Spontaneous fluctuations in posterior α-band EEG activity reflect variability in excitability of human visual areas
Spontaneous fluctuations in posterior α-band EEG activity reflect variability in excitability of human visual areas
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DOI：
10.1093/cercor/bhm229
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发表时间：
2008-09-01
期刊：
影响因子：
3.7
通讯作者：
Thut, Gregor
中科院分区：
文献类型：
--
作者：
Romei, Vincenzo;Brodbeck, Verena;Thut, Gregor
神经活动随时间动态波动，这些变化已被报道具有行为意义，尽管是自发发生的。通过脑电图（EEG），已经在后部部位上识别出a波段（8 - 14 Hz）活动的波动，所述波动在逐个试验的基础上随着是否将检测到即将到来的视觉刺激而变化。这些波动被认为是视觉皮质兴奋性瞬时状态的指标。在这里，我们测试了这一假设，直接刺激人类视觉皮层通过经颅磁刺激（TMS）诱导错觉视觉感知（光幻视）在被蒙住眼睛的参与者，同时记录脑电图。我们发现，相同的TMS刺激诱发的一个神经感受器（P-是）或不（P-否）依赖于刺激前α活动。低的前刺激α带功率导致TMS可靠地诱导光幻视（P-是试验），而高的前刺激α值导致相同的TMS刺激未能唤起视觉感知（P-否试验）。进一步的分析表明，感知相关的波动α-活动/视觉皮层兴奋性的空间特异性和发生在一个循环模式的亚秒级的时间尺度。我们的数据直接链接的瞬时水平的后α-波段活动的视觉皮层兴奋性的不同状态，并表明，他们的自发波动构成了一个视觉操作模式，自动激活，即使没有视网膜输入。
Neural activity fluctuates dynamically with time, and these changes have been reported to be of behavioral significance, despite occurring spontaneously. Through electroencephalography (EEG), fluctuations in a-band (8-14 Hz) activity have been identified over posterior sites that covary on a trial-by-trial basis with whether an upcoming visual stimulus will be detected or not. These fluctuations are thought to index the momentary state of visual cortex excitability. Here, we tested this hypothesis by directly exciting human visual cortex via transcranial magnetic stimulation (TMS) to induce illusory visual percepts (phosphenes) in blindfolded participants, while simultaneously recording EEG. We found that identical TMS-stimuli evoked a percept (P-yes) or not (P-no) depending on prestimulus alpha-activity. Low prestimulus alpha-band power resulted in TMS reliably inducing phosphenes (P-yes trials), whereas high prestimulus alpha-values led the same TMS-stimuli failing to evoke a visual percept (P-no trials). Additional analyses indicated that the perceptually relevant fluctuations in alpha-activity/visual cortex excitability were spatially specific and occurred on a subsecond time scale in a recurrent pattern. Our data directly link momentary levels of posterior alpha-band activity to distinct states of visual cortex excitability, and suggest that their spontaneous fluctuation constitutes a visual operation mode that is activated automatically even without retinal input.