Astereopsis induced by repetitive magnetic stimulation of occipital cortex.

Three healthy subjects underwent repetitive transcranial magnetic stimulation (20 Hz, 1 s) with a round oil-cooled coil held tangentially against the skull surface 3 or 4 cm above the inion, while viewing a random-dot stereogram through red-green glasses. The coil was positioned over the midline of the bilateral superior occipital lobes. All three subjects experienced loss of stereoscopic perception during stimulation. A stimulus duration of more than 0.2 s and a stimulus frequency of more than 10 Hz seem to be necessary to disrupt the cortical mechanisms involved in global stereopsis. Repetitive magnetic stimulation easily and painlessly produced a reversible disturbance in global stereopsis. The results suggest that the bilateral superior occipital cortices are involved in the perception of global stereopsis.