The brain's famous 'speech centre' is not quite what the textbooks say.
A patient who could say only one syllable, 'tan', led the French physician Paul Broca to locate speech in a patch of the left frontal lobe. It became one of neuroscience's first great maps. Modern scans of that same preserved brain, and of other patients, suggest the story is messier.
Broca's best-known patient was Louis Victor Leborgne, who by the age of 30 could barely produce any words; whatever he was asked, he answered 'tan', which became his nickname. After his death, Broca found damage on the surface of his left frontal lobe. A second patient, Lazare Lelong, who could say only five words, had a lesion in the same region. Broca concluded that speech production was localised there, a finding often described as the first anatomical proof that particular functions live in particular parts of the brain.
The region, in the frontal lobe of the dominant hemisphere, usually the left, became known as Broca's area, and the loss of fluent speech after damage there as Broca's, or expressive, aphasia. People with it typically know what they want to say but cannot get it out, producing halting 'telegraphic' speech stripped of grammar, such as 'go store... buy food', while still understanding simple sentences and noticing their own mistakes.
Since the late 1970s, though, the link has looked looser. Damage confined to Broca's area tends to cause only temporary muteness lasting a few weeks, and many people with Broca's aphasia have damage elsewhere. One engineer had a slow-growing tumour that, with its surgery, destroyed much of the region; three months later he had only minor language problems and went back to work, probably because nearby areas and the right hemisphere took over. In 2007, high-resolution MRI of Leborgne's and Lelong's preserved brains showed damage well beyond the classic zone, and that the spot Broca identified is not exactly what is now called Broca's area.
Imaging also shows the area helping with understanding complex sentences, with verbal working memory and even with interpreting other people's gestures, which has fed theories that language grew out of gesture. The emerging picture is of Broca's area as a busy hub in a wider network rather than a single speech centre. Broca's core insight, that brain regions specialise, still stands; the map just turned out to have more roads.
Source: Wikipedia — Broca's area · Text summarised from Wikipedia (CC BY-SA 4.0)
