Ultra High-density Optomechanic Neural Interfaces

项目摘要 对神经回路的多尺度，机械理解，包括局部和全脑 相互联系仍然难以捉摸。一个根本的挑战是缺乏监测工具， 高时空分辨率，局部神经元集合的活动同时在不同区域的 清醒、行为自由的动物的大脑。这就需要设计出一种高密度的神经探针， 记录来自数千个神经元的高时空分辨率的信息。虽然有巨大的 传统的被动和主动电子神经探针的设计进展，这些技术是 达到缩放极限。我们需要打破传统的记录和中继电 使用被动或主动电子神经探针的神经信号， 我们可以从大脑中记录的同步通道的数量。在这里，我们提出了一种破坏性的方法， 基于光学和微机电系统（MEMS）的基本进步， 创新光机探头，可能同时具有超过几千个 有源记录电极与传统无源探头的覆盖区相同。所有记录的神经元 在我们的设计中，信号在光学域中被编码，以利用光的带宽， 在单个光波导上将所记录的聚集神经信号传送到大脑外部。在这 在一种方案中，每个记录通道被编码到沿着相同通道沿着行进的光的单个波长上 波导管这种波长域多路复用（WDM）方法使得能够真正地同时记录多个光信号。 通道，与有源电子神经探针中使用的时域复用（TDM）方案不同， 其依赖于多个通道的顺序记录。因此，我们的设计能够大规模地扩展 同时记录的通道数，同时增强SNR，保留带宽，并最小化 主动电子神经探针的不利影响，如大脑内部的发热。的核心单元格 我们的神经探针是一种机电传感器，它可以检测神经电信号，并将其转换为小信号。 膜的机械运动，其又调制光子微谐振器。因此，电 神经信号被转换为机械信号，然后转换为光学信号。超高品质因数光学 微谐振器增强了检测信号。耦合到多个微谐振器的单个公共波导 将光信号传送到大脑外部的后端。这种新颖的设计使大规模的 记录通道的数量，而不增加神经探针的尺寸。此外，转换 将电信号转换为光信号导致增强的信噪比（SNR）， 发射信号不受不必要的电干扰。在成功演示多路复用后， 电光机械神经记录在这个项目中，结果可以在未来的努力中扩展到i）开发 甚至具有超过1000个通道的更高密度的神经探针，和ii）证明其在体内的应用。

Project Summary A multi-scale, mechanistic understanding of neural circuits that includes both local- and whole-brain interconnections still remains elusive. One of the fundamental challenges is the lack of tools for monitoring, with high spatiotemporal resolution, the activity of local neuron ensembles simultaneously in different regions of the brain in awake, freely-behaving animals. This calls for the design of ultrahigh density neural probes capable of recording from thousands of neurons with high spatiotemporal resolution. While there has been tremendous progress on the design of conventional passive and active electronic neural probes, these technologies are reaching scaling limits. We need to break away from the conventional scheme of recording and relaying electrical neural signals using passive or active electronic neural probes to enable breakthrough improvements in the number of simultaneous channels that we can record from the brain. Here, we propose a disruptive approach based on fundamental advancements in optics and microelectromechanical systems (MEMS) to deliver an innovative opto-mechanical probe that can potentially have more than a couple of thousand simultaneously active recording electrodes in the same footprint of a conventional passive probe. All of the recorded neural signals in our design are encoded in the optics domain to leverage the ultrahigh bandwidth of light for communicating the recorded aggregate neural signals to outside the brain on a single optical waveguide. In this scheme, each recording channel is encoded onto a single wavelength of light that travels along the same waveguide. This wavelength domain multiplexing (WDM) method enables a true simultaneous recording of many channels, unlike the time domain multiplexing (TDM) scheme that is used in active electronic neural probes, which relies on sequential recording of multiple channels. Therefore, our design enables massive scaling of the number of simultaneously recorded channels, while enhancing SNR, preserving the bandwidth, and minimizing adverse effects of active electronic neural probes such as heat generation inside the brain. The core unit cell of our neural probe is an electromechanical sensor that detects electrical neural signals and converts them to small mechanical motions of a membrane, which in turn modulates a photonic microresonator. Therefore, the electrical neural signal is transformed to a mechanical and then an optical signal. The ultra-high quality factor optical microresonator enhances the detected signals. A single common waveguide coupled to multiple microresonators carries the optical signals to the backend outside the brain. This novel design enables massive scaling of the number of recording channels without increasing the size of the neural probe. Moreover, the conversion of electrical signals to optical signals results in enhanced signal-to-noise ratio (SNR) and also makes the transmitted signals immune to unwanted electrical interference. After successful demonstration of multiplexed electro-opto-mechanic neural recording in this project, the results can be extended in future efforts to i) develop even much higher density neural probes with more than 1000 channels and ii) demonstrate its in vivo application.