Combined DTI-fMRI Analysis for a Quantitative Assessment of Connections Between WM Bundles and Their Peripheral Cortical Fields in Verbal Fluency.

Diffusion tensor imaging (DTI) tractography and functional magnetic resonance imaging (fMRI) are powerful techniques to elucidate the anatomical and functional aspects of brain connectivity. However, integrating these approaches to describe the precise link between structure and function within specific brain circuits remains challenging. In this study, a novel DTI-fMRI integration method is proposed, to provide the topographical characterization and the volumetric assessment of the functional and anatomical connections within the language circuit. In a group of 21 healthy elderly subjects (mean age 68.5 ± 5.8 years), the volume of connection between the cortical activity elicited by a verbal fluency task and the cortico-cortical fiber tracts associated with this function are mapped and quantified. An application of the method to a case study in neuro-rehabilitation context is also presented. Integrating structural and functional data within the same framework, this approach provides an overall view of white and gray matter when studying specific brain circuits.

Comparison between skeleton-based and atlas-based approach in the assessment of corpus callosum damages in Mild Cognitive Impairment and Alzheimer Disease.

The damage of specific bundles in the brain white matter (WM) is currently assessed in Alzheimer Disease (AD) and amnestic Mild Cognitive Impairment (aMCI) by tractography based on diffusion tensor imaging (DTI) and the consequent evaluation of diffusion parameters in reconstructed tracts. Controversial results may be due to the use of different techniques. This work aims at comparing an atlas-based technique to compute fractional anisotropy (FA) in specific tracts with the voxelwise approach of Tract-Based Spatial Statistics (TBSS). FA was evaluated in 7 portions of the corpus callosum (CC) of 10 elderly healthy controls (HC), 10 aMCI and 10 mild AD patients with both approaches. Atlas-based tractography revealed concordant results with TBSS, displaying the same significant differences between AD and HC and no significant difference between aMCI and HC. However, as regards the AD to aMCI contrast only the atlas-based method was able to find significantly lowered FA in AD in frontal and parietal CC portions. This finding shows that a proper analysis which considers a higher number of voxels, not restricting the observation to the skeleton in the assessment of CC damages, could be useful for AD to aMCI differential diagnosis and prognosis.