Brain tractography

The image shows a reconstruction of the physical connections between the different regions in an adult human brain. Via these connections, brain activity can travel from one part of the brain to another. The data for this image was obtained using diffusion-weighted magnetic resonance imaging - a non-invasive neuroimaging method that allows us to build detailed representations of brain connections in vivo. The geometry of these connections in the adult brain is of a daunting complexity. At the time of their formation, however, the brain is smaller and its shape simpler. To produce this image we deformed the brain in an attempt to recover this original simplicity. Using similar tools as those of ancient cartographers, we deformed the brain to combine multiple points of view into a single image showing the global structure of the brain's connections. The image shows a universal polar stereographic transformation of the 3D space embedding a dense human brain tractography. The tractography was computed from high-angular resolution diffusion weighted imaging data. The unfolding was performed from a ventral point of view showing the core white matter bundles: The cerebellum is located at the bottom of the image, callosal fibres are in the center, and the temporal lobes appear at the left and at the right of the representation. Diffusion weighted magnetic resonance imaging (DWI) is a neuroimaging technique where signal intensity at different brain regions is modulated by the local anisotropy of water diffusion. Using DWI data we can evaluate the existence of large white matter fibre bundles, estimate their local direction, and reconstruct their pathways. The resulting reconstruction of the macroscopic structure of brain connections is very complex. We developed a computer program which performs a universal polar stereographic transformation of the reconstructed streamlines. Our aim was to simplify their geometry to obtain a more intuitive representation of the global brain connectivity.