Schei Jennifer L, McCluskey Matthew D, Foust Amanda J, Yao Xin-Cheng, Rector David M
Department of Physics and Astronomy, Washington State University, Pullman, WA 99164-2814, USA.
Neuroimage. 2008 Apr 15;40(3):1034-43. doi: 10.1016/j.neuroimage.2007.12.055. Epub 2008 Jan 11.
To identify the neural constituents responsible for generating polarized light changes, we created spatially resolved movies of propagating action potentials from stimulated lobster leg nerves using both reflection and transmission imaging modalities. Changes in light polarization are associated with membrane depolarization and provide sub-millisecond temporal resolution. Typically, signals are detected using light transmitted through tissue; however, because we eventually would like to apply polarization techniques in-vivo, reflected light is required. In transmission mode, the optical signal was largest throughout the center of the nerve, suggesting that most of the optical signal arose from the inner nerve bundle. In reflection mode, polarization changes were largest near the edges, suggesting that most of the optical signal arose from the outer sheath. In support of these observations, an optical model of the tissue showed that the outer sheath is more reflective while the inner nerve bundle is more transmissive. In order to apply these techniques in-vivo, we must consider that brain tissue does not have a regular orientation of processes as in the lobster nerve. We tested the effect of randomizing cell orientation by tying the nerve in an overhand knot prior to imaging, producing polarization changes that can be imaged even without regular cell orientations.
为了识别产生偏振光变化的神经成分，我们使用反射和透射成像方式，创建了受刺激的龙虾腿神经中传播动作电位的空间分辨电影。光偏振的变化与膜去极化相关，并提供亚毫秒级的时间分辨率。通常，信号是通过透过组织的光来检测的；然而，由于我们最终希望在体内应用偏振技术，所以需要反射光。在透射模式下，神经中心的光信号最强，这表明大部分光信号来自内部神经束。在反射模式下，边缘附近的偏振变化最大，这表明大部分光信号来自外部鞘膜。为支持这些观察结果，组织的光学模型表明，外部鞘膜更具反射性，而内部神经束更具透射性。为了在体内应用这些技术，我们必须考虑到脑组织不像龙虾神经那样具有规则的细胞排列方向。我们通过在成像前将神经打成反手结来测试随机化细胞方向的效果，即使没有规则的细胞方向，也能产生可成像的偏振变化。
