Broca's aphasia · Grey Matter

Broca's aphasia is a disorder of language production after damage to the left frontal lobe, in which speech becomes slow, effortful and stripped of grammar while the understanding of everyday conversation is relatively preserved.

Broca's aphasia. Broca's aphasia is a disorder of language production after damage to the left frontal lobe, in which speech becomes slow, effortful and stripped of grammar while the understanding of everyday conversation is relatively preserved.

A typical patient speaks in short phrases of content words (walk dog... park), dropping articles, endings and small function words, with great effort and often with distorted articulation. Naming and repetition are impaired, and writing usually mirrors speech. Comprehension of simple sentences is good, but sentences whose meaning depends on grammar alone (the boy was hit by the girl) are often misunderstood. Patients are usually aware of their errors and frustrated by them, unlike in Wernicke's aphasia.

The lesion is usually larger than Broca's area. Lasting Broca's aphasia needs damage to the inferior frontal gyrus together with the insula, the underlying white matter and nearby cortex; damage confined to Broca's area tends to produce a milder, transient disturbance.

Weakness of the right arm and face often accompanies it, because the same arterial territory supplies the nearby motor cortex.

Speech therapy helps, and some patients can sing familiar lyrics they cannot speak, which is the basis of melodic intonation therapy.

Questions: If Broca's area makes speech, why does a lesion confined to it rarely cause lasting Broca's aphasia? Speech production is a network, and Broca's area (left Brodmann areas 44 and 45) is one node in it, beside the insula, the motor and premotor cortex for the mouth, and the white matter that links them to the temporal lobe. In 1978 Mohr and colleagues found that a stroke limited to Broca's area produced mutism or effortful speech that recovered within weeks, while the full, lasting syndrome followed large lesions of the territory around it. Even the brains of Broca's own patients, scanned in 2007, showed damage reaching well beyond the area that carries his name.