Institute for Biodiagnostics-Atlantic, National Research Council, Halifax, NS B3H 3A7, Canada.
BMC Neurosci. 2012 Aug 1;13:91. doi: 10.1186/1471-2202-13-91.
There is growing evidence for the idea of fMRI activation in white matter. In the current study, we compared hemodynamic response functions (HRF) in white matter and gray matter using 4 T fMRI. White matter fMRI activation was elicited in the isthmus of the corpus callosum at both the group and individual levels (using an established interhemispheric transfer task). Callosal HRFs were compared to HRFs from cingulate and parietal activation.
Examination of the raw HRF revealed similar overall response characteristics. Finite impulse response modeling confirmed that the WM HRF characteristics were comparable to those of the GM HRF, but had significantly decreased peak response amplitudes.
Overall, the results matched a priori expectations of smaller HRF responses in white matter due to the relative drop in cerebral blood flow (CBF) and cerebral blood volume (CBV). Importantly, the findings demonstrate that despite lower CBF and CBV, white matter fMRI activation remained within detectable ranges at 4 T.
越来越多的证据支持 fMRI 在白质中激活的观点。在当前的研究中，我们使用 4T fMRI 比较了白质和灰质中的血液动力学反应函数（HRF）。通过使用已建立的半球间转移任务，在胼胝体峡部在群体和个体水平上引发了白质 fMRI 激活。将胼胝体 HRF 与扣带回和顶叶激活的 HRF 进行了比较。
对原始 HRF 的检查显示出相似的整体反应特征。有限脉冲响应建模证实，WM HRF 特征与 GM HRF 相当，但峰值响应幅度明显降低。
总体而言，结果与由于脑血流量（CBF）和脑血容量（CBV）相对下降导致白质 HRF 响应较小的先验预期相符。重要的是，这些发现表明，尽管 CBF 和 CBV 较低，但在 4T 时，白质 fMRI 激活仍处于可检测范围内。
