Department of Cognitive Sciences, University of California at Irvine, Irvine, California, USA.
J Neurophysiol. 2011 Oct;106(4):1734-46. doi: 10.1152/jn.00739.2010. Epub 2011 Jun 29.
Single pulses of transcranial magnetic stimulation (TMS) result in distal and long-lasting oscillations, a finding directly challenging the virtual lesion hypothesis. Previous research supporting this finding has primarily come from stimulation of the motor cortex. We have used single-pulse TMS with simultaneous EEG to target seven brain regions, six of which belong to the visual system [left and right primary visual area V1, motion-sensitive human middle temporal cortex, and a ventral temporal region], as determined with functional MRI-guided neuronavigation, and a vertex "control" site to measure the network effects of the TMS pulse. We found the TMS-evoked potential (TMS-EP) over visual cortex consists mostly of site-dependent theta- and alphaband oscillations. These site-dependent oscillations extended beyond the stimulation site to functionally connected cortical regions and correspond to time windows where the EEG responses maximally diverge (40, 200, and 385 ms). Correlations revealed two site-independent oscillations ∼350 ms after the TMS pulse: a theta-band oscillation carried by the frontal cortex, and an alpha-band oscillation over parietal and frontal cortical regions. A manipulation of stimulation intensity at one stimulation site (right hemisphere V1-V3) revealed sensitivity to the stimulation intensity at different regions of cortex, evidence of intensity tuning in regions distal to the site of stimulation. Together these results suggest that a TMS pulse applied to the visual cortex has a complex effect on brain function, engaging multiple brain networks functionally connected to the visual system with both invariant and site-specific spatiotemporal dynamics. With this characterization of TMS, we propose an alternative to the virtual lesion hypothesis. Rather than a technique that simulates lesions, we propose TMS generates natural brain signals and engages functional networks.
单次经颅磁刺激 (TMS) 会产生远程且持久的震荡，这一发现直接挑战了虚拟损伤假说。支持这一发现的先前研究主要来自于对运动皮层的刺激。我们使用单次脉冲 TMS 与同时进行的 EEG 来针对七个脑区进行刺激，其中六个脑区属于视觉系统[左、右初级视觉区 V1、对运动敏感的人类中颞叶皮层和腹侧颞叶区]，这是通过功能磁共振成像引导的神经导航确定的，以及一个顶点“对照”部位来测量 TMS 脉冲的网络效应。我们发现，视觉皮层上的 TMS 诱发电位 (TMS-EP) 主要由部位依赖性的θ和α波段震荡组成。这些部位依赖性的震荡延伸到刺激部位之外的功能连接的皮质区域，与 EEG 反应最大发散的时间窗口相对应（40、200 和 385 ms）。相关性揭示了 TMS 脉冲后约 350 ms 有两个部位独立的震荡：一个由额叶皮层携带的θ波段震荡，以及一个跨越顶叶和额叶皮层区域的α波段震荡。在一个刺激部位（右半球 V1-V3）上进行刺激强度的操作，揭示了对皮质不同区域的刺激强度的敏感性，这是刺激部位以外的区域对刺激强度进行调谐的证据。这些结果表明，施加于视觉皮层的 TMS 脉冲对大脑功能具有复杂的影响，涉及到与视觉系统功能连接的多个大脑网络，具有不变和部位特异性的时空动态。通过对 TMS 的这种描述，我们提出了对虚拟损伤假说的替代方案。我们建议 TMS 不是一种模拟损伤的技术，而是生成自然的大脑信号并参与功能网络。
