de Graaf T A, Duecker F, Stankevich Y, Ten Oever S, Sack A T
Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands; Maastricht Brain Imaging Centre, Maastricht, The Netherlands.
Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands; Maastricht Brain Imaging Centre, Maastricht, The Netherlands.
Brain Stimul. 2017 Jul-Aug;10(4):828-835. doi: 10.1016/j.brs.2017.04.127. Epub 2017 May 3.
Voluntarily opening or closing our eyes results in fundamentally different input patterns and expectancies. Yet it remains unclear how our brains and visual systems adapt to these ocular states.
OBJECTIVE/HYPOTHESIS: We here used transcranial magnetic stimulation (TMS) to probe the excitability of the human visual system with eyes open or closed, in the complete absence of visual inputs.
Combining Bayesian staircase procedures with computer control of TMS pulse intensity allowed interleaved determination of phosphene thresholds (PT) in both conditions. We measured parieto-occipital EEG baseline activity in several stages to track oscillatory power in the alpha (8-12 Hz) frequency-band, which has previously been shown to be inversely related to phosphene perception.
Since closing the eyes generally increases alpha power, one might have expected a decrease in excitability (higher PT). While we confirmed a rise in alpha power with eyes closed, visual excitability was actually increased (PT was lower) with eyes closed.
This suggests that, aside from oscillatory alpha power, additional neuronal mechanisms influence the excitability of early visual cortex. One of these may involve a more internally oriented mode of brain operation, engaged by closing the eyes. In this state, visual cortex may be more susceptible to top-down inputs, to facilitate for example multisensory integration or imagery/working memory, although alternative explanations remain possible.
主动睁开或闭上眼睛会导致根本不同的输入模式和预期。然而，我们的大脑和视觉系统如何适应这些眼部状态仍不清楚。
目的/假设：我们在此使用经颅磁刺激（TMS）在完全没有视觉输入的情况下，探究人眼睁开或闭合时视觉系统的兴奋性。
将贝叶斯阶梯程序与TMS脉冲强度的计算机控制相结合，允许在两种情况下交错确定光幻视阈值（PT）。我们在几个阶段测量顶枕部脑电图基线活动，以追踪α（8 - 12赫兹）频段的振荡功率，此前已表明该频段与光幻视感知呈负相关。
由于闭上眼睛通常会增加α功率，人们可能预期兴奋性会降低（PT更高）。虽然我们证实闭眼时α功率会升高，但实际上闭眼时视觉兴奋性增加了（PT更低）。
这表明，除了振荡α功率外，其他神经元机制也会影响早期视觉皮层的兴奋性。其中之一可能涉及通过闭眼参与的更以内向为导向的大脑运作模式。在这种状态下，视觉皮层可能更容易受到自上而下的输入影响，例如促进多感官整合或意象/工作记忆，尽管也可能有其他解释。
