Department of Psychology, University of Cambridge, Cambridge CB2 3EB, United Kingdom
Center for Neuroscience, University of California, Davis, California 95618.
J Neurosci. 2022 Jul 27;42(30):5956-5965. doi: 10.1523/JNEUROSCI.2045-21.2022. Epub 2022 Jun 24.
When making a turn at a familiar intersection, we know what items and landmarks will come into view. These perceptual expectations, or predictions, come from our knowledge of the context; however, it is unclear how memory and perceptual systems interact to support the prediction and reactivation of sensory details in cortex. To address this, human participants learned the spatial layout of animals positioned in a cross maze. During fMRI, participants of both sexes navigated between animals to reach a target, and in the process saw a predictable sequence of five animal images. Critically, to isolate activity patterns related to item predictions, rather than bottom-up inputs, one-fourth of trials ended early, with a blank screen presented instead. Using multivariate pattern similarity analysis, we reveal that activity patterns in early visual cortex, posterior medial regions, and the posterior hippocampus showed greater similarity when seeing the same item compared with different items. Further, item effects in posterior hippocampus were specific to the sequence context. Critically, activity patterns associated with seeing an item in visual cortex and posterior medial cortex, were also related to activity patterns when an item was expected, but omitted, suggesting sequence predictions were reinstated in these regions. Finally, multivariate connectivity showed that patterns in the posterior hippocampus at one position in the sequence were related to patterns in early visual cortex and posterior medial cortex at a later position. Together, our results support the idea that hippocampal representations facilitate sensory processing by modulating visual cortical activity in anticipation of expected items. Our visual world is a series of connected events, where we can predict what we might see next based on our recent past. Understanding the neural circuitry and mechanisms of the perceptual and memory systems that support these expectations is fundamental to revealing how we perceive and act in our world. Using brain imaging, we studied what happens when we expect to see specific visual items, and how such expectations relate to top-down memory signals. We find both visual and memory systems reflect item predictions, and moreover, we show that hippocampal activity supports predictions of future expected items. This demonstrates that the hippocampus acts to predict upcoming items, and reinstates such predictions in cortex.
当我们在熟悉的十字路口转弯时，我们知道哪些物品和地标会进入视野。这些感知期望或预测来自我们对上下文的了解；然而，目前尚不清楚记忆和感知系统如何相互作用，以支持皮层中感官细节的预测和重新激活。为了解决这个问题，人类参与者学习了放置在十字迷宫中的动物的空间布局。在 fMRI 期间，男女参与者在动物之间导航以到达目标，在此过程中看到了一系列可预测的五个动物图像。关键的是，为了分离与项目预测相关的活动模式，而不是与自上而下的输入相关的活动模式，四分之一的试验提前结束，取而代之的是呈现空白屏幕。使用多元模式相似性分析，我们发现早期视觉皮层、后内侧区域和后海马体的活动模式在看到相同项目时比看到不同项目时具有更高的相似性。此外，后海马体中的项目效应与序列上下文有关。关键的是，与在视觉皮层和后内侧皮层中看到项目相关的活动模式也与项目被期望但被省略时的活动模式有关，这表明在这些区域中重新建立了序列预测。最后，多元连通性显示，序列中一个位置的后海马体的模式与稍后位置的早期视觉皮层和后内侧皮层的模式相关。总的来说，我们的结果支持这样的观点，即海马体的表示通过在预期项目之前调制视觉皮层的活动来促进感觉处理。我们的视觉世界是一系列相互关联的事件，我们可以根据最近的过去预测我们接下来可能会看到什么。了解支持这些期望的感知和记忆系统的神经回路和机制是揭示我们如何在我们的世界中感知和行动的基础。使用脑成像，我们研究了当我们期望看到特定视觉项目时会发生什么，以及这种期望如何与自上而下的记忆信号相关。我们发现视觉和记忆系统都反映了项目预测，而且，我们还表明海马体活动支持对未来预期项目的预测。这表明海马体用于预测即将到来的项目，并在皮层中重新建立这些预测。
