Transcranial magnetic stimulation in the visual system. II. Characterization of induced phosphenes and scotomas
Transcranial magnetic stimulation in the visual system. II. Characterization of induced phosphenes and scotomas
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DOI：
10.1007/s00221-004-1992-0
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发表时间：
2005-01-01
影响因子：
2
通讯作者：
Grodd, W
中科院分区：
文献类型：
--
作者：
Kammer, T;Puls, K;Grodd, W
经颅磁刺激（TMS）在枕极上应用时会诱导光幻视并破坏视觉感知。其潜在的机制和涉及的大脑结构仍然不清楚。在本研究的第一部分中，我们表明TMS的掩蔽效应不同于光掩蔽的心理测量功能。在这里，我们调查的出现光幻视的周长测量。线圈的位置进行了测量与立体定向定位装置，刺激部位的特征在于在四个科目的基础上，个人的视网膜定位图与功能性磁共振成像测量。发现光幻视阈值低于诱导视觉掩蔽所需的刺激强度0.59倍。它们覆盖了在较高刺激强度下发生视觉抑制的视野段。在受刺激半球对侧象限的下视野中发现光幻视和短暂暗点。它们可以从枕极上方的一大片区域诱发。光幻视的轮廓和纹理保持相当稳定的不同线圈的位置超过一个半球，并没有改变的视网膜病变的不同视觉领域的线圈集中。它们不能只与特定功能定义的视觉区域相关。最有可能的是，在V1背侧部分接近其终端的视辐射和从V2和V3返回V1的背投射纤维都产生了光幻视和暗点。
Transcranial magnetic stimulation (TMS) induces phosphenes and disrupts visual perception when applied over the occipital pole. Both the underlying mechanisms and the brain structures involved are still unclear. In the first part of this study we show that the masking effect of TMS differs to masking by light in terms of the psychometric function. Here we investigate the emergence of phosphenes in relation to perimetric measurements. The coil positions were measured with a stereotactic positioning device, and stimulation sites were characterized in four subjects on the basis of individual retinotopic maps measured by with functional magnetic resonance imaging. Phosphene thresholds were found to lie a factor of 0.59 below the stimulation intensities required to induce visual masking. They covered the segments in the visual field where visual suppression occurred with higher stimulation intensity. Both phosphenes and transient scotomas were found in the lower visual field in the quadrant contralateral to the stimulated hemisphere. They could be evoked from a large area over the occipital pole. Phosphene contours and texture remained quite stable with different coil positions over one hemisphere and did not change with the retinotopy of the different visual areas on which the coil was focused. They cannot be related exclusively to a certain functionally defined visual area. It is most likely that both the optic radiation close to its termination in the dorsal parts of V1 and back-projecting fibers from V2 and V3 back to V1 generate phosphenes and scotomas.