Kammer T
Max-Planck-Institut für biologische Kybernetik, Tübingen, Germany.
Neuropsychologia. 1999 Feb;37(2):191-8. doi: 10.1016/s0028-3932(98)00093-1.
Transcranial magnetic stimulation (TMS) of the visual cortex is known to induce phosphenes and is able to suppress visual perception. To address the topographic relationship of phosphenes and transient scotomas, the visual field of 10 normal subjects was investigated using a perimetric approach. The central visual field (diameter: 20 degrees) was tested at 32 sites. Perceptual thresholds were determined by presenting 1 ms test spots flashed with varying intensity in random order. TMS was applied with a focal figure-of-eight coil placed over the inion. All subjects perceived phosphenes, mostly restricted to one of the lower quadrants within the visual field. In 13 out of 15 investigations, a magnetic stimulus triggered 100 ms after the visual target resulted in a relative scotoma with threshold changes of 8 dB or more. In 9 of 13 investigations, scotomas coincided spatially with sketches of phosphenes made by subjects in a separate test. Scotomas covered only a small percentage of the total visual field, which may explain the failure of previous studies to find perceptual suppression with the focal coil. The present result demonstrates that phosphenes evoked during TMS can serve as a guide for optimal visual stimulus alignment in neuropsychological experiments.
已知经颅磁刺激（TMS）视觉皮层可诱发光幻视并能够抑制视觉感知。为了探究光幻视与短暂性暗点的拓扑关系，采用视野检查法对10名正常受试者的视野进行了研究。在32个位点对中心视野（直径：20度）进行了测试。通过随机呈现不同强度的1毫秒测试光斑来确定感知阈值。使用放置在枕外隆凸上方的聚焦8字形线圈施加TMS。所有受试者均感知到了光幻视，大多局限于视野内的一个下象限。在15次检查中的13次中，在视觉目标出现100毫秒后触发的磁刺激导致了相对暗点，阈值变化达8分贝或更高。在13次检查中的9次中，暗点在空间上与受试者在单独测试中绘制的光幻视草图相吻合。暗点仅覆盖总视野的一小部分，这可能解释了以往研究使用聚焦线圈未能发现感知抑制的原因。目前的结果表明，TMS期间诱发的光幻视可作为神经心理学实验中最佳视觉刺激对齐的指导。
