Department of Electrical Engineering, University of Colorado Denver, Colorado, United States of America.
PLoS One. 2013 Jul 9;8(7):e67626. doi: 10.1371/journal.pone.0067626. Print 2013.
Recently developed optogenetic tools provide powerful approaches to optically excite or inhibit neural activity. In a typical in-vivo experiment, light is delivered to deep nuclei via an implanted optical fiber. Light intensity attenuates with increasing distance from the fiber tip, determining the volume of tissue in which optogenetic proteins can successfully be activated. However, whether and how this volume of effective light intensity varies as a function of brain region or wavelength has not been systematically studied. The goal of this study was to measure and compare how light scatters in different areas of the mouse brain. We delivered different wavelengths of light via optical fibers to acute slices of mouse brainstem, midbrain and forebrain tissue. We measured light intensity as a function of distance from the fiber tip, and used the data to model the spread of light in specific regions of the mouse brain. We found substantial differences in effective attenuation coefficients among different brain areas, which lead to substantial differences in light intensity demands for optogenetic experiments. The use of light of different wavelengths additionally changes how light illuminates a given brain area. We created a brain atlas of effective attenuation coefficients of the adult mouse brain, and integrated our data into an application that can be used to estimate light scattering as well as required light intensity for optogenetic manipulation within a given volume of tissue.
最近开发的光遗传学工具提供了强大的方法来光学激发或抑制神经活动。在典型的体内实验中，光通过植入的光纤传递到深部核团。光强度随距离光纤尖端的增加而衰减，这决定了可以成功激活光遗传学蛋白的组织体积。然而，这种有效光强度的体积如何随脑区或波长而变化，尚未得到系统研究。本研究的目的是测量和比较光在小鼠大脑不同区域的散射情况。我们通过光纤向小鼠脑干、中脑和前脑组织的急性切片输送不同波长的光。我们测量了光强随光纤尖端距离的变化，并利用数据对特定区域的光在小鼠大脑中的传播进行建模。我们发现不同脑区的有效衰减系数存在显著差异，这导致光遗传学实验对光强度的要求存在显著差异。不同波长的光的使用还改变了光对给定脑区的照明方式。我们创建了成年小鼠大脑有效衰减系数的脑图谱，并将我们的数据整合到一个应用程序中，该应用程序可用于估计给定组织体积内光散射以及光遗传学操作所需的光强度。
