The human brain continuously processes streams of visual input. Yet, a single image typically triggers neural responses that extend beyond 1s. To understand how the brain encodes and maintains successive images, we analyzed with electroencephalography the brain activity of human subjects while they watched ~5000 visual stimuli presented in fast sequences. First, we confirm that each stimulus can be decoded from brain activity for ~1s, and we demonstrate that the brain simultaneously represents multiple images at each time instant. Second, we source localize the corresponding brain responses in the expected visual hierarchy and show that distinct brain regions represent, at each time instant, different snapshots of past stimulations. Third, we propose a simple framework to further characterize the dynamical system of these traveling waves. Our results show that a chain of neural circuits, which each consist of (1) a hidden maintenance mechanism and (2) an observable update mechanism, accounts for the dynamics of macroscopic brain representations elicited by visual sequences. Together, these results detail a simple architecture explaining how successive visual events and their respective timings can be simultaneously represented in the brain.

SIGNIFICANCE STATEMENT Our retinas are continuously bombarded with a rich flux of visual input. Yet, how our brain continuously processes such visual streams is a major challenge to neuroscience. Here, we developed techniques to decode and track, from human brain activity, multiple images flashed in rapid succession. Our results show that the brain simultaneously represents multiple successive images at each time instant by multiplexing them along a neural cascade. Dynamical modeling shows that these results can be explained by a hierarchy of neural assemblies that continuously propagate multiple visual contents. Overall, this study sheds new light on the biological basis of our visual experience.

人脑不断地处理视觉输入流。然而，单个图像通常会触发超过 1 秒的神经反应。为了了解大脑如何编码和维护连续图像，我们使用脑电图分析了人类受试者在观看以快速序列呈现的约 5000 个视觉刺激时的大脑活动。首先，我们确认每个刺激都可以从大脑活动中解码约 1 秒，并且我们证明大脑在每个时刻同时表示多个图像。其次，我们在预期的视觉层次中定位相应的大脑反应，并表明不同的大脑区域在每个时刻代表过去刺激的不同快照。第三，我们提出了一个简单的框架来进一步表征这些行波的动力系统。我们的结果表明，一个神经回路链，每个都由（1）一个隐藏的维护机制和（2）一个可观察的更新机制组成，解释了视觉序列引起的宏观大脑表征的动态。总之，这些结果详细说明了一个简单的架构，解释了如何在大脑中同时表示连续的视觉事件及其各自的时间。

重要性声明我们的视网膜不断受到大量视觉输入的冲击。然而，我们的大脑如何持续处理这些视觉流是神经科学面临的一项重大挑战。在这里，我们开发了技术来解码和跟踪从人类大脑活动中快速连续闪烁的多个图像。我们的结果表明，大脑通过沿神经级联对它们进行多路复用，在每个时刻同时表示多个连续图像。动态建模表明，这些结果可以通过连续传播多个视觉内容的神经组件层次结构来解释。总的来说，这项研究揭示了我们视觉体验的生物学基础。