Brain's language center has multiple roles

A century and a half ago, French physician Pierre Paul Broca found that patients with damage to part of the brain's frontal lobe were unable to speak more than a few words. Later dubbed Broca's area, this region is believed to be critical for speech production and some aspects of language comprehension.

However, in recent years neuroscientists have observed activity in Broca's area when people perform cognitive tasks that have nothing to do with language, such as solving math problems or holding information in working memory. Those findings have stimulated debate over whether Broca's area is specific to language or plays a more general role in cognition.

A new study from MIT may help resolve this longstanding question. The researchers, led by Nancy Kanwisher, the Walter A. Rosenblith Professor of Cognitive Neuroscience, found that Broca's area actually consists of two distinct sub-units. One of these focuses selectively on language processing, while the other is part of a brainwide network that appears to act as a central processing unit for general cognitive functions.

''I think we've shown pretty convincingly that there are two distinct bits that we should not be treating as a single region, and perhaps we shouldn't even be talking about 'Broca's area' because it's not a functional unit,'' says Evelina Fedorenko, a research scientist in Kanwisher's lab and lead author of the new study, which recently appeared in the journal Current Biology.

Kanwisher and Fedorenko are members of MIT's Department of Brain and Cognitive Sciences and the McGovern Institute for Brain Research. John Duncan, a professor of neuroscience at the Cognition and Brain Sciences Unit of the Medical Research Council in the United Kingdom, is also an author of the paper.

A general role
Broca's area is located in the left inferior frontal cortex, above and behind the left eye. For this study, the researchers set out to pinpoint the functions of distinct sections of Broca's area by scanning subjects with functional magnetic resonance imaging (fMRI) as they performed a variety of cognitive tasks.