Magnetically induced phosphenes in sighted, blind and blindsighted observers

Direct stimulation of visual cortex can produce illusory flashes of light, called phosphenes. Here we describe the spatial and motion properties of ph osphenes produced by transcranial magnetic stimulation in normal subjects a nd in two subjects with peripheral or cortical blindness. The totally retin ally blind subject experienced normal phosphenes, apart from their concentr ation in the centre of the visual field, whereas the hemianopic subject, la cking area VI, did not experience phosphenes when his surviving extrastriat e visual areas were stimulated. In the absence of VI, magnetically induced activity was unable to generate a conscious visual percept in the field def ect. NeuroReport 11:3269-3273 (C) 2000 Lippincott Williams & Wilkins.