For many years the study of the brain has been based primarily on the grey matter despite the fact that it is known that damage to the white matter of the brain can also produce significant deficits.

More recently it has been shown that the microstructural characteristics of the white matter in healthy individuals also correlate with their cognitive abilities and that the integrity of the white matter correlates with functional measures of brain activity or neuromodulation effects.

Understanding the role of white matter connections in the healthy and damaged brain therefore seems essential in the study of human cognition.