Measurement of the neural activation potential of rat cerebral cortex using functional optical reflection tomography

我们的研究目标是提出和演示一种新的功能光学反射层析成像（f-ORT）。这种独特的技术被用于测量大鼠大脑皮层神经激活电位的时空分布，表明f-ORT对脑神经学是有效的。(1)利用SLD作为现有光学相干层析成像（OCT）的光源；但是，SLD的相干长度为10 ~ 20 μm，不足以检测神经激活电位。为了检测，SLD被锁模钛蓝宝石激光器取代，该激光器提供的脉冲宽度短至lOfs。对干涉仪色散进行适当补偿后，该激光器可提供3 μm空间分辨率的OCT。(2)为了实现上述高分辨率OCX，我们开发了1,3 μm OCT，将成像深度提高到1.5mm以上。随后，将相干门光学与共聚焦光学相结合，得到了期望的光学反射层析成像。(3)为了检测与心率同步的神经激活电位，必须尽可能快地获取成像数据。这种高速数据采集可以通过非机械光延迟扫描来实现。在f-ORT中，光延迟扫描是由PZT光纤相位调制器完成的，因此每秒可以获得50次以上的光延迟扫描。对所有光栅扫描信号进行汇总，大大提高了信噪比。(4)在初步实验中，对大鼠施加声音刺激时，f-ORT检测到折射率的变化。这种指数变化可能与声音刺激引起的神经激活电位相对应。声刺激后，在100 μm深的区域内检测到光反射信号的显著变化。在上述研究成果的基础上，我们一直在开发用于脑神经学的f-ORT。少

Our research target is proposal and demonstration of a novel functional optical reflection tomography (f-ORT). This unique technique is used for measurement of spatial and temporal distribution of neural activation potential of the cerebral cortex of rats, showing that the f-ORT is effective for brain neurology.(1) A SLD is used as the light source of the existing optical coherence tomography (OCT); however, the coherence length of SLD is 10 to 20 μm which is insufficient for detection of neural activation potential. In order for the detection, the SLD was replaced by a mode-locked Ti:sapphire laser which supplied the pulsewidth as short as lOfs. This laser can provide us OCT with the spatial resolution of 3 μm after proper compensation of chromatic dispersion of the interferometer.(2) In order to the high-resolution OCX described above, we developed the 1,3-μm OCT in which the imaging depth is improved to be 1.5mm or more. Subsequently, the desired optical reflection tomography was de … More veloped by combination of the coherence-gate optics and confocal optics.(3) The imaging data must be acquired as fast as possible in order to detect the neural activation potential in synchronization with the cardiac rate. Such a high-speed data acquisition can be realized by non-mechanical optical-delay scanning. In the f-ORT, the optical-delay scanning is performed by PZT fiber phase modulators, as a result, more than 50 optical-delay scans per second were obtained. All the raster scan signals are summed up to improve drastically the signal-to-noise ratio.(4) In the preliminary experiment, a refractive index change was detected by the f-ORT when a sound stimulus was applied to a rat. The index change may correspond to the neural activation potential due to a sound stimulus. A remarkable change of the optical reflection signal was detected in a 100-μm deep area 20s after application of the sound stimulus. On the basis of research results, as mentioned above, we have been developing the f-ORT for brain neurology. Less