Interactions of the parietal cortex during cognition and sleep

下次当你发现自己盯着出租车司机的后脑勺时，请记住，除了学习和记住所有这些路线之外，他还需要处理所有从挡风玻璃上冲过的视觉信息，遵循你在后座上发出的命令，遵守道路交通规则，控制他在加速器和刹车上的尖锐的脚戳，并兴奋地谈论足球比赛的结果。所有这些都需要大量的大脑，同时活跃的专门大脑结构处理视觉，听觉，规则学习，决策，运动，语言和情感必须以某种方式协调它们的活动和相互作用。解码这些神经元网络在复杂行为中如何在多个大脑区域之间协调，这是一个相当大的挑战，需要最新的技术。但是，迎接这一挑战是至关重要的：这种协调的崩溃会导致精神分裂症和抑郁症等毁灭性疾病。我们应对这一挑战的方法非常直接：我们使用极细的电极束来记录大鼠和小鼠大脑中数百个脑细胞（“神经元”）产生的电活动，因为它们在迷宫中寻找巧克力，就像微型出租车司机一样。使用的电极大约是人类头发平均宽度的十分之一，可以同时监测多达128个电极，每秒32，000次。由于这些电极可以同时记录多个大脑结构中的多个神经元，这项技术使我们能够监测数百个神经元的活动，从而监测它们之间的相互作用。啮齿类动物和出租车司机大脑活动的一个显著特征是其节律性：神经元用于相互交流的电信号以不同的频率范围变化，有点像收音机的不同波长。我们最近已经证明，当某些大脑结构需要共享信息时（例如，“我刚刚去过哪里，下一个路口的规则是什么？”），它们通过在特定的频带上调整它们的活动来“调谐”彼此。然而，我们只展示了两个大脑结构的这一点-而且需要两个以上的大脑结构来做出决定并相应地指导你的行为。该项目旨在将这项工作扩展到称为“顶叶皮层”的第三种大脑结构。顶叶皮层受损的人在周围环境中的导航能力受损，并且往往注意力持续时间短，记忆力不可靠。来自猴子顶叶皮层的记录发现，它的神经元似乎编码了类似计划的复杂信号;例如，每当猴子计划将手臂伸向左边时，一个给定的神经元就会被激发。很明显，顶叶皮层正在处理一些有用的信息，但它如何与大脑的其他部分分享这些信息呢？使用我们在大鼠身上的多点记录，我们将看到当大鼠试图弄清楚他们的下一个巧克力来自哪里时，顶叶活动如何与大脑其他地方的活动“协调”。我们还将观察这种“调谐”是否在睡眠期间继续，当它可能与增强清醒时获得的记忆有关时（例如，最近在德国的一项研究表明，在睡眠期间对志愿者大脑的有节奏刺激改善了他们对以前学习过的事实的记忆）。理解顶叶皮层的相互作用和功能将为我们的大脑这个极其复杂的拼图游戏添加另一个重要的组成部分。现代技术和分析使这个难题变得可以解决;因此，像这样的项目对于我们理解正常的大脑功能以及理解大脑在复杂的精神疾病（如精神分裂症）中如何出错至关重要。

Next time you find yourself staring at the back of a taxi driver's head, remember that as well as learning and remembering all those routes, he needs to be processing all the visual information rushing through the windscreen, following the commands you bark from the rear seat, obeying road traffic regulations, controlling the sharp jabs of his feet on accelerator and brake, and chatting excitedly about the football results. All that takes a lot of brain, and the simultaneously active specialised brain structures that deal with vision, hearing, rule learning, decision-making, movement, language and emotion must somehow coordinate their activities and interactions with one another. Decoding how these networks of neurons are coordinated across multiple brain regions during complex behaviour presents a considerable challenge requiring the latest technology. But rising to meet this challenge is essential: breakdowns of this coordination give rise to devastating diseases like schizophrenia and depression. Our approach to addressing this challenge is quite direct: we use bundles of extremely fine electrodes to record the electrical activity produced by hundreds of brain cells ('neurons') in the brains of rats and mice as they navigate their way around mazes in search of chocolate, like miniature taxi drivers. The electrodes used are approximately one tenth as wide as the average human hair, and up to 128 of them can be monitored simultaneously, 32,000 times per second. Since these electrodes can record simultaneously from multiple neurons in multiple brain structures, this technology allows us to monitor the activity of hundreds of neurons, and hence their interactions underlying behaviour. A striking feature of brain activity in rodents and taxi drivers alike is its rhythmicity: the electrical signals that neurons use to communicate with one another wax and wane at a range of different frequencies, a bit like the different wavelengths on your radio. We have recently shown that when certain brain structures need to share information (for example, 'Where have I just been and what are the rules at the next junction?'), they 'tune in' to one another by aligning their activities at a specific frequency band. However, we have only shown this for two brain structures - and it takes more than two brain structures to make a decision and guide your behaviour accordingly. This project aims to extend this work into a third brain structure called the 'parietal cortex'. People with damage to their parietal cortex are impaired at navigating around their environment, and tend to have short attention spans and unreliable memory. Records from the parietal cortex of monkeys have found that its neurons seem to encode complex signals like plans; a given neuron fires, for example, every time the monkey plans to reach its arm to the left. Clearly the parietal cortex is dealing with some useful information, but how does it share this information with the rest of the brain? Using our multi-site recordings in rats, we are going to see how parietal activity 'tunes in' with activity elsewhere in the brain as rats try to figure out where their next chocolate treat is coming from. We are also going to see if this 'tuning in' carries on during sleep, when it might relate to strengthening memories acquired during wakefulness (e.g. a recent study in Germany showed that rhythmical stimulation of volunteers' brains during sleep improved their memories of previously learned facts). Understanding the parietal cortex's interactions and functions will add another essential piece to the enormously complex jigsaw puzzle that is our brains. Modern technology and analysis is making this puzzle solvable; projects like this are therefore essential to both our understanding of normal brain function, and to understanding how brains go wrong during complex psychiatric diseases like schizophrenia.