Journal of Neuroscience, Vol 12, 3509-3524, Copyright © 1992 by Society for Neuroscience
Growth of the rat somatic sensory cortex and its constituent parts during postnatal development
D Riddle, A Richards, F Zsuppan and D Purves
Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710.
We have compared the size and arrangement of the primary somatic sensory
cortex (SI) and its constituent parts in juvenile (1 week old) and mature
(10-12 weeks old) rats using succinic dehydrogenase histochemistry and
digital image analysis. Our goal was to determine whether some regions of
the maturing cortex grow more than others. To this end, we examined (1) the
growth of barrels and the surrounding (interbarrel) cortex, (2) the growth
of the major somatic representations within SI, and (3) the overall growth
of SI compared to the neocortex as a whole. With respect to the first of
these issues, SI barrels and barrel-like structures grow more than the
intervening cortex. The growth of these elements varies according to
region: barrels in the head representation more than double in size,
whereas the barrel-like structures in the paw representations increase by
only about half this amount. The growth of the major somatic
representations within SI is also heterogeneous, the representation of the
head enlarging to a greater extent than the representations of the paws.
Thus, the ratio of the total area of head representation to the combined
paw representation is 15% greater in adults than in juveniles. Finally, the
primary somatic sensory cortex grows to a somewhat greater extent than the
neocortex as a whole. These observations demonstrate that postnatal
cortical growth is not uniform; it varies among cortical barrels and the
immediately surrounding (interbarrel) cortex, among the representations of
different body parts, and between SI and the rest of the neocortex. As an
explanation of this differential growth, we suggest that the neuropil of
metabolically (and/or electrically) more active cortical regions grows to a
greater extent during maturation than that of less active regions.
Previous Article | Next Article
