Kornmeier Jürgen, Bach Michael
Elektrophysiologisches Labor, Universität-Augenklinik Freiburg, Freiburg, Germany.
Psychophysiology. 2004 Jan;41(1):1-8. doi: 10.1046/j.1469-8986.2003.00126.x.
Normally we experience the visual world as stable. Ambiguous figures provide a fascinating exception: On prolonged inspection, the "Necker cube" undergoes a sudden, unavoidable reversal of its perceived front-back orientation. What happens in the brain when spontaneously switching between these equally likely interpretations? Does neural processing differ between an endogenously perceived reversal of a physically unchanged ambiguous stimulus and an exogenously caused reversal of an unambiguous stimulus? A refined EEG paradigm to measure such endogenous events uncovered an early electrophysiological correlate of this spontaneous reversal, a negativity beginning at 160 ms. Comparing across nine electrode locations suggests that this component originates in early visual areas. An EEG component of similar shape and scalp distribution, but 50 ms earlier, was evoked by an external reversal of unambiguous figures. Perceptual disambiguation seems to be accomplished by the same structures that represent objects per se, and to occur early in the visual stream. This suggests that low-level mechanisms play a crucial role in resolving perceptual ambiguity.
通常情况下，我们所体验到的视觉世界是稳定的。模糊图形则提供了一个引人入胜的例外情况：长时间观察时，“内克尔立方体”会突然、不可避免地发生其前后感知方向的反转。当在这些同样可能的解释之间自发切换时，大脑中会发生什么？在物理上未改变的模糊刺激的内源性感知反转与明确刺激的外源性引起的反转之间，神经处理过程是否存在差异？一种用于测量此类内源性事件的精细脑电图范式揭示了这种自发反转的早期电生理相关物，即从160毫秒开始的负电位。在九个电极位置进行比较表明，该成分起源于早期视觉区域。由明确图形的外部反转诱发的是一个形状和头皮分布相似但早50毫秒的脑电图成分。感知解歧似乎是由表征物体本身的相同结构完成的，并且发生在视觉信息流的早期。这表明低级机制在解决感知模糊性方面起着关键作用。
