A patient who could only say 'tan', and another who spoke fluently but made no sense: how two 19th-century neurologists discovered that language lives largely in the left hemisphere.
History of Neuroscience
Beginner
Broca, Wernicke and the Language Areas
The Editors
May 17, 2026
3 min read
In plain English
In 1861 Paul Broca examined the brain of a man who could understand speech but only say one syllable, and found damage in a specific spot on the left side. A few years later Carl Wernicke found a different spot whose damage left people speaking fluently but without sense. These were the first strong proofs that brain areas specialise.
Beginner level: No background needed. Everyday language, everyday examples — the place to start.
Concepts to know first
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"Tan"
In April 1861 the French surgeon and anthropologist Paul Broca (1824–1880) met a patient named Louis Victor Leborgne at the Bicêtre hospital in Paris. Leborgne had lost the ability to speak more than two decades earlier; he could understand what was said to him, but the only syllable he could produce was "tan" — which became his nickname. He died days later, and Broca examined his brain. He found a lesion in the left frontal lobe.
Over the next few years, Broca collected more cases and in 1865 made the bold claim that "we speak with the left hemisphere". The region — the back of the left inferior frontal gyrus — is now called Broca's area, and the condition, in which speech production is laboured and halting while comprehension is relatively spared, is called Broca's (expressive) aphasia. Leborgne's brain is still preserved in Paris; modern MRI scans show the damage extended deeper than Broca reported.
The other side of language
In 1874 the 26-year-old German neurologist Carl Wernicke (1848–1905) described patients with the opposite problem: they spoke fluently, with normal rhythm, but their words were jumbled or meaningless and they understood little of what was said to them. Their damage lay further back, in the left temporal lobe — Wernicke's area.
Wernicke also proposed that the two areas are linked by a bundle of fibres (later identified as the arcuate fasciculus), and predicted that damaging the link would cause a third kind of aphasia, conduction aphasia, with trouble repeating words. That was confirmed — an early triumph of a network model of brain function.
The modern picture
Today we know language is far more distributed: it involves frontal, temporal and parietal regions, the basal ganglia and cerebellum, and works with similar regions in sign languages. Still, the left-hemisphere bias holds for most people — about 95% of right-handers and roughly 70% of left-handers.
Everyday examples & things to try
Picture it
Two kinds of broken sentence
Broca's aphasia: "Walk... dog... park... yesterday." — the meaning is there but the words are hard to get out. Wernicke's aphasia: "Well I went to the thing and the clam with the over there they made it ready" — the words flow but the meaning is lost.
Key takeaways
- Broca (1861) linked loss of speech production to damage in the left frontal lobe.
- Wernicke (1874) linked fluent but meaningless speech to the left temporal lobe.
- Language relies on a left-lateralised network, not just two spots.
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