Mayhew J E, Askew S, Zheng Y, Porrill J, Westby G W, Redgrave P, Rector D M, Harper R M
Artificial Intelligence Vision Research Unit, University of Sheffield, United Kingdom.
Neuroimage. 1996 Dec;4(3 Pt 1):183-93. doi: 10.1006/nimg.1996.0069.
Imaging of scattered and reflected light from the surface of neural structures can reveal the functional architecture within large populations of neurons. These techniques exploit, as one of the principal signal sources, reflectance changes produced by local variation in blood volume and oxygen saturation related to neural activity. We found that a major source of variability in the captured light signal is a pervasive low-frequency (0.1-Hz) oscillation which apparently results from regional cerebral blood flow. This signal is present in brain parenchyma as well as the microvasculature and exhibits many characteristics of the low-frequency "vasomotion" signals observed in peripheral microcirculation. Concurrent measurements in brain with a laser Doppler flow meter contained an almost identical low-frequency signal. The presence of the 0.1-Hz oscillation in the cerebral microcirculation could underlie a portion of the previously described characteristics reported in reflected-light imaging studies. The prevalence of the oscillatory phenomena in the brain raises substantial temporal sampling issues for optical imaging and for other visualization techniques which depend on changes in regional cerebral blood dynamics, such as functional magnetic resonance imaging.
对神经结构表面散射光和反射光进行成像，可以揭示大量神经元内部的功能结构。作为主要信号源之一，这些技术利用了与神经活动相关的血容量和氧饱和度局部变化所产生的反射率变化。我们发现，捕获光信号中一个主要的变异性来源是一种普遍存在的低频（0.1赫兹）振荡，它显然是由局部脑血流引起的。这种信号存在于脑实质以及微血管系统中，并表现出在外周微循环中观察到的低频“血管运动”信号的许多特征。用激光多普勒血流仪对大脑进行同步测量时，包含一个几乎相同的低频信号。脑微循环中0.1赫兹振荡的存在可能是先前反射光成像研究中报道的部分特征的基础。大脑中振荡现象的普遍存在给光学成像以及其他依赖于局部脑血流动力学变化的可视化技术（如功能磁共振成像）带来了重大的时间采样问题。
