Transcranial magnetic stimulation of human frontal and parietal cortex impairs programming of periodic saccades

Transcranial magnetic stimulation (TMS) of human motor cortex typically elicits motor responses1–3. In various studies TMS has been used to examine whether or not eye-movements can also be induced by extra-cortical stimulation in humans4–8, but it has generally failed to induce such movements. The authors report findings demonstrating that saccadic trajectories can however be changed, and saccades can even be abolished when stimulation is administered within 100 msec before saccade onset. This effect is particularly marked with TMS of frontal cortex. TMS does not affect saccades when administered after they have started. It is concluded that TMS interferes with saccadic pre-programming.