The organizational variability of the rodent somatosensory cortex.

Rodentia is the largest mammalian order, with more than 2,000 species displaying a great diversity of morphological characteristics and living in different ecological niches (terrestrial, semi-aquatic, arboreal and fossorial). Analysis of the organization of the somatosensory areas in six species of rodents allowed us to demonstrate that although these species share a similar neocortical blueprint with other eutherian mammals, important differences exist between homologous areas across different species, probably as a function of both lifestyle and peripheral sensory specializations typical of each species. We based this generalization on a phylogenetic comparison of the intrinsic organization of the primary somatosensory area (SI) across representatives of different rodent suborders. This analysis revealed considerable structural variability, including the differential expansion of cortical representation of specific body parts (cortical amplification) as well as the parcellation of areas into processing modules.