Representation of spatial coordinate systems within posterior parietal cortex and hippocampus

为了准确地够到一个物体或从一个房间走到另一个房间，我们的大脑需要能够定位我们周围的物体并探测到我们路径上的障碍物。我们有一种惊人的能力，可以让眼睛准确地直视一个物体，比如一杯茶，并将我们的手平稳地直接移到杯子上，这是我们都认为理所当然的事情。然而，这种能力需要巨大的计算复杂性，而我们的大脑已经进化到可以轻松处理。我们计划通过使用一种相对较新的技术——功能性磁共振成像（fMRI）来确定大脑中执行这些计算的部分。这是一种非侵入性技术，需要一个人躺在核磁共振扫描仪中，在扫描仪拍摄大脑图像的同时执行简单的眼球运动任务。有了这项技术，我们就能确定在执行每项任务时大脑的哪个区域最活跃，从而让我们了解大脑是如何工作的。大脑中有一个叫做顶叶的区域被认为与物体的定位有关，比如伸手去拿一杯茶。我们将使用功能磁共振成像来研究这一区域，以确定空间图是如何在顶叶中表示的。大脑的这个区域与另一个区域海马体交流，海马体被认为与导航有关，比如在房子里走动或在城市里开车。功能性核磁共振成像将用于研究受试者在电脑屏幕上模拟的迷宫中执行简单导航任务时的海马体。这将揭示海马体在导航中的作用以及顶叶与海马体的关系。我们希望从这项研究中对海马体有更深入的了解，这将使我们能够设计出一种强有力的方法，用fMRI对海马体功能进行成像。我们期望这些技术将有助于颞叶癫痫患者海马异常的诊断。

To accurately reach for an object or walk from one room to another, our brains need to be able to locate objects around us and detect obstacles in our path. Our amazing ability to make an accurate eye movement directly towards an object such as a cup of tea and move our hand smoothly and directly to the cup is something we all take for granted. However, this ability requires enormous computational complexity which our brains have evolved to handle with ease. We plan to determine the parts of the brain that perform these computations by using a relatively new technique called functional magnetic resonance imaging or fMRI. This is a non-invasive technique that requires a person to lie in an MRI scanner and perform simple eye movement tasks while the scanner takes images of the brain. With this technology we are able to determine which regions of the brain are most active during the performance of each task, thereby giving us an insight into how the brain works. An area of the brain called the parietal lobe is thought to be involved in the localization of objects, such as reaching for a cup of tea. We will study this area using fMRI to determine how a map of space is represented within the parietal lobe. This region of the brain communicates with another region, the hippocampus which is thought to be involved in navigation, such as walking about the house or driving in the city. Functional MRI will be used to study the hippocampus of our subjects while they perform simple navigational tasks through a maze which is simulated on a computer screen. This will reveal the role hippocampus plays in navigation and the relationship between the parietal lobe and hippocampus. We hope that the greater understanding of hippocampus that will arise from this study will enable us to devise a robust method for imaging hippocampal function with fMRI. We expect that these techniques will aid in the diagnosis of hippocampal abnormalities in patients with temporal lobe epilepsy.