Modular High-Density Optoelectrodes for Local Circuit Analysis

重要性：一些科学问题，特别是在局部电路分析中，需要通过扰动受控数量和同时记录的神经元，以高的空间和时间分辨率独立地在多个部位操纵体内神经元。光遗传刺激是细胞类型特异性的，已被证明是最强大的电路控制手段。几个实验室已经开发出解决方案，将光学刺激传递到大脑深部结构，同时记录神经元。然而，通过放置在大脑表面上的光源或放置在距记录部位几百“μ“m的脑实质中的大纤维的刺激不可避免地激活许多未监测的神经元，使得直接和群体介导的效应的分离是不可能的。此外，用于激活深层神经元的高强度可能产生多个尖峰波形的叠加和相当大的光伪影。对于提供足够的工具以使局部回路刺激能够达到单个神经元的水平和具有兴奋/抑制模式的闭环相互作用，存在未满足的需求。本申请的目的是开发用于实现高度特异性神经回路控制的高密度光电极探针。基于我们以前在波导、耦合技术和高密度神经探针方面的经验，我们将实现一个无光纤、多通道、多波长的平台，用于同时进行低噪声电记录和光刺激。多种配置的验证将根据明确定义的基准在啮齿动物体内进行。 初步数据：我们已经证明了将光波导与密歇根神经探针单片集成的可行性，将光从对准的光纤传递到刺激部位。我们还实现了聚合物（SU-8）和氮氧化物波导在各种配置的光混频器和分路器，以引导光光刻定义的模式。我们将制造的探针植入大鼠体内，并成功记录了海马CA 1区对光刺激（λ = 473 nm）的神经尖峰反应。 具体目标：在目标1中，我们将开发一个有效的耦合方案，从光源通过新颖的反射器设计和高约束波导实现。我们将通过参数化和自由形式的光学建模来优化波导和反射器的效率。在目标2中，我们将制作和组装多通道多位点光电极阵列，以实现60 μ W的输出从低轮廓波导的同时，低噪声记录和光刺激。这些任务包括微加工、热优化、片上驱动器、低噪声优化、装配改进和验证测试。在目标3中，将通过两个体内实验来验证所制造的探针：一个是以极低功率（3-10 μ W）激活少数或单个神经元，另一个是使用多色对照与鉴定的神经元类型的闭环光遗传学相互作用。

Significance: A number of scientific questions, especially in local circuit analysis, require manipulating neurons in vivo at multiple sites independently at high spatial and temporal resolutions by perturbing a controlled number and simultaneously recorded neurons. Optogenetic stimulation is cell-type specific which has proven to be the most powerful means of circuit control. Several laboratories have developed solutions to deliver optical stimulation to deep brain structures whilst simultaneously recording neurons. However, stimulation through light sources placed on the surface of the brain or large fibers placed in the brain parenchyma a few hundred “mu”m from the recording sites inevitably activate many un-monitored neurons, making the separation of direct and population-mediated effects impossible. Moreover, the high intensity used for the activation of deep neurons may generate superposition of multiple spike waveforms and considerable light artifacts. There is an unmeet need to provide an adequate tool to enable local circuit stimulation to the level of single neurons and closed-loop interactions with excitation/inhibition patterns. The objective of this application is to develop high-density optoelectrode probes for enabling highly specific neural circuit control. Based upon our previous experience with waveguides, coupling technology, and high-density neural probes, we will implement a fiber-less, multi-channel, multi-wavelength platform for simultaneous, low-noise electrical recording and optical stimulation. Validation of multiple configurations will occur in vivo in rodents against clearly defined benchmarks. Preliminary Data: We have demonstrated the feasibility of the monolithic integration of optical waveguides with Michigan neural probes, delivering light from an aligned optical fiber to the stimulation site. We have also implemented both polymer (SU-8) and oxynitride waveguides in various configurations as optical mixers and splitters to guide light in lithographically-defined patterns. We implanted the fabricated probe in a rat and have successfully recorded neural spiking responses to optical stimulation (lambda=473nm) from the hippocampus CA1 region. Specific Aims: In aim 1, we will develop an efficient coupling scheme from the light source through novel reflector design and high-confinement waveguide implementation. We will optimize the waveguide and reflector efficiency through parametric and free-form optical modeling. In aim 2, we will fabricate and assemble the multi-channel multi-site optoelectrode array to achieve 60-“mu”W output from the low-profile waveguide for simultaneous, low-noise recording and optical stimulation. The tasks include microfabrication, thermal optimization, on-chip driver, low-noise optimization, assembly refinement and verification testing. In aim 3, the fabricated probes will be validated by two in-vivo experiments: one is activating few or single neurons at extremely low power (3-10”mu”W) and the other is closed-loop optogenetic interaction with identified neuron types using multi-color control.