But there have always been naysayers who pointed to evidence that failed to fit this tidy picture. Now a study employing a powerful variant of magnetic resonance imaging (MRI) confirms these suspicions. The study will be published December 13, 2004 in the online edition of Annals of Neurology (http://www.interscience.wiley.com/journal/ana).
"We were surprised that the two classical language areas were densely connected to a third area, whose presence had already been suspected but whose connections with the classical network were unknown," said lead author Marco Catani, M.D., of the Institute of Psychiatry at King's College London.
The authors dubbed this language area "Geschwind's territory" in honor of the American neurologist Norman Geschwind who championed its linguistic significance decades ago.
Language is generated and understood in the cortex, the outermost covering of the brain. Paul Broca and Carl Wernicke, 19th Century neurologists, noted that damage to specific cortical areas, which came to bear their names, produced primarily language production or language processing disorders, but not both. A large bundle of nerve fibers was found to connect Broca's and Wernicke's areas, and damage to this pathway also produced language disorders, or aphasias.
However, even in the 19th Century, there were bits of evidence that other brain areas play some role in language, though these have remained enigmatic, as scientists could not use animal models to probe language networks in the same way they could visual or movement networks in the brain.