Modular High-Density Optoelectrodes for Local Circuit Analysis

意义：许多科学问题，特别是在局部电路分析中，需要通过干扰控制数量和同时记录的神经元，在高空间和时间分辨率下独立地操纵体内多个位置的神经元。光遗传刺激是细胞类型特异性的，已被证明是最有效的电路控制手段。几个实验室已经开发出解决方案，在记录神经元的同时向大脑深部结构提供光学刺激。然而，通过放置在大脑表面的光源或放置在距离记录位点几百“亩”米的脑实质中的大纤维进行刺激，不可避免地会激活许多未被监测的神经元，从而使直接效应和群体介导效应无法分离。此外，用于激活深层神经元的高强度可能会产生多个尖峰波形的叠加和相当大的光伪影。目前还不需要提供一种足够的工具，使局部回路刺激达到单个神经元的水平，并与兴奋/抑制模式进行闭环相互作用。该应用程序的目的是开发高密度光电极探针，以实现高度特定的神经回路控制。基于我们之前在波导、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的电记录和光刺激。多种配置的验证将在啮齿类动物体内根据明确定义的基准进行。

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.