ReviewUnraveling the secrets of white matter - Bridging the gap between cellular, animal and human imaging studies

- White matter macrostructural measurements explained.
- Introduction to how MRI imaging can be used to understand changes within the white matter.
- Estimation of the white matter microstructures, cells and axons, occupying an imaging voxel.
- Biological methods used for white matter studies explained.

The CNS white matter makes up about half of the human brain, and with advances in human imaging it is increasingly becoming clear that changes in the white matter play a major role in shaping human behavior and learning. However, the mechanisms underlying these white matter changes remain poorly understood. Within this special issue of Neuroscience on white matter, recent advances in our knowledge of the function of white matter, from the molecular level to human imaging, are reviewed. Collaboration between fields is essential to understand the function of the white matter, but due to differences in methods and field-specific 'language', communication is often hindered. In this review, we try to address this hindrance by introducing the methods and providing a basic background to myelin biology and human imaging as a prelude to the other reviews within this special issue.