A comparative analysis of cellular morphological differentiation within the cerebral cortex using diffusion tensor imaging

Diffusion tensor imaging (DTI) is a magnetic resonance imaging (MRI) technique that provides information about cellular microstructure through measurements of water diffusion. Because inferences about neuroanatomy can be made from DTI, this methodology has been used to characterize cellular morphological changes associated with development of the cerebral cortex. Currently, however, the specific anatomical changes associated with DTI measurements directed at the cerebral cortex are incompletely characterized. Here, data collected in several laboratories, investigating five species (mouse, rat, ferret, baboon, and human), are compared to determine whether similarities in the trajectory of DTI measurements with development exist in the literature. Specifically, rates of change in fractional anisotropy (FA) of water diffusion were compared to rates of neuroanatomical development (based on the occurrence of specific neural events) in each species. In all species, decreases in FA with development were accurately approximated by fitting data to the same mathematical expression of exponential decay. Additionally, a high degree of correlation was found between rates of FA decay and rates of neuroanatomical development. This suggests that a common mechanism underlies decreases in FA with development across species. These results have two major implications. The ability of DTI to detect changes in neuroanatomy in the normal developing cerebral cortex introduces the potential for the use of this methodology in detecting cortical abnormalities associated with various developmental disorders. Additionally, the comparable patterns of neurodevelopment, and hence FA, across species imply that DTI methodology applied in non-human species can provide information about the human condition.