Long-Term Monitoring of Post-Stroke Plasticity After Transient Cerebral Ischemia in Mice Using In Vivo and Ex Vivo Diffusion Tensor MRI

We used a murine model of transient focal cerebral ischemia to study: 1) in vivo DTI long-term temporal evolution of the apparent diffusion coefficient (ADC) and diffusion fractional anisotropy (FA) at days 4, 10, 15 and 21 after stroke 2) ex vivo distribution of a plasticity-related protein (GAP-43) and its relationship with the ex vivo DTI characteristics of the striato-thalamic pathway (21 days)

Validation of tractography against in vivo tracing in the macaque visual system: effect of distance correction

Validation of diffusion imaging has proved difficult due to the lack of an adequate gold-standard. In this work, the macaque visual system is used as a model, in which due to an extensive literature of in-vivo and post-mortem tracer studies, true connections are well-established. We performed probabilistic tractography on diffusion imaging data from two in-vitro macaque brains, and comparisons were made between identified connections at different thresholds of connection strength, and connections identified in the visual system wiring map of Felleman & van Essen. The effects of streamline-length based correction of the distance bias of probabilistic tractography were also explored

Diffusion Tensor Imaging–Based Characterization of Brain Neurodevelopment in Primates

Primate neuroimaging provides a critical opportunity for understanding neurodevelopment. Yet the lack of a normative description has limited the direct comparison with changes in humans. This paper presents for the first time a cross-sectional diffusion tensor imaging (DTI) study characterizing primate brain neurodevelopment between 1 and 6 years of age on 25 healthy undisturbed rhesus monkeys (14 male, 11 female). A comprehensive analysis including region-of-interest, voxel-wise, and fiber tract–based approach demonstrated significant changes of DTI properties over time. Changes in fractional anisotropy (FA), mean diffusivity, axial diffusivity (AD), and radial diffusivity (RD) exhibited a heterogeneous pattern across different regions as well as along fiber tracts. Most of these patterns are similar to those from human studies yet a few followed unique patterns. Overall, we observed substantial increase in FA and AD and a decrease in RD for white matter (WM) along with similar yet smaller changes in gray matter (GM). We further observed an overall posterior-to-anterior trend in DTI property changes over time and strong correlations between WM and GM development. These DTI trends provide crucial insights into underlying age-related biological maturation, including myelination, axonal density changes, fiber tract reorganization, and synaptic pruning processes