Brückner Sabrina, Kammer Thomas
Department of Psychiatry, University of Ulm, Ulm, Germany.
PLoS One. 2014 Jun 10;9(6):e99429. doi: 10.1371/journal.pone.0099429. eCollection 2014.
Repetitive transcranial magnetic stimulation is usually applied to visual cortex to explore the effects on cortical excitability. Most researchers therefore concentrate on changes of phosphene threshold, rarely on consequences for visual performance. Thus, we investigated peripheral visual acuity in the four quadrants of the visual field using Landolt C optotypes before and after repetitive stimulation of the visual cortex. We applied continuous and intermittend theta burst stimulation with various stimulation intensities (60%, 80%, 100%, 120% of individual phosphene threshold) as well as monophasic and biphasic 1 Hz stimulation, respectively. As an important result, no serious adverse effects were observed. In particular, no seizure was induced, even with theta burst stimulation applied with 120% of individual phosphene threshold. In only one case stimulation was ceased because the subject reported intolerable pain. Baseline visual acuity decreased over sessions, indicating a continuous training effect. Unexpectedly, none of the applied transcranial magnetic stimulation protocols had an effect on performance: no change in visual acuity was found in any of the four quadrants of the visual field. Binocular viewing as well as the use of peripheral instead of foveal presentation of the stimuli might have contributed to this result. Furthermore, intraindividual variability could have masked the TMS- induced effects on visual acuity.
重复经颅磁刺激通常应用于视觉皮层以探究其对皮层兴奋性的影响。因此，大多数研究人员专注于光幻视阈值的变化，很少关注对视觉表现的影响。于是，我们在视觉皮层重复刺激前后，使用Landolt C视标对视野的四个象限的周边视力进行了研究。我们分别应用了不同刺激强度（个体光幻视阈值的60%、80%、100%、120%）的连续和间歇式theta爆发刺激以及单相和双相1Hz刺激。一个重要的结果是，未观察到严重的不良反应。特别是，即使使用个体光幻视阈值120%的theta爆发刺激，也未诱发癫痫发作。仅在一例中，由于受试者报告无法忍受的疼痛，刺激被停止。基线视力在各次测试中下降，表明存在持续的训练效应。出乎意料的是，所应用的任何经颅磁刺激方案均未对表现产生影响：在视野的四个象限中，视力均未发现变化。双眼观察以及使用周边而非中央凹呈现刺激可能导致了这一结果。此外，个体内变异性可能掩盖了经颅磁刺激对视敏度的影响。
