Wilson Mareike, Hecker Lukas, Joos Ellen, Aertsen Ad, Tebartz van Elst Ludger, Kornmeier Jürgen
Department of Psychiatry and Psychotherapy, Medical Center - University of Freiburg, Freiburg, Germany.
Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Front Hum Neurosci. 2023 May 30;17:1179081. doi: 10.3389/fnhum.2023.1179081. eCollection 2023.
During observation of the ambiguous Necker cube, our perception suddenly reverses between two about equally possible 3D interpretations. During passive observation, perceptual reversals seem to be sudden and spontaneous. A number of theoretical approaches postulate destabilization of neural representations as a pre-condition for reversals of ambiguous figures. In the current study, we focused on possible Electroencephalogram (EEG) correlates of perceptual destabilization, that may allow prediction of an upcoming perceptual reversal.
We presented ambiguous Necker cube stimuli in an onset-paradigm and investigated the neural processes underlying endogenous reversals as compared to perceptual stability across two consecutive stimulus presentations. In a separate experimental condition, disambiguated cube variants were alternated randomly, to exogenously induce perceptual reversals. We compared the EEG immediately before and during endogenous Necker cube reversals with corresponding time windows during exogenously induced perceptual reversals of disambiguated cube variants.
For the ambiguous Necker cube stimuli, we found the earliest differences in the EEG between reversal trials and stability trials already 1 s before a reversal occurred, at bilateral parietal electrodes. The traces remained similar until approximately 1100 ms before a perceived reversal, became maximally different at around 890 ms ( = 7.59 × 10, Cohen's = 1.35) and remained different until shortly before offset of the stimulus preceding the reversal. No such patterns were found in the case of disambiguated cube variants.
The identified EEG effects may reflect destabilized states of neural representations, related to destabilized perceptual states preceding a perceptual reversal. They further indicate that spontaneous Necker cube reversals are most probably not as spontaneous as generally thought. Rather, the destabilization may occur over a longer time scale, at least 1 s before a reversal event, despite the reversal event as such being perceived as spontaneous by the viewer.
在观察双稳态内克尔立方体时，我们的感知会在两种大致同样可能的三维解释之间突然反转。在被动观察期间，感知反转似乎是突然且自发的。许多理论方法假定神经表征的不稳定是双稳态图形反转的前提条件。在当前研究中，我们聚焦于感知不稳定可能的脑电图（EEG）相关指标，这些指标或许能预测即将发生的感知反转。
我们以起始范式呈现双稳态内克尔立方体刺激，并研究与连续两次刺激呈现中的感知稳定性相比，内源性反转背后的神经过程。在一个单独的实验条件下，明确的立方体变体随机交替呈现，以外源性诱导感知反转。我们将内源性内克尔立方体反转之前及期间的脑电图与明确的立方体变体在外源性诱导感知反转期间的相应时间窗进行了比较。
对于双稳态内克尔立方体刺激，我们发现在反转试验和稳定试验之间，脑电图最早的差异在反转发生前1秒就已出现在双侧顶叶电极处。这些痕迹在感知到的反转前约1100毫秒一直保持相似，在约890毫秒时差异最大（t = 7.59×10，科恩d值 = 1.35），并且在反转前的刺激消失前不久一直保持不同。在明确的立方体变体的情况下未发现此类模式。
所确定的脑电图效应可能反映了神经表征的不稳定状态，这与感知反转之前的不稳定感知状态相关。它们进一步表明，自发的内克尔立方体反转很可能并不像通常认为的那样自发。相反，这种不稳定可能在更长的时间尺度上发生，至少在反转事件前1秒，尽管观众会觉得反转事件本身是自发的。
