BRAIN EAGER: Genetic Access of Neuronal Populations Activated by Two Experiences in the Same Animal

哺乳动物的大脑由数亿到数十亿的神经细胞（神经元）组成，它们形成复杂的网络。感知、认知和行动如何通过神经元的活动反映出来，是现代神经科学的核心问题。研究人员之前已经开发出一种遗传方法来标记由特定感觉体验或行为事件激活的神经元，因此他们可以可视化它们的连接并测量它们的活动。在这项研究中，研究人员将开发新的方法来提高信噪比，以更有效地识别活跃的神经元，并在同一动物中标记两个不同的经验，以便他们可以直接比较两个神经元群体的生理特性，例如学习前后的生理特性。这些方法的成功将使科学家能够比较不同刺激和行为的大脑表征，以及学习后发生的变化。用于标记活跃神经元的方法（TRAP，用于活跃群体中的靶向重组）利用了立即早期基因的特性，其转录被神经元活动激活。这是通过使用小鼠遗传学将药物诱导型Cre重组酶置于立即早期基因启动子的控制下来实现的，使得药物活性期的经验永久地开启Cre报告转基因。这项研究将利用病毒转导和小鼠遗传学的组合来区别标记由两种不同经历激活的神经元。此外，使用光来局部沉默抑制性神经元的策略将用于在药物活性期期间在窄得多的时间窗内增强兴奋抑制比，从而增强TRAP效率。新的转基因小鼠和病毒载体将在验证后存放在公共储存库。

The mammalian brain consists of hundreds of millions to billions of nerve cells (neurons) that form complex networks. How perception, cognition, and action are reflected by the activities of neurons is a central question in modern neuroscience. The investigators have previously developed a genetic method to mark neurons that are activated by a specific sensory experience or behavioral episode, so they can visualize their connections and measure their activities. In this research, the investigators will develop new methods to improve the signal-to-noise ratio to more effectively identify the active neurons, and to mark two separate experiences differentially in the same animal so they can directly compare physiological properties of two populations of neurons, such as those before and after learning. The success of these approaches will enable scientists to compare brain representations of different stimuli and behavior, and what changes occur after learning.The method used to mark active neurons (TRAP, for targeted recombination in active populations) utilizes the property of immediate early genes, whose transcription is activated by neuronal activity. This was achieved using mouse genetics to place a drug-inducible Cre recombinase under the control of immediate early gene promoters, such that experience in the drug-active period turns on Cre reporter transgenes permanently. This research will utilize a combination of viral transduction and mouse genetics to differentially label neurons that are activated by two separate experiences. In addition, a strategy of using light to locally silence inhibitory neurons will be used to enhance excitation-to-inhibition ratio, and thereby enhance TRAP efficiency, in a much narrower time window during the drug-active period. The new transgenic mice and viral vectors will be deposited in public repositories after validation.