Repetitive transcranial magnetic stimulation of the dominant hemisphere can disrupt visual naming in temporal lobe epilepsy patients.

We used repetitive transcranial magnetic stimulation (rTMS) to study visual naming in 14 patients with temporal lobe epilepsy. Ten had left hemisphere language by Wada testing and all experienced speech arrest with rTMS of the motor speech area in the left frontal lobe. One left-hander had speech arrest with stimulation of sites on both sides. Subjects were asked to name pictures or read words presented on a computer monitor. rTMS was delivered on half of the trials. Stimulation sites were the motor speech area in the left frontal lobe, the mirror site on the right, and the left and right mid superior and posterior temporal lobes. rTMS at left hemisphere sites caused more naming errors than did right hemisphere rTMS. All individual subjects, except two who had temporal lobe resections and the one with bilateral speech arrest, produced more naming errors with rTMS of left hemisphere sites. There was no significant effect on word reading. rTMS at the left hemisphere and right frontal sites produced reductions in reaction time for picture naming, but not for word reading. This was observed for both correct and incorrect responses. This study shows that left hemisphere rTMS can disrupt visual naming selectively.