INDUCTION OF VISUAL EXTINCTION BY RAPID-RATE TRANSCRANIAL MAGNETIC STIMULATION OF PARIETAL LOBE

We used repetitive, rapid-rate transcranial magnetic stimulation (rTMS ) for the noninvasive study of visual attention in humans. Six right-h anded volunteers completed eight blocks of 20 single- and 10 double-vi sual-stimulus trials. The visual stimulus was a single asterisk on the right or left side of a computer screen or two asterisks presented si multaneously. The subject had to respond to the stimulus by pressing t he right or left response key or both keys simultaneously. During six of the blocks, we applied focal rTMS in trains of five pulses at 25 Hz and 115% of the subject's motor threshold intensity to scalp position s O1, O2, P3, P4, T5, or T6. Occipital rTMS led to a large number of m isses of the contralateral asterisk regardless of whether a single or double stimulus was presented. Parietal rTMS did not induce misses of single stimuli but led to a large number of misses of the contralatera l asterisk in the double-stimulus condition. The effects of temporal r TMS were inconsistent. We conclude that rTMS to the occipital lobe cau ses a sensory detection block, whereas rTMS to the parietal lobe can i nduce selective extinction of contralateral visual stimuli during a si multaneous double stimulus.