Imaging white-matter pathways of the auditory system with diffusion imaging tractography

The recent advent of diffusion imaging tractography has opened a new window into the in vivo white-matter anatomy of the human brain. This is of particular importance for the connections of the auditory system, which may have undergone substantial development in humans in relation to language. However, tractography of the human auditory pathways has proved to be challenging due to current methodologic limitations and the intrinsic anatomic features of the subcortical connections that carry acoustic information in the brainstem. More reliable findings are forthcoming from tractography studies of corticocortical connections associated with language processing. In this chapter we introduce the reader to basic principles of diffusion imaging and tractography. A selected review of the tractography studies of the auditory pathways will be presented, with particular attention given to the cerebral association pathways of the temporal lobe. Finally, new diffusion methods based on advanced model for mapping fiber crossing will be discussed in the context of the auditory and language networks.