Very intersting find. Though every time I see 'simple 3D grid' in combination with the brain, I think 'scanner or reconstruction artifact'. For my PhD research I've worked with DTI (Diffusion Tensor Imaging) data which was very hard to sensibly interpret as 'connectivity': The visualized structures depended very much on the parameters and reconstruction method used. And it was hard to match the visualized structures to actual physical structures.
I wonder if they verified in some other way (ie, microscope) that the simple 3D structures were really there. If so, very exciting news!