Department of Radiology, UMDNJ-New Jersey Medical School, Newark, NJ 07103, USA.
Magn Reson Imaging. 2011 Jan;29(1):140-6. doi: 10.1016/j.mri.2010.07.006. Epub 2010 Sep 15.
Block and event-related stimulus designs are typically used in fMRI studies depending on the importance of detection power or estimation efficiency. The extent of vascular contribution to variability in block and event-related fMRI-BOLD response is not known. With scaling, the extent of vascular variability in the fMRI-BOLD response during block and event-related design tasks was investigated. Blood oxygen level-dependent (BOLD) contrast data from healthy volunteers performing a block design motor task and an event-related memory task requiring performance of a motor response were analyzed from the regions of interest (ROIs) surrounding the primary and supplementary motor cortices. Average BOLD signal change was significantly larger during the block design compared to the event-related design. In each subject, BOLD signal change across voxels in the ROIs had higher variation during the block design task compared to the event-related design task. Scaling using the resting state fluctuation of amplitude (RSFA) and breath-hold (BH), which minimizes BOLD variation due to vascular origins, reduced the within-subject BOLD variability in every subject during both tasks but significantly reduced BOLD variability across subjects only during the block design task. The strong non-neural source of intra- and intersubject variability of BOLD response during the block design compared to event-related task indicates that study designs optimizing for statistical power through enhancement of the BOLD contrast (for, e.g., block design) can be affected by enhancement of non-neural sources of BOLD variability.
基于检测能力或估计效率的重要性，功能磁共振成像 (fMRI) 研究中通常使用块设计和事件相关刺激设计。血管对块和事件相关 fMRI-BOLD 反应变异性的贡献程度尚不清楚。通过定标，研究了 fMRI-BOLD 响应期间块和事件相关设计任务中血管变异性的程度。分析了健康志愿者执行块设计运动任务和需要执行运动反应的事件相关记忆任务时的血氧水平依赖（BOLD）对比数据，来自初级和辅助运动皮层周围的感兴趣区域 (ROI)。与事件相关设计相比，块设计中平均 BOLD 信号变化明显更大。在每个受试者中，与事件相关设计任务相比，ROI 中体素的 BOLD 信号变化在块设计任务中具有更高的变化。使用静息状态波动幅度 (RSFA) 和屏气 (BH) 进行定标，这最小化了由于血管起源引起的 BOLD 变化，降低了每个受试者在两个任务期间的 BOLD 变异性，但仅在块设计任务期间显著降低了跨受试者的 BOLD 变异性。与事件相关任务相比，块设计中 BOLD 反应的个体内和个体间变异性的强非神经源表明，通过增强 BOLD 对比（例如，块设计）来优化统计能力的研究设计可能会受到 BOLD 变异性的非神经源增强的影响。
