Gurel Seref Can, Castelo-Branco Miguel, Sack Alexander T, Duecker Felix
Brain Stimulation and Cognition Group, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, Netherlands.
Maastricht Brain Imaging Center, Maastricht, Netherlands.
Front Neurosci. 2018 Dec 14;12:944. doi: 10.3389/fnins.2018.00944. eCollection 2018.
The frontal eye fields (FEFs) are core nodes of the oculomotor system contributing to saccade planning, control, and execution. Here, we aimed to reveal hemispheric asymmetries between left and right FEF in both voluntary and reflexive saccades toward horizontal and vertical targets. To this end, we applied fMRI-guided continuous theta burst stimulation (cTBS) over either left or right FEF and assessed the consequences of this disruption on saccade latencies. Using a fully counterbalanced within-subject design, we measured saccade latencies before and after the application of cTBS in eighteen healthy volunteers. In general, saccade latencies on both tasks were susceptible to our experimental manipulations, that is, voluntary saccades were slower than reflexive saccades, and downward saccades were slower than upward saccades. Contrary to our expectations, we failed to reveal any TMS-related effects on saccade latencies, and Bayesian analyses provided strong support in favor of a TMS null result for both tasks. Keeping in mind the interpretative challenges of null results, we discuss possible explanations for this absence of behavioral TMS effects, focusing on methodological differences compared to previous studies (task parameters and online vs. offline TMS interventions). We also speculate about what our results might reveal about the functional role of FEF.
额叶眼区（FEFs）是眼球运动系统的核心节点，有助于扫视的计划、控制和执行。在此，我们旨在揭示在向水平和垂直目标进行自主和反射性扫视时，左右额叶眼区之间的半球不对称性。为此，我们在左侧或右侧额叶眼区应用功能磁共振成像引导的连续theta爆发刺激（cTBS），并评估这种干扰对扫视潜伏期的影响。采用完全平衡的被试内设计，我们测量了18名健康志愿者在应用cTBS前后的扫视潜伏期。总体而言，两项任务中的扫视潜伏期均易受我们实验操作的影响，即自主扫视比反射性扫视慢，向下扫视比向上扫视慢。与我们的预期相反，我们未能揭示任何与经颅磁刺激（TMS）相关的对扫视潜伏期的影响，贝叶斯分析为两项任务的TMS无效结果提供了有力支持。牢记无效结果的解释挑战，我们讨论了这种行为TMS效应缺失的可能解释，重点关注与先前研究相比的方法学差异（任务参数以及在线与离线TMS干预）。我们还推测了我们的结果可能揭示的额叶眼区的功能作用。
