The subiculum: a key interface between scene representation and event memory?

当我们回忆事件时，我们经常会想到事件发生的具体地点，通常是生动的细节。这些心理图像通常不是像照片那样的单一快照，而是更完整和灵活的东西，我们可以想象不同的视角，环境的空间布局以及该环境中物体之间的关系。出于这个原因，了解不同的大脑区域如何处理和整合空间信息，如场景，到事件中，对于理解人类记忆以及它如何在衰老障碍中受到影响至关重要。其中一个关键区域是下托，它构成海马结构的一部分。根据动物研究，下托在大脑中具有特殊的位置，使参与记忆的区域的分布式网络能够进行通信。还有越来越多的证据表明，随着年龄的增长，这个区域非常脆弱，并且在阿尔茨海默病等疾病的早期受到影响。直到最近，研究下托一直是一个挑战，因为它的大小和在大脑中的位置使得使用传统的成像技术很难研究。在这个项目中，我们将通过最先进的高分辨率大脑扫描方法来解决这个问题，这些方法将与新的认知任务相结合，使我们能够研究下托如何通过与扩展的大脑网络的连接来支持场景感知和记忆。这个项目建立在我们之前的工作基础上，我们发现下托对于区分不同的场景至关重要，但对于其他复杂的视觉刺激，如人脸，则不是如此。我们的第一个目标是更好地了解人类下托的解剖连接，通过对动物的研究。我们将联合收割机结合结构和功能脑成像来“绘制”人脑中下托是如何连接的，并将此连接图与使用开源数据集在猴子中看到的连接图进行比较。我们还将应用一种称为图论的数学方法，看看下托是否像动物研究预测的那样，在扩展的记忆网络中充当“枢纽”。使用这种方法，我们可以调查如何虚拟“关闭”的下托，相对于其他海马子区域，影响在扩展的记忆network.Our的第二个目标是使用高分辨率的功能脑成像，以调查的精确作用下托在代表场景的信息结构之间的通信。在第一个任务中，参与者将被要求判断两个视图是否来自同一位置，这允许我们询问下托是否将场景的不同视图结合在一起（整合），或者在感知过程中将它们区分开来（区分）。在第二个任务中，我们将在扫描仪中使用虚拟现实任务，以观察经验如何塑造下托中的“整合”场景表征--下托被认为是记忆的中心。最后，基于我们的第二个目标，我们将探索下托在场景处理中的作用如何与日常事件记忆相联系。为了做到这一点，参与者将在扫描仪中观看一部电影，然后尽可能详细地回忆他们所记得的内容。我们将测试是否下托，相对于其他海马子区域，在电影叙事，被称为“事件边界”的大的变化作出反应。事件边界由我们周围世界的变化触发，并允许我们将日常经历分割成记忆中的离散“块”。通过将事件边界标记为空间或非空间，我们可以看到这种大脑活动是否由空间信息驱动（例如，该项目将对人类记忆的神经解剖学产生新的见解，测试动物的研究结果如何推广到人类，并提供有关场景和事件记忆的关键大脑网络的独特知识。

When we remember events, we often bring to mind the specific location in which that event took place, often in vivid detail. These mental images are not usually single snapshots, like photographs, but something more integrated and flexible, where we can imagine different viewpoints, the spatial layout of an environment, and the relationship between objects in that environment. For this reason, understanding how different brain regions process and integrate spatial information, such as scenes, into events, is vital for understanding human memory and how it is affected in disorders of ageing. One such critical region is the subiculum, which forms part of the hippocampal formation. According to animal studies, the subiculum has a privileged position in the brain, enabling a distributed network of regions involved in memory to communicate. There is also growing evidence that this region is highly vulnerable as we age, and affected early on in disorders such as Alzheimer's disease. Until recently it has been challenging to study the subiculum as its size and position in the brain makes it difficult to investigate using conventional imaging techniques. In this project, we will address this problem via state-of-the-art high-resolution brain scanning methods, which will be combined with novel cognitive tasks, allowing us to examine how the subiculum, via its connectivity with an extended brain network, supports scene perception and memory. This project builds on our previous work, where we found that the subiculum was critical for telling apart different scenes, but not other complex visual stimuli, such as faces. Our first aim is to better understand the anatomical connectivity of the human subiculum, informed by work on animals. We will combine both structural and functional brain imaging to 'map out' how the subiculum is connected in the human brain, and compare this connectivity map to that seen in monkeys using an open-source dataset. We will also apply a mathematical approach, called graph theory, to see if the subiculum acts as a 'hub' in an extended memory network, as predicted from animal studies. Using this approach, we can investigate how virtually "switching off" the subiculum, relative other hippocampal sub-regions, impacts on communication between structures within the extended memory network.Our second aim is to use high-resolution functional brain imaging to investigate the precise role of the subiculum in representing scene information. In the first task, participants will be asked to judge whether two views are from the same location or not, allowing us to ask whether the subiculum binds different views of a scene together (integration), or tells them apart (discrimination) during perception. In a second task, we will use a virtual-reality task in the scanner to see how 'integrated' scene representations in the subiculum - thought to be central to memory - are shaped by experience.Finally, building on our second aim, we will explore how the subiculum's role in scene processing is linked to everyday event memory. To do this, participants will watch a movie in the scanner and later recall what they remember in as much detail as possible. We will test whether the subiculum, relative to other hippocampal sub-regions, responds to large shifts in the movie narrative, known as 'event boundaries'. Event boundaries are triggered by changes in the world around us, and allow us to segment our everyday experiences into discrete 'chunks' in memory. By labelling event boundaries as either spatial or non-spatial, we can see whether this brain activity is driven by spatial information (e.g., scene changes), and how this relates to event memory.This project will generate new insights into the neuroanatomy of human memory, testing how research findings from animals generalise to humans, and providing unique knowledge about a critical brain network for scene and event memory.