Modular nanophotonic probes for dense neural recording at single-cell resolution

描述(由申请人提供)：在过去的几十年里，我们对单个神经元的属性及其在脑计算中的作用的理解有了很大的进步。然而，我们仍远未了解大型细胞组合如何相互作用来处理信息。电生理学是具有无与伦比的时间分辨率的金标准，但就其能力记录而言，目前仅限于具有细胞类型特异性的单个神经元的体积。光学成像提供了一种强大的替代方法，它能够通过遗传编码的荧光标记在解剖空间定位神经元和细胞类型特异性。目前最先进的脑功能成像技术是双光子荧光激光扫描显微镜。但这种方法只在大脑表面或透明组织上效果最好，而且不易扩展。更广泛地说，组织中的光散射和吸收施加了显著的基本限制：在哺乳动物的大脑中，体内可到达的深度仅限于皮质浅层区域，d1 mm。由于探头直径较大(0.3-1毫米)，为避开这些限制而开发的内窥镜方法会对成像部位上方的组织造成重大损害，因此非常有限(例如，不能用于研究皮质柱)。在这里，我们提出了一种新的功能光学成像范式，它克服了这些限制。它允许在高度分散的脑组织中进行具有细胞分辨率的功能成像，能够完全覆盖目标体积内的所有神经元，并具有长期的人类应用前景。我们的方法，我们称之为集成神经光子学，是基于在大脑内部分布密集的发射器和探测器像素的3-D点阵。这些像素阵列被嵌入到神经光子探测器上，实现为可植入的超窄小腿，利用了集成纳米光子学的最新进展。与功能光学记录器(如GCaMP6)配合使用，一个25杆探头模块将能够以单个细胞分辨率记录1-mm3体积内(约100,000个神经元)的所有神经元的活动。该方法是可扩展的；可以对多个模块进行平铺，以密集覆盖大脑深处的扩展区域。它最终将允许同时记录大脑中任意位置和深度的数百万个神经元，以揭示具有单细胞分辨率和细胞类型特异性的完整神经网络的动力学。超窄的神经光子探头将对脑组织产生最小的扰动，造成微不足道的组织位移和微小的局部能量消耗。重要的是，通过现有的基于晶片规模的铸造(工厂)方法，它们很容易生产，因此将被社区广泛使用。它们将改变脑计算和神经精神障碍的电路水平机制的研究，并将通过体内高通量筛选来加速药物发现。我们的多学科团队涵盖了所有必要的专业知识：纳米技术和大规模集成，以开发神经光子探测器阵列(Roukes，Shepard)，以及体内测试和计算分析(Tolias，Siapas)。

DESCRIPTION (provided by applicant): Our understanding of the properties of individual neurons and their role in brain computations has advanced significantly during the last few decades. However, we are still very far from understanding how large assemblies of cells interact to process information. Electrophysiology is the gold standard with unmatched temporal resolution, but is currently limited in terms of its ability record from every single neuron withina volume with cell-type specificity. Optical imaging provides a powerful alternative method, which enables localization of neurons in anatomical space and cell-type specificity via genetically encoded fluorescent markers. The current state-of-the-art in functional brain imaging is two-photon fluorescence laser-scanning microscopy. But this approach works best only on the surface of the brain, or transparent tissues and is not easily scalable. More generally, light scattering and absorption in tissue impose significant fundamental limits: in mammalian brains, accessible depths in vivo are restricted to superficial cortical regions, d1mm. Endoscopic methods developed to circumvent such restrictions impart significant damage to tissue above the imaging site given the large probe diameter (0.3 to >1 mm) and thus are quite limited (e.g. cannot be used to study cortical columns). Here we propose a novel paradigm for functional optical imaging that surmounts these limitations. It permits function- al imaging with cellular resolution in highly scattering brain tissue, enables complete coverage of all neurons within a target volume, and has long-term prospects for human applications. Our approach, which we term integrated neurophotonics, is based on distributing a dense 3-D lattice of emitter and detector pixels within the brain itself. These pixel arrays are embedded onto neurophotonic probes, realized as implantable, ultra narrow shanks that leverage recent advances in both integrated nanophotonics. Used with functional optical reporters (e.g. GCaMP6), one 25-shank probe module will be capable of recording the activity of all neurons within a 1- mm3 volume (~100,000 neurons) with single cell resolution. The methodology is scalable; multiple modules can be tiled to densely cover extended regions deep within the brain. It will ultimately permit simultaneous recording from millions of neurons at arbitrary positions and depths in the brain, to unveil the dynamics of complete neural networks - with single-cell resolution and cell-type specificity. Ultra-narrow neurophotonic probes will perturb brain tissue minimally, imposing negligible tissue displacement and minute local power dissipation. Importantly, they are readily producible though existing wafer-scale foundry (factory) based methods and thus will be widely available for use by the community. They will transform studies of circuit- level mechanisms of brain computation and neuropsychiatric disorders, and will accelerate drug discovery via high throughput in vivo screening. Our multi-disciplinary team spans all requisite expertise: nanotechnology and large-scale-integration for development of neurophotonic probe arrays (Roukes, Shepard), and in vivo testing and computational analysis (Tolias, Siapas).