Center for Studies of Psychological Application and School of Psychology, South China Normal University, Guangzhou, China.
Guangdong Key Laboratory of Mental Health and Cognitive Science, South China Normal University, Guangzhou, China.
PLoS Biol. 2019 Mar 13;17(3):e3000025. doi: 10.1371/journal.pbio.3000025. eCollection 2019 Mar.
The brain uses its intrinsic dynamics to actively predict observed sensory inputs, especially under perceptual ambiguity. However, it remains unclear how this inference process is neurally implemented in biasing perception of ambiguous inputs towards the predicted percepts. The process of perceptual inference can be well illustrated by the phenomenon of bistable apparent motion in the Ternus display, in which subjective perception spontaneously alternates between element motion (EM) and group motion (GM) percepts depending on whether two consecutively presented frames are grouped over time or not. The frequency of alpha-band oscillations has long been hypothesized to gate the temporal window of perceptual grouping over time. Under this hypothesis, variation in the intrinsic alpha frequency should predict perceptual outcome of the bistable Ternus display. Moreover, we hypothesize that the perception system employs this prior knowledge on intrinsic alpha frequency to resolve perceptual ambiguity, by shifting perceptual inference towards the predicted percepts. Using electroencephalography and intracranial recordings, we showed that both between and within subjects, lower prestimulus alpha frequencies (PAFs) predicted the EM percepts since the two frames fell in the same alpha cycle and got temporally integrated, while higher PAFs predicted the GM percepts since the two frames fell in different alpha cycles. Multivariate decoding analysis between the EM percepts with lower PAFs and the GM percepts with higher PAFs further revealed a representation of the subsequently reported bistable percept in the neural signals shortly before the actual appearance of the second frame. Therefore, perceptual inference, based on variation in intrinsic PAFs, biases poststimulus neural representations by inducing preactivation of the predicted percepts. In addition, enhanced prestimulus blood-oxygen-level-dependent (BOLD) signals and network dynamics in the frontoparietal network, together with reduced prestimulus alpha power, upon perceiving the EM percepts suggest that temporal grouping is an attention-demanding process.
大脑利用其内在动力学主动预测观察到的感官输入，尤其是在感知模糊的情况下。然而，目前尚不清楚这种推断过程如何在神经上实现，将模糊输入的感知偏向于预测的感知。感知推断过程可以很好地通过 Ternus 显示器中的双稳态明显运动现象来说明，其中主观感知会根据两个连续呈现的帧是否随着时间被分组而在元素运动（EM）和组运动（GM）感知之间自发交替。α 波段振荡的频率长期以来一直被假设为随时间感知分组的时间窗口。在这个假设下，内在 α 频率的变化应该预测双稳态 Ternus 显示器的感知结果。此外，我们假设感知系统利用内在 α 频率的这种先验知识来解决感知模糊性，通过将感知推断偏向于预测的感知。使用脑电图和颅内记录，我们表明，无论是在个体之间还是在个体内部，较低的预刺激 α 频率（PAF）预测了 EM 感知，因为两个帧处于同一α周期内并且随时间整合，而较高的 PAF 预测了 GM 感知，因为两个帧处于不同的α周期内。在较低 PAF 的 EM 感知与较高 PAF 的 GM 感知之间进行的多元解码分析进一步揭示了在第二个框架实际出现之前，在神经信号中随后报告的双稳态感知的表示。因此，基于内在 PAF 变化的感知推断通过诱导预测感知的预激活来偏向于刺激后神经表示。此外，在感知 EM 感知时，额顶网络中的增强的预刺激血氧水平依赖（BOLD）信号和网络动态以及减少的预刺激α功率表明，时间分组是一个需要注意力的过程。
