Carter Kathleen M, George John S, Rector David M
VCAPP Department, Washington State University, P.O. Box 646520, Pullman, WA 99164, USA.
J Neurosci Methods. 2004 May 30;135(1-2):9-16. doi: 10.1016/j.jneumeth.2003.11.010.
Simultaneous fast birefringence and scattered light changes associated with crustacean nerve activation have different time courses and are produced by separate biophysical mechanisms. Technological advances in illumination, photodiodes and amplification circuitry achieved better signal-to-noise than earlier studies revealing optical signals in axonal nerve bundles as small as crayfish ventral cord and claw. The birefringence measurements yielded signals that could be observed in single trials, with temporally separated peaks associated with axonal populations of different diameters. A slit aperture placed perpendicular to the nerve reduced the spatial-temporal integration and enhanced the temporal structure of the separate peaks in the birefringence signal. Moving the slit aperture farther from the stimulation point delayed the signal in time, and also enhanced the separation between peaks. Different propagation velocities of the separate peaks provided evidence for at least three neuronal populations in the bundle. These studies underscore the advantages of birefringence over scattering measurements. Application of birefringence methods can optimize non-invasive imaging techniques being developed to detect fast optical responses associated with electrical neural activity in humans.
与甲壳类动物神经激活相关的同时快速双折射和散射光变化具有不同的时间进程，且由不同的生物物理机制产生。照明、光电二极管和放大电路方面的技术进步比早期研究实现了更好的信噪比，早期研究揭示了轴突神经束中如小龙虾腹神经索和爪子那样小的光学信号。双折射测量产生的信号可以在单次试验中观察到，具有与不同直径轴突群体相关的时间上分离的峰值。垂直于神经放置的狭缝孔径减少了时空积分，并增强了双折射信号中单独峰值的时间结构。将狭缝孔径移离刺激点会使信号在时间上延迟，并且还增强了峰值之间的分离。单独峰值的不同传播速度为束中至少三个神经元群体提供了证据。这些研究强调了双折射相对于散射测量的优势。双折射方法的应用可以优化正在开发的非侵入性成像技术，以检测与人类神经电活动相关的快速光学反应。
