Vibrissaeless mutant rats with a modular representation of innervated sinus hair follicles in the cerebral cortex.

Specialized areas in the cerebral cortex are essential to mediate the various sensory modalities and are crucial to their recovery in disease. We recently observed that prenatal photoreceptor cues are not indispensable for the development of the elaborate modular organization of the primate primary visual (striate) cortex (Kuljis, R. O. and P. Rakic. 1990. Proc. Natl. Acad. Sci. USA 87: 5303-5306). By contrast, the elegant experiments of Woolsey, Van der Loos, and collaborators (Van der Loos, H., and T. A. Woolsey. 1973. Science 179: 395-398; Van der Loos, H. and J. Dörfl. 1978. Neurosci Lett. 7: 23-30; Woolsey, T. A. 1967. John Hopkins Med. J. 121: 91-112; Woolsey, T. A. and H. Van der Loos. 1970. Brain Res. 17: 205-242) indicate that postnatal vibrissal receptor input is necessary for the development of modular organization in the posteromedial barrel subfield (PMBSF) of the rodent somatosensory cortex. The present report is part of a series of studies designed to address the variables that result in seemingly different results in these two models. Here, I address the role of pre- and postnatal tactile experience in the development of the rat homologue of the mouse PMBSF using mutants that lack vibrissae. Mutants exhibit cytoarchitectonic units in layer IV similar to those in controls, as revealed by NissI stains and histochemistry for succinate dehydrogenase and cytochrome oxidase. Sections from flat mounts of the vibrissal pad reveal that all mutants contain vibrissal follicles with stumps of sinus hairs in a geometric array and number similar to that in controls, and that the follicles are innervated heavily by fascicles of fibers from the infraorbital nerve.(ABSTRACT TRUNCATED AT 250 WORDS)