Data 1 of 3 for: Optical coherence tomography imaging of evoked neural activity in sciatic nerve of rat

Objective: To investigate changes in intensity, phase retardation, phase, and frequency spectra obtained from optical coherence tomography (OCT) images in response to evoked neural activity in sciatic nerve of rat in vitro.
Approach: M-scans with 20 μs temporal resolution were obtained on peripheral nerves of rat using a swept source polarisation sensitive optical coherence tomography (PS-OCT) system, while a nerve cuff acquired electrical neural recordings. From a total of 10 subjects: 3 had no stimulation (controls), 3 had paw stimulation, and 4 had nerve stimulation. Changes in the OCT signal intensity, phase retardation, phase, and frequency spectra were calculated for each subject and compared to the control subjects as well as reference samples of a mirror and microspheres in solution.
Main results: Observed changes in phase retardation and phase were not above the noise level of reference mirror sample. Observed changes in intensity in 3 paw stimulation and 2 nerve stimulation subjects and changes in frequency spectra amplitude in 2 paw stimulation were above the reference noise level. The delayed onset and extended duration of the changes in intensity and frequency spectra amplitude were temporally consistent with osmotic swelling from potassium ion currents in myelinated fibres which has previously been characterised in squid and crab nerve using light scattering techniques but has not been reported using OCT on myelinated fibres.
Significance: Imaging osmotic swelling in neural tissue using OCT signal intensity and frequency spectra creates exciting new possibilities for functional imaging in peripheral nerves and white matter of the brain.

研究目的：探究离体大鼠坐骨神经受诱发神经活动刺激时，其光学相干断层扫描（optical coherence tomography, OCT）图像所获取的信号强度、相位延迟、相位及频谱的变化规律。
研究方法：采用扫频源偏振敏感光学相干断层扫描（swept source polarisation sensitive optical coherence tomography, PS-OCT）系统对大鼠外周神经进行扫描，获取时间分辨率为20 μs的M扫描（M-scan）数据，同时通过神经袖套采集神经电活动信号。本次实验共纳入10只大鼠作为实验对象：其中3只为未施加刺激的对照组，3只接受爪部刺激，剩余4只接受神经直接刺激。对每只大鼠的OCT信号强度、相位延迟、相位及频谱变化进行量化计算，并与对照组大鼠以及溶液中微球和镜面参考样本的噪声水平进行对比分析。
主要结果：观测到的相位延迟与相位变化未超出镜面参考样本的噪声水平。在3只爪部刺激样本与2只神经刺激样本中，其信号强度变化以及2只爪部刺激样本的频谱振幅变化均超出参考噪声水平。信号强度与频谱振幅变化的延迟启动时间与持续时长，与有髓神经纤维因钾离子电流引发的渗透性肿胀在时间上具有一致性——该现象此前已通过光散射技术在鱿鱼和螃蟹神经中得到表征，但目前尚未见利用OCT对有髓神经纤维开展此类研究的相关报道。
研究意义：利用OCT信号强度与频谱对神经组织中的渗透性肿胀进行成像，为外周神经与大脑白质的功能成像开辟了极具前景的新途径。