
Scholl, D. A.: The organization of the cerebral cortex. London: Methuen & Co. Ltd. 1956.
Voeller, K., G. D. Pappas, and D. P. Purpura: Electron microscope study of development of cat superficial neocortex. Exp. Neurol. 7, 107–130 (1963).
Author information
Authors and Affiliations
Additional information
Aided by grant (R-209-67) from the United Cerebral Palsy Research and Educational Foundation, New York.
Rights and permissions
About this article
Cite this article
Meller, K., Breipohl, W. & Glees, P. Ontogeny of the mouse motor cortex. The polymorph layer or layer VI. A Golgi and electronmicroscopical study. Z. Zellforsch. 99, 443–458 (1969). https://doi.org/10.1007/BF00337614
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00337614