Plasticity of the corticospinal tract in early blindness revealed by quantitative analysis of fractional anisotropy based on diffusion tensor tractography.

Early visual deprivation may induce plastic changes, not only in the visual system, but also in the remaining sensory systems, secondary to altered experience in these spared modalities. Most of previous studies were focused on the plasticity of cortical areas of sensory modalities, but little attention was paid to the plasticity of motor system and white matter fiber tracts. Our purpose is to investigate the plasticity of the corticospinal tract (CST) in early blindness by tract-based quantitative analysis of fractional anisotropy (FA). Diffusion tensor imaging was performed in 17 early blind and 17 gender- and age-matched sighted subjects. The entire CST of each subject was reconstructed and the average FA of the tract was analyzed. To validate the results derived from the entire CST, we further analyzed a segment of the CST between the lowest slice of the cerebral peduncle and the uppermost slice of the lateral ventricle, in which the fibers are coherently arranged and the anatomical correspondence of the CST across subjects is established. On comparison with matched sighted participants, the average FA of the CST was significantly increased in the early blind men, but not in the early blind women. In conclusion, the plasticity of the CST is present in the early blind men, which might be related to the changes of motor experience during critical developmental period of the CST. This study also supports the perspective that experience-dependent plasticity occurs not only in the cortical areas but also in the white matter fiber tracts.