Cognitive Neuroscience, Institute of Neuroscience and Medicine (INM-3), Research Center Jülich, Jülich 52425, Germany
Cognitive Neuroscience, Institute of Neuroscience and Medicine (INM-3), Research Center Jülich, Jülich 52425, Germany.
J Neurosci. 2020 May 27;40(22):4410-4417. doi: 10.1523/JNEUROSCI.2437-19.2020. Epub 2020 Apr 29.
Neural activation in the early visual cortex (EVC) reflects the perceived rather than retinal size of stimuli, suggesting that feedback possibly from extrastriate regions modulates retinal size information in EVC. Meanwhile, the lateral occipital cortex (LOC) has been suggested to be critically involved in object size processing. To test for the potential contributions of feedback modulations on size representations in EVC, we investigated the dynamics of relevant processes using transcranial magnetic stimulation (TMS). Specifically, we briefly disrupted the neural activity of EVC and LOC at early, intermediate, and late time windows while participants performed size judgment tasks in either an illusory or neutral context. TMS over EVC and LOC allowed determining whether these two brain regions are relevant for generating phenomenological size impressions. Furthermore, the temporal order of TMS effects allowed inferences on the dynamics of information exchange between the two areas. Particularly, if feedback signals from LOC to EVC are crucial for generating altered size representations in EVC, then TMS effects over EVC should be observed simultaneously or later than the effects following LOC stimulation. The data from 20 humans (13 females) revealed that TMS over both EVC and LOC impaired illusory size perception. However, the strongest effects of TMS applied over EVC occurred later than those of LOC, supporting a functionally relevant feedback modulation from LOC to EVC for scaling size information. Our results suggest that context integration and the concomitant change of perceived size require LOC and result in modulating representations in EVC via recurrent processing. How we perceive an object's size is not entirely determined by its physical size or the size of its retinal representation but also the spatial context. Using transcranial magnetic stimulation, we investigated the role of the early visual cortex (EVC) and the higher-level visual area, lateral occipital cortex (LOC), known to be critically involved in object processing, in transforming an initial retinal representation into one that reflects perceived size. Transcranial magnetic stimulation altered size perception earlier over LOC compared with EVC, suggesting that context integration and the concomitant change in perceived size representations in EVC rely on feedback from LOC.
早期视觉皮层 (EVC) 的神经激活反映的是感知到的而不是刺激的视网膜大小，这表明反馈（可能来自外侧枕叶皮层）调节了 EVC 中的视网膜大小信息。同时，外侧枕叶皮层 (LOC) 被认为在物体大小处理中起着至关重要的作用。为了测试反馈调节对 EVC 中大小表示的潜在贡献，我们使用经颅磁刺激 (TMS) 研究了相关过程的动态。具体来说，我们在参与者在幻觉或中性背景下进行大小判断任务时，在早期、中期和晚期时间窗口短暂地破坏了 EVC 和 LOC 的神经活动。EVC 和 LOC 的 TMS 允许确定这两个大脑区域是否与产生现象学大小印象有关。此外，TMS 效应的时间顺序允许推断两个区域之间信息交换的动态。特别是，如果来自 LOC 的反馈信号对于在 EVC 中产生改变的大小表示至关重要，那么 EVC 上的 TMS 效应应该与 LOC 刺激后的效应同时或之后观察到。来自 20 名人类（13 名女性）的数据显示，EVC 和 LOC 的 TMS 都损害了幻觉大小感知。然而，EVC 上 TMS 的最强影响发生在 LOC 之后，这支持了 LOC 到 EVC 的功能相关反馈调节对于大小信息的缩放。我们的结果表明，上下文整合和随之而来的感知大小变化需要 LOC，并通过递归处理在 EVC 中调节表示。我们如何感知物体的大小不仅取决于其物理大小或视网膜表示的大小，还取决于空间上下文。使用经颅磁刺激，我们研究了早期视觉皮层 (EVC) 和外侧枕叶皮层 (LOC) 的作用，已知这两个区域在物体处理中起着关键作用，它们将初始的视网膜表示转换为反映感知大小的表示。与 EVC 相比，TMS 更早地改变了 LOC 上的大小感知，这表明上下文整合和 EVC 中感知大小表示的伴随变化依赖于来自 LOC 的反馈。
