More brain for language

A third language area identified in the cortex

 
Published: Tuesday 15 February 2005

a new language area has been identified in the brain following a study conducted by researchers at the Neuroimaging Sciences Institute of Psychiatry, King's College, London.

Named "Geschwind's territory" after the American neurologist who first suggested its existence in the 1960s, this is the third area in the brain to be associated with language. Its presence was revealed through the powerful new brain scanning technique, the diffusion tensor Magnetic Resonance Imaging, according to a study published in Annals of Neurology (Vol 57, No 1).

Till now, the language network of the brain was believed to consist of two areas -- Broca's area was associated with the production of language, while Wernicke's area was for comprehension. These two areas are named after 19th century neurologists Paul Broca and Carl Wernicke and are located in the cortex, the outermost layer of the brain.

Broca and Wernicke noted that damage to the cortical areas named after them, produced primary language production or language processing disorders but not both. These areas were found to be connected by a large bundle of nerve fibres and damage to this pathway also produced language disorders. Even in the 19th century, there were bits of evidence pointing to other areas in the brain, which play some role in language. Norman Geschwind also thought likewise.

King's College researchers found a separate, roundabout route that connects Broca's area with Wernicke's area via a region in the parietal lobe of the cortex. "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 are unknown," said Marco Catani, the lead researcher.

"There are clues that the parallel pathway network we found is important for the acquisition of language in childhood," added Catani. The "Geschwind's territory" is the last area in the brain to mature, the completion of its maturation coinciding with the development of reading and writing skills.

The future line of the study will be to examine the maturation of this area and its connections in the context of autism (a developmental brain disorder that typically appears during the first three years of life and affects brain areas controlling language, social interaction and abstract thought) and dyslexia (learning disability characterised by reading difficulties).

According to the researchers, these pathways appear to exist in more rudimentary forms in the brains of monkeys. This may have a bearing on the search for the evolutionary origins of language. "These data suggest that language evolved in part from changes in pre-existing networks, not through the appearance of new brain structures," pointed out Catani.

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