Department of Neurophysiology, Juntendo University Graduate School of Medicine, Tokyo, Japan.
Neuroimage. 2011 Aug 1;57(3):991-1002. doi: 10.1016/j.neuroimage.2011.05.012. Epub 2011 May 10.
Brain activity during a verbal fluency task (VFT) has been the target of many functional imaging studies. Most studies using near-infrared spectroscopy (NIRS) have reported major activation in the frontal pole, but those using PET or fMRI have not. This led us to hypothesize that changes in the NIRS signals measured in the forehead during VFT were due to changes in skin blood flow. To test this hypothesis, we measured NIRS signals and the Doppler tissue blood flow signals in the foreheads of 50 participants. The measurements were performed while each participant produced words during two 60-s periods with an interval of 100 s. In addition to a conventional optode separation distance of 30 mm (FAR channels), we used a short distance--5mm (NEAR channels)--to measure NIRS signals that originated exclusively from surface tissues. The oxygenated hemoglobin (oxyHb) concentration in the FAR and NEAR channels, as well as the Doppler blood flow signal, increased in a similar manner during the two periods of word production; the signal increase in the first period was twice as high as that in the second period. Accordingly, the mean changes in oxyHb concentration in the FAR channels were correlated closely with the changes in the NEAR channels (R(2) = 0.91) and with the integrated Doppler skin blood flow signal (R(2) = 0.94). Furthermore, task-related NIRS responses disappeared when we blocked skin blood flows by pressing a small area that covered a pair of optodes. Additionally, changes in the FAR channel signals were correlated closely with the magnitude of pulsatile waves in the Doppler signal (R(2) = 0.92), but these signals were not highly correlated with the pulse rate (R(2) = 0.43). These results suggest that a major part of the task-related changes in the oxyHb concentration in the forehead is due to task-related changes in the skin blood flow, which is under different autonomic control than heart rate.
在言语流畅性任务（VFT）期间的大脑活动一直是许多功能成像研究的目标。大多数使用近红外光谱（NIRS）的研究报告称，额极有主要激活，但使用 PET 或 fMRI 的研究则没有。这导致我们假设在 VFT 期间在前额测量的 NIRS 信号的变化是由于皮肤血流的变化。为了验证这一假设，我们测量了 50 名参与者的前额的 NIRS 信号和多普勒组织血流信号。在每个参与者在 100 秒的间隔内进行两次 60 秒的单词生成期间进行了测量。除了常规的光极分离距离 30 毫米（FAR 通道）之外，我们还使用短距离 - 5 毫米（NEAR 通道）来测量仅源自表面组织的 NIRS 信号。在两个单词生成期间，FAR 和 NEAR 通道中的氧合血红蛋白（oxyHb）浓度以及多普勒血流信号以相似的方式增加；第一期的信号增加是第二期的两倍。因此，FAR 通道中 oxyHb 浓度的平均变化与 NEAR 通道（R² = 0.91）和整合的多普勒皮肤血流信号（R² = 0.94）的变化密切相关。此外，当我们通过按压覆盖一对光极的小区域来阻止皮肤血流时，与任务相关的 NIRS 响应消失了。此外，FAR 通道信号的变化与多普勒信号中的脉动波幅度密切相关（R² = 0.92），但这些信号与脉搏率相关性不高（R² = 0.43）。这些结果表明，额部 oxyHb 浓度与任务相关的变化的主要部分归因于皮肤血流的与任务相关的变化，其受自主神经控制而不是心率控制。
