Characterization of White Matter Tracts by Diffusion MR Tractography in Cat and Ferret that Have Similar Gyral Patterns.

The developmental relationships between gyral structures and white matter tracts have long been debated, but it is still difficult to discern whether they influence each other's development or are causally related. To explore this topic, this study used cats and ferrets as models for species that share similar gyral folding patterns and imaged with diffusion magnetic resonance imaging to compare white matter innervations in homologous gyri and other brain regions. Adult cat and ferret brains were analyzed via diffusion spectrum imaging tractography and homologous regions of interest were compared. Although similar genetic lineage and gyral structures would suggest analogous white matter tracts, tractography reveals significantly differing white matter connectivity in both the visual and auditory cortices. Similarities in connectivity were concentrated primarily in the highly conserved cerebellar region. These results correlate well with existing histological and functional studies of both species. Our results indicate that, while the 2 species may share similar gyral structures, they utilize different white matter connectivity; suggesting that while species may share similar gyral structures, they can develop different underlying white matter connectivity.