RESEARCH ARTICLE In Vivo Tractography of Fetal Association Fibers

Association fibers connect different cortical areas within the same hemisphere and consti-tute an essential anatomical substrate for a diverse range of higher cognitive functions. So far a comprehensive description of the prenatal in vivo morphology of these functionally im-portant pathways is lacking. In the present study, diffusion tensor imaging (DTI) and tracto-graphy were used to visualize major association fiber tracts and the fornix in utero in preselected non-motion degraded DTI datasets of 24 living unsedated fetuses between 20 and 34 gestational weeks (GW). The uncinate fasciculus and inferior fronto-occipital fascic-ulus were depicted as early as 20 GW, while in vivo 3D visualization of the inferior longitudi-nal fasciculus, cingulum and fornix was successful in older fetuses during the third trimester. Provided optimal scanning conditions, in utero DTI and tractography have the po-tential to provide a more accurate anatomical definition of developing neuronal networks in the human fetal brain. Knowledge about the normal prenatal 3D association tract morpholo-gy may serve as reference for their assessment in common developmental diseases