The Journal of comparative neurology
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Normally, axons within the corpus callosum are ordered according to the cortical regions from which they originate, and callosal cells and terminations form elaborate cortical patterns related to the underlying topographic representations of the sensory periphery. About 30% of mice of the BALB/c strain show congenital deficiencies of the callosal commissure which range from total absence of the corpus callosum to a moderate reduction in the size of this commissure. In the light of current theories about the origin of these callosal deficiencies, it seems likely that fibers crossing the midplane in mutant mice have to circumvent local disturbances along their migration path. ⋯ Within the context of current theories about the origin of congenital callosal deficiencies, our findings suggest that callosal fibers are able to establish appropriate contralateral connections in spite of alterations of their migration route. They also suggest that fiber topography within the corpus callosum does not play an important role in guiding migrating axons to their correct contralateral targets. Finally, our failure to find labeled fibers within the anterior commissure indicates that this commissure does not serve as an alternative route for deviated callosal axons.