Optical imaging of neural activity based on the Lorentz effect

项目摘要/摘要 直接评估神经活动的无标记成像技术的发展仍然是当务之急 需要。在旨在检测与动作电位相关的瞬时信号的各种技术中 (AP)传播，光学技术有可能揭示和定位具有高空间分辨率的AP。 时间分辨率。例如，差分相位干涉测量，然后是相敏测量 光谱域光学相干层析成像(OCT)的测量使我们能够检测AP- 无髓鞘无脊椎动物轴突的相关纳米级瞬时结构变化。为了获得 神经功能的有用测试，然而，对两者的对比增强方法的研究 需要有髓神经纤维和无髓神经纤维。该项目的长期目标是提供非 在基础科学研究中有用的神经功能的接触深度分辨光学测量。 该项目的总体目标是使用多对比度OCT和对比度增强方法 有髓和无髓神经模型中神经活动的深度分辨无标记成像。这个 这项工作背后的假设是，正确定向的外部静态磁场会产生洛伦兹力 在起作用的神经中(由于离子运动/动作电流)，从而导致机械性 伴随AP传播的波，有助于神经活动的光学成像。相敏 OCT可以很好地定位这种亚纳米灵敏度的瞬变信号。我们还将监测 强度(反射率)和双折射(延迟)信号作为神经活动的额外指示。至 为了达到这一应用的目标，我们将追求基于Lorentz的神经活动的光学成像 在体外制剂(特异性目标1)和体内视皮层(特异性目标2)中的作用。随着成功 在完成拟议的工作后，我们将取得以下成果。使用Lorentz的可行性 有助于AP的无标签光学成像的效果将被揭示。这也将通知相关的人 用于确定洛伦兹效应成像是否在当前能力范围内的成像场 技术如果我们的工作被证明是有用的，它将支持实验室中的功能神经研究 布景。这一结果也可能表明更具挑战性的体内应用需要掺入 主动跟踪系统，以实现所需的稳定性。

PROJECT SUMMARY / ABSTRACT The development of label-free imaging technologies that directly assess neural activity remains a pressing need. Among a variety of techniques that aim to detect transient signals associated with action potential (AP) propagation, optical techniques have the potential for revealing and locating APs with high spatio- temporal resolution. For instance, differential-phase interferometry and then phase-sensitive measurements of spectral-domain optical coherence tomography (OCT) have allowed us to detect AP- related nanometer-scale transient structural changes from unmyelinated invertebrate axons. To obtain useful tests of nerve function, however, investigations on contrast enhancement methods for both myelinated and unmyelinated nerve fibers are needed. The long term goal of this project is to provide non- contact depth-resolved optical measurements of nerve function that are useful in basic scientific research. The overall objective of this project is to use multi-contrast OCT and contrast enhancement methods for depth-resolved label-free imaging of neural activity in myelinated and unmyelinated nerve models. The hypothesis behind the work is that a properly directed external static magnetic field generates Lorentz force in functioning nerve (due to ionic movements / action currents), which consequently induces a mechanical wave accompanying AP propagation and facilitates the optical imaging of neural activity. Phase-sensitive OCT is well poised to locate such transient signals with sub-nanometer sensitivity. We will also monitor the intensity (reflectivity) and birefringence (retardance) signals as additional indications of neural activity. To achieve the objective of this application, we will pursue optical imaging of neural activity based on Lorentz effect in ex-vivo preparations (Specific Aim 1) and in-vivo visual cortex (Specific Aim 2). With successful completion of the proposed work, we will achieve the following outcomes. The feasibility of using Lorentz effect to aid label-free optical imaging of APs will be revealed. This will also inform people in related imaging fields to determine whether the Lorentz effect imaging is within the capabilities of current technology. If our work is shown to be useful, it will support functional neural investigations in laboratory setting. The results may also suggest more challenging in-vivo applications that require incorporation of active tracking systems for the needed stability.