Undoubtedly, studying the units—be it neurons or brain areas—in isolation is indispensible for explaining brain processes in health and disease.
The buzz-word is connectome: the matrix of structural links and functional associations between the basic units of the central nervous system.
The technique, introduced in the 1980’s, is called diffusion weighted imaging (DWI; or diffusion MRI).
The name is conveniently derived from its working principle.
The brain cells’ microstructural constituents hinder diffusion of water molecules in the brain.