How the ventral pathway got lost: and what its recovery might mean.

Textbooks dealing with the anatomical representation of language in the human brain display two language-related zones, Broca's area and Wernicke's area, connected by a single dorsal fiber tract, the arcuate fascicle. This classical model is incomplete. Modern imaging techniques have identified a second long association tract between the temporal and prefrontal language zones, taking a ventral course along the extreme capsule. This newly identified ventral tract connects brain regions needed for language comprehension, while the well-known arcuate fascicle is used for "sensorimotor mapping" during speech production. More than 130 years ago, Carl Wernicke already described a ventral connection for language, almost identical to the present results, but during scientific debate in the following decades either its function or its existence were rejected. This article tells the story of how this knowledge was lost and how the ventral connection, and in consequence the dual system, fits into current hypotheses and how language relates to other systems.