Five-dimensional optoacoustic tomography for large-scale electrophysiology in scattering brains

 描述(由申请人提供)：神经科学对大规模神经记录技术有基本要求，以确保在了解大脑功能、诊断和治疗神经疾病方面取得快速进展。目前，在单个细胞上观察快速神经元活动的局部化光学显微镜研究之间存在很大差距。 分辨率水平以及宏观成像方式提供的缓慢血流动力学和脑代谢的全脑观察。这项拟议的两年计划旨在开发新的光声神经成像工具，以在毫秒范围内以前所未有的时间分辨率对大规模分布的神经元群体的活动进行体积测量。这一目标将通过建造一台层析光声扫描仪来实现，该扫描仪可以同时记录球面几何形状的三维光声数据。体积记录的高时间分辨率将使使用快速电压敏感指示器直接跟踪动作电位成为可能。由此产生的扫描仪将同时记录散布在大脑中的大范围视野中的活动，可能会到达小鼠的海马体和更远的地方。将进一步采用激发激光波长的快速调谐，以便能够同时获取五维(即实时体积多光谱)光声数据，这将提高探测活动报告的快速光谱变化的灵敏度。该行动计划包括使用神经细胞培养筛选几个潜在的电压成像候选对象，包括遗传指标。随后将在成年斑马鱼和小鼠的孤立散布脑中进行系统验证，旨在建立检测自发和刺激驱动活动模式引起的电压信号瞬变的灵敏度和时空分辨率指标。虽然像双光子成像这样的3D光学显微镜技术的主要重要性最近在大脑计划中得到了强调，但它们通常仅限于观察较小(~1mm3)的表面位置的体积，时间分辨率相对较低，进一步需要高度侵入性的可以改变活动的颅窗。相比之下，所提出的方法是为非侵入性的脑深部观察量身定做的，并且是以快速体积帧速率和接近细胞尺度的分辨率同时成像大视野的理想方法。此外，到目前为止，其他光声方法只关注血液动力学变化和血液氧合，这是大脑活动的缓慢和间接指标。这项拟议的研究将首次检验电压敏感指示器的快速光声信号，从而打破光学显微镜在散射大脑中长期存在的穿透障碍。

 DESCRIPTION (provided by applicant): Neuroscience has an essential requirement for large-scale neural recording technologies to ensure rapid progress in the understanding of brain function, diagnosis and treatment of neurological disorders. At present, a large gap exists between the localized optical microscopy studies looking at fast neuronal activities at single cell resolution level and the whole-brain observations of slow hemodynamics and brain metabolism provided by the macroscopic imaging modalities. The proposed two-year project is aimed at developing novel optoacoustic neuroimaging tool to volumetrically monitor activity of large distributed neuronal populations with unprecedented temporal resolution in the millisecond range. This goal will be accomplished by constructing a tomographic optoacoustic scanner to simultaneously record three- dimensional optoacoustic data in a spherical geometry. The high temporal resolution in volumetric recordings will make it possible to directly track action potentials using fast voltage-sensitive indicators. The resulting scanner will simultaneously record activity from large fields of view in scattering brains, potentially reaching the mouse hippocampus and beyond. Rapid tuning of the excitation laser wavelength will be further employed to enable simultaneous acquisition of five-dimensional (i.e. real-time volumetric multi- spectral) optoacoustic data, which will provide enhanced sensitivity in detecting rapid spectral variations of the activity reporters. The plan of action includes screening of several potential candidates for voltage imaging, including genetic indicators, using neuronal cell cultures. System validation will be subsequently performed in isolated scattering brains of adult zebrafish and mice, aiming at establishing sensitivity and spatiotemporal resolution metrics in detecting voltage signal transients due to spontaneous and stimulus- driven activity patterns. While the major importance of 3D optical microscopy techniques like two-photon imaging has been highlighted recently within the BRAIN initiative, they are generally limited to looking at small (~1mm3) superficially-located volumes with relatively slow temporal resolution, further requiring highly invasive cranial windows that can alter activity. In contrast, the proposed method is tailored for non-invasive deep brain observations and is ideal for simultaneous imaging of large fields of view at rapid volumetric frame rates and resolution approaching cellular scale. Furthermore, other optoacoustic approaches looked so far only at hemodynamic changes and blood oxygenation, slow and indirect indicators of brain activity. The proposed study will be the first to examine fast optoacoustic signatures of voltage-sensitive indicators, thus shattering the longstanding penetration barrier of optical microscopy in scattering brains.