fMRI and patient studies of remote spatial and episodic memory

回忆过去的个人经历(情景记忆)和如何在家里或附近走动(空间记忆)对日常生活都是至关重要的。如果没有情节记忆，我们就无法重新体验我们最珍视的时刻，也无法回忆起日常生活中可能需要的关键信息；如果没有空间记忆，我们实际上就会迷失。这一建议关注的是这些类型的记忆如何相互联系，以及它们在大脑中的表现方式。我们学习和保持新的情节和空间记忆的能力依赖于海马体，这是一个位于颞叶深处的结构：海马体受损会损害对最近经历的事件和空间环境的记忆。在之前NSERC资助的支持下，我和我的学生们证明，随着时间的推移，高度详细和精确的情节和空间记忆继续依赖于海马体。我们还表明，海马体的作用超越了记忆，包括想象尚未发生的详细未来情节的能力。相比之下，对非常熟悉的环境(即，主要道路和地标的骨架“地图”)的更多概括性或粗略的空间记忆似乎不依赖于海马体，而是依赖于其他大脑结构。我们发现的这些大脑结构之一位于顶叶的后部。目前这项提议的目标是研究几个相关的问题：1)海马体在支持不同类型的记忆和未来经历方面的作用只是反映了所有这些能力都共有的更基本的功能，还是这些能力在海马体的不同部分表现出来？2)海马体和顶叶如何对非常熟悉的环境的空间记忆做出贡献？3)当海马体或顶叶功能不好时，其他大脑区域是否可以“拯救”并支持空间记忆的某些方面？研究旨在通过测试记忆过去的经历、想象未来的经历以及对著名地标的外观以及它们之间的距离、方向和路线做出决定的能力来回答这些问题。我们采取了一种创新的方法，使用功能磁共振成像(FMRI)扫描专家和非专家、老年人和顶叶受损的个人，这是一种允许在参与者执行各种任务时可视化在线脑活动(血流)的技术。研究1将涉及扫描一组独特的专家，即观鸟者，他们记录过去遇到的鸟类的时间和空间位置。日记还可以作为尚未遇到的鸟类的记录，使我们能够直接比较海马体在情景记忆中的作用，以了解鸟类目击的空间或时间背景，或尚未发生的鸟类目击的未来想象。研究2涉及扫描经历海马体变化的老年人和顶叶受损的患者。这两组人有不同的记忆图谱，可以用来研究空间记忆的不同组成部分。加拿大在认知神经科学领域有着丰富的历史，并继续被视为记忆研究的国际领先者。重要的是，通过对学生进行专门培训，发展基本理论和有效应用创新技术，如用于检查大脑功能的功能磁共振成像，来保持这一地位。这项研究的发现将有助于更好地理解不同类型记忆的认知构成以及它们在人脑中的表现方式。

Remembering past personal experiences (episodic memory) and how to get around in our home or neighbourhood (spatial memory) are both crucial for daily life. Without episodic memory, we are unable to re-experience our most cherished moments or to recall critical information that may be necessary to everyday function; without spatial memory, we literally would be lost. This proposal is concerned with how these types of memories relate to one another and how they are represented in the brain. Our ability to learn and retain new episodic and spatial memories depends on the hippocampus, a structure deep in the temporal lobes: damage to the hippocampus impairs memory for recently experienced events and spatial environments. With the support of a previous NSERC grant, my students and I showed that with the passage of time, episodic and spatial memories that are highly detailed and precise continue to depend on the hippocampus. We also showed that the role of the hippocampus extends beyond memory to include the ability to imagine detailed future episodes that have not yet occurred. In contrast, more schematic or coarse spatial memories of very familiar environments (i.e., a skeletal “map” of major roads and landmarks) do not appear to depend on the hippocampus and instead rely on other brain structures. One of these brain structures that we identified is within the back portion of the parietal lobes. The goal of the current proposal is to investigate several related questions: 1) Is the role of the hippocampus in supporting different types of memories and future experiences simply a reflection of a more basic function that is common to all of these abilities, or are these abilities represented in separate parts of the hippocampus? 2) How do the hippocampus and parietal lobes contribute to spatial memories of very familiar environments? 3) Can other brain regions “come to the rescue” and support some aspects of spatial memory when the hippocampus or parietal lobes are not functioning well? Studies are designed to answer these questions by testing the ability to remember past experiences, imagine future experiences, and make decisions about well-known landmarks, including their appearance and the distances, directions, and routes between them. We take an innovative approach of scanning expert and non-experts, older adults, and individuals with damage to the parietal lobes using functional magnetic resonance imaging (fMRI), a technique that allows visualization of on-line brain activity (blood flow) as participants perform the various tasks. Study 1 will involve scanning a unique population of experts, birdwatchers, who keep journals of the time and spatial location of birds that they have encountered in the past. Journals also serve as a record of birds that have not yet been encountered, allowing us to directly compare the role of the hippocampus in episodic memory for the spatial or temporal context of bird sightings or future imagining of bird sightings that have not yet taken place. Study 2 involves scanning older adults who experience changes to the hippocampus and patients with lesions to the parietal lobes. The two groups have different memory profiles that allow for the study of different components of spatial memory. Canada has a rich history in the area of cognitive neuroscience and continues to be regarded as an international leader in memory research. It is important to maintain this status through the specialized training of students in developing basic theory and effective applications of innovative technologies such as fMRI for examining brain function. Findings from this research will lead to a greater understanding of the cognitive makeup of different types of memory and how they are represented in the human brain.