Comprehension deficits elicited by electrical stimulation of Broca's area.

We report on three patients with intractable focal seizures arising from the language-dominant left hemisphere. In the work-up prior to surgical treatment, arrays of subdural electrodes were placed over the left temporal lobe and adjacent supra-Sylvian region. Electrical stimulation of the inferior frontal cortex language region ('Broca's area') produced marked interference with language output functions including speech arrest, slowing of oral reading, paraphasia and anomia. At some cortical language sites in this region cortical stimulation also produced language comprehension deficits, particularly in response to more complex auditory verbal instructions and visual semantic material. The severe impairment of comprehension verbal information was in clear contrast with ability to process non-verbal material, which was not affected.