CAREER: Astrocytic Integration of Cortical Wake Signals

睡眠在动物王国中被广泛观察到，这一事实证明了睡眠的基本生物学重要性，睡眠剥夺可能对生理和认知都有害。同样，清醒的重要性是不言自明的：动物的繁殖、觅食和躲避捕食都依赖于清醒。然而，直到最近，人们对调节清醒和睡眠的神经回路仍然知之甚少。一项调查暗示了一种非神经元细胞类型参与了睡眠-觉醒控制。这种细胞——星形胶质细胞——构成了大脑中最大的一类非神经元细胞，它已被证明能影响周围神经元的活动。然而，星形胶质细胞参与睡眠和清醒的方式在很大程度上尚未被探索。该项目测试星形胶质细胞是否感知觉醒特异性信号，并通过改变大脑状态对这些信号做出反应。为了进行这些实验，使用了先进的成像工具来观察大脑中不同形式的细胞活动。该项目的更广泛影响是使跨学科研究在受训者的职业生涯早期变得容易和常规。这样做的动机在于，具有物理科学经验的学员更有可能自己成为工具构建者，而实时观察科学的发展可以激发并授权学员深入思考他们周围的生物学。神经调节信号对动物行为至关重要，部分是通过大脑在不同状态之间的转换，而最引人注目的大脑状态转换可以说是发生在清醒和睡眠之间的那些状态。然而，皮层下核产生的神经调节输入如何在皮层水平上整合以调节群体水平的状态转移仍不清楚。一些神经调节受体在皮层神经元和星形胶质细胞上均有表达，这提高了星形胶质细胞与神经元在感知神经调节信号以启动和/或维持皮层清醒方面的合作伙伴的可能性。星形胶质细胞是协调大规模神经元回路变化的一个有吸引力的目标，它们也通过细胞外平衡和形态的脑状态依赖性变化与睡眠/觉醒有关。这个项目的首要假设是，星形胶质细胞的神经调节信号，以及随后星形胶质细胞对群体神经元活动的影响，对于在哺乳动物大脑的最大区域皮层中整合清醒状态信号至关重要。本研究利用先进的双光子成像技术、现代神经生物学工具来调节神经活动，以及星形胶质细胞特异性技术来探测星形胶质细胞对神经调节信号的细胞生物学反应，并绘制清醒和睡眠期间的星形胶质细胞动力学图，为测试星形胶质细胞激活对清醒状态和皮层回路中神经信号的影响做准备。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The fundamental biological importance of sleep is demonstrated by the fact that sleep is observed widely across the animal kingdom, and that sleep deprivation can be harmful both physiologically and cognitively. Likewise, the importance of wake is axiomatic: reproduction, feeding, and escape from predation depend on an animal being awake. However, until recently, the neural circuits that regulate wake and sleep have remained poorly understood. One strand of inquiry has implicated a non-neuronal cell type in sleep-wake control. This cell—the astrocyte—makes up the largest class of non-neuronal cells in the brain, and it has been shown to affect the activity of surrounding neurons. However, the ways in which astrocytes are involved in sleep and wake are largely unexplored. This project tests whether astrocytes sense wake-specific signals and respond to these signals by changing the state of the brain. To perform these experiments, advanced imaging tools to watch different forms of cellular activity in the brain are used. The broader impacts of this project aim to make interdisciplinary research accessible and routine to trainees early in their careers. The motivation for this lies in the fact that trainees with experience in physical sciences are more likely to become tool builders themselves, and that watching science happening in real time can excite and empower trainees to think deeply about the biology around them.Neuromodulatory signaling is critical for animal behavior, in part by shifting the brain among various states, and the most dramatic brain state shifts are arguably those that occur between wake and sleep. However, how neuromodulatory inputs arising in subcortical nuclei are integrated at the level of the cortex to regulate population-level state shifts remains unclear. Several neuromodulatory receptors are expressed on both cortical neurons and astrocytes, raising the possibility that astrocytes are partners with neurons in sensing neuromodulatory cues to initiate and/or maintain wake in the cortex. Astrocytes are an attractive target for coordinating large-scale neuronal circuit changes, and they have also been implicated in sleep/wake via brain state-dependent changes in extracellular balance and morphology. The overarching hypothesis for this project is that neuromodulatory signaling to astrocytes, and subsequent astrocytic effects on population neuronal activity, is critical for integrating wake-state signals in the cortex, the largest area of the mammalian brain. The research addresses these questions using advanced two-photon imaging, modern neurobiological tools to modulate neural activity, and astrocyte-specific technology to probe the cell biological responses of astrocytes to neuromodulatory cues, and map astrocytic dynamics across wake and sleep, in preparation to test the effects of astrocyte activation on wake state and neural signaling in a cortical circuit.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.