April 26 : A re-examination of two human brains originally diagnosed by French surgeon and anatomist Paul Broca in 1861 to deduce the region in the brain responsible for language, has shed fresh light on the part of the brain governing speech.

Broca had described two patients who had lost the ability to speak. One patient, Lelong, could produce only five words, and the second, Leborgne, could utter only one sound — “tan”.

Examination of their brains after their death revealed damage to a region in the frontal area on the left side, which came to be known as Broca’s area, and is now thought to be the brain’s speech-processing centre.

But now a re-examination of the preserved brains by Nina Dronkers, of the VA Northern California Health Care System in Martinez, and her colleagues, has revealed extensive damage in an area much larger than the region considered to be Broca’s area.

“We were noticing that what people were calling Broca’s area, encompassed large areas of the frontal lobe. The scans show that neither of the old brains had damage that affected the whole region now known as Broca’s area, but damage also stretched far into other regions beyond this spot,” Nature quoted Dronkers as saying.

“Broca realized this at the time, and noted that the areas of damage were different in the two patients. But his conception of the area involved in speech processing has become simplified by others over time,” she added.

According to her, this misplaced focus could lead to problems when diagnosing people with language impairments.

“By assuming that only one small area of the brain is responsible for language, clinicians might overlook other regions involved in speech production. In other words, focusing too heavily on Broca’s area could be missing the point,” she said.

“There’s a tendency for researchers to see activation in somewhere like Broca’s area and to say ‘oh well, we’re tapping into a language area’,” added Joseph Devlin, a neuroscientist at the University of Oxford, UK, who images language networks in the brain.

According to Dronkers, newer imaging techniques might help researchers discover what Broca was unable to see, and investigate other regions of the brain that may be important in language processing, but which are not detected by magnetic resonance imaging, such as the tracts of white matter that connect areas of grey matter. The findings appear online in the journal Brain. (ANI)