Recent neuroimaging studies in blind persons show that the occipital cortex, including the primary visual cortex (V1), is active during language-related and verbal-memory tasks. No studies, however, have identified a causal link between early visual cortex activity and successful performance on such tasks. We show here that repetitive transcranial magnetic stimulation (rTMS) of the occipital pole reduces accuracy on a verb-generation task in blind subjects, but not in sighted controls. An analysis of error types revealed that the most common error produced by rTMS was semantic; phonological errors and interference with motor execution or articulation were rare. Thus, in blind persons, a transient 'virtual lesion' of the left occipital cortex interferes with high-level verbal processing.
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We thank C. Wu for help with MRI acquisition; C. Poletto for help and advice on the recording and auditory equipment; D. Glasser, A. Dorsch and M. Skupinsky for research assistance; and our dedicated blind and sighted subjects. A.F. is supported by a grant (Fl 379/1-1) from the Deutsche Forschungsgemeinschaft, Bonn. E.Z. was supported by McDonnell—Pew Foundation grant JSMF#220020046 and A.A. by a Horowitz fellowship.