Department of Veterans Affairs Health Care System, The Neuroimaging Research Group, Brain Sciences Center, Minneapolis, MN, 55417, USA.
Department of Neuroscience, University of Minnesota Medical School, Minneapolis, MN, 55455, USA.
Exp Brain Res. 2022 Aug;240(7-8):1967-1977. doi: 10.1007/s00221-022-06382-y. Epub 2022 May 18.
Blood oxygen level dependent (BOLD) signal in functional magnetic resonance imaging (fMRI) is frequently used as a proxy for underlying neural activity. Although this is a plausible assumption for experiments where a task is performed, it may not hold to the same degree for conditions of fMRI recording in a task-free, "resting" state where neural synaptic events are weak and, hence, neurovascular coupling and endothelial vascular factors become more prominent (Hillman Annu Rev Neurosci 37:161-181, 2014, 10.1146/annurev-neuro-071013-014111). Here we investigated the magnitude of change of BOLD in consecutive samples over the acquisition time period (turnover of BOLD, "TBOLD") by first-order differencing of single-voxel BOLD time series acquired in 70 areas of the cerebral cortex of 57 cognitively healthy women in a task-free resting state. More specifically, we evaluated (a) the variation of TBOLD among different cortical areas, (b) its dependence on age, and (c) its dependence on the presence (or absence) of the neuroprotective Human Leukocyte Antigen (HLA) gene DRB113 (DRB113:02 and DRB113:01). We found that TBOLD (a) varied substantially by 2.2 × among cortical areas, being highest in parahippocampal and entorhinal areas and lowest in parietal-occipital areas, (b) was significantly reduced in DRB113 carriers across cortical areas (from ~ 15% reduction in orbitofrontal cortex to 2% reduction in cuneus), and (c) increased with age in noncarriers of DRB113 but decreased with age in DRB113 carriers. These findings document significant dependencies of TBOLD on cortical area location, HLA DRB1*13 and age.
血氧水平依赖（BOLD）信号在功能磁共振成像（fMRI）中常被用作潜在神经活动的替代物。尽管对于执行任务的实验来说，这是一个合理的假设，但对于无任务的 fMRI 记录状态，即神经突触活动较弱，神经血管耦合和内皮血管因素变得更加突出的状态，这种假设可能并不成立（Hillman Annu Rev Neurosci 37:161-181, 2014, 10.1146/annurev-neuro-071013-014111）。在这里，我们通过对 57 名认知健康女性在无任务静息状态下大脑皮层 70 个区域的单像素 BOLD 时间序列进行一阶差分，首次研究了采集时间段内 BOLD 连续样本的变化幅度（BOLD 周转率，“TBOLD”）。更具体地说，我们评估了（a）TBOLD 在不同皮质区域之间的变化，（b）其对年龄的依赖性，以及（c）其对神经保护性人类白细胞抗原（HLA）基因 DRB113（DRB113:02 和 DRB113:01）存在（或不存在）的依赖性。我们发现，TBOLD（a）在皮质区域之间差异很大，在海马旁回和内嗅皮层区域最高，在顶枕叶区域最低；（b）在 DRB113 携带者中，跨皮质区域显著降低（从额眶回的~15%降低到楔前叶的 2%）；（c）在非 DRB113 携带者中随年龄增加而增加，但在 DRB113 携带者中随年龄增加而降低。这些发现证明了 TBOLD 与皮质区域位置、HLA DRB1*13 和年龄之间存在显著的依赖性。
