Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN 37232 USA.
Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN 37232 USA.
Neuroimage. 2020 Aug 1;216:116791. doi: 10.1016/j.neuroimage.2020.116791. Epub 2020 Apr 21.
In response to a flickering visual stimulus, the BOLD response in primary visual cortex varies with the flickering frequency and is maximal when it is close to 8Hz. In previous studies we demonstrated that BOLD signals in specific white matter (WM) pathways covary with the alternations between stimulus conditions in a block design in similar manner to gray matter (GM) regions. Here we investigated whether WM tracts show varying responses to changes in flicker frequency and are modulated in the same manner as cortical areas. We used a Fourier analysis of BOLD signals to measure the signal amplitude and phase at the fundamental frequency of a block-design task in which flickering visual stimuli alternated with blank presentations, avoiding the assumption of any specific hemodynamic response function. The BOLD responses in WM pathways and the primary visual cortex were evaluated for flicker frequencies varying between 2 and 14Hz. The variations with frequency of BOLD signals in specific WM tracts followed closely those in primary visual cortex, suggesting that variations in cortical activation are directly coupled to corresponding BOLD signals in connected WM tracts. Statistically significant differences in the timings of BOLD responses were also measured between visual cortex and specific WM bundles. These results confirm that when cortical BOLD responses are modulated by selecting different task parameters, relevant WM tracts exhibit corresponding BOLD signals that are also affected.
针对闪烁的视觉刺激，主要视觉皮层的 BOLD 反应随闪烁频率而变化，在接近 8Hz 时达到最大值。在之前的研究中，我们证明了特定白质 (WM) 通路中的 BOLD 信号与块设计中刺激条件之间的交替以与灰质 (GM) 区域相似的方式变化。在这里，我们研究了 WM 束是否表现出对闪烁频率变化的不同反应，以及是否以与皮质区域相同的方式进行调节。我们使用 BOLD 信号的傅立叶分析来测量在块设计任务中，当闪烁视觉刺激与空白呈现交替时，BOLD 信号的幅度和相位，该任务避免了对任何特定血流动力学响应函数的假设。评估了 WM 通路和主要视觉皮层中的 BOLD 反应，频率在 2Hz 至 14Hz 之间变化。特定 WM 束中的 BOLD 信号随频率的变化与主要视觉皮层非常接近，这表明皮质激活的变化与连接的 WM 束中的相应 BOLD 信号直接相关。还测量了视觉皮层和特定 WM 束之间 BOLD 反应时间的统计学显著差异。这些结果证实，当皮质 BOLD 反应通过选择不同的任务参数进行调节时，相关的 WM 束会表现出相应的 BOLD 信号，这些信号也会受到影响。
