Brain Imaging Centre, Research Centre for Natural Sciences, Budapest, Hungary.
Laboratory for Social and Neural Systems Research, University of Zürich, Rämistrasse 100, P.O. Box 149, Zürich, Switzerland.
MAGMA. 2021 Oct;34(5):667-676. doi: 10.1007/s10334-021-00918-z. Epub 2021 Mar 25.
There is a tendency for reducing TR in MRI experiments with multi-band imaging. We empirically investigate its benefit for the group-level statistical outcome in task-evoked fMRI.
Three visual fMRI data sets were collected from 17 healthy adult participants. Multi-band acquisition helped vary the TR (2000/1000/410 ms, respectively). Because these data sets capture different temporal aspects of the haemodynamic response (HRF), we tested several HRF models. We computed a composite descriptive statistic, H, from β's of each first-level model fit and carried it to the group-level analysis. The number of activated voxels and the t value of the group-level analysis as well as a goodness-of-fit measure were used as surrogate markers of data quality for comparison.
Increasing the temporal sampling rate did not provide a universal improvement in the group-level statistical outcome. Rather, both the voxel-wise and ROI-averaged group-level results varied widely with anatomical location, choice of HRF and the setting of the TR. Correspondingly, the goodness-of-fit of HRFs became worse with increasing the sampling frequency.
Rather than universally increasing the temporal sampling rate in cognitive fMRI experiments, these results advocate the performance of a pilot study for the specific ROIs of interest to identify the appropriate temporal sampling rate for the acquisition and the correspondingly suitable HRF for the analysis of the data.
在多带成像的 MRI 实验中，存在降低重复时间（TR）的趋势。我们通过实证研究，考察了其对任务诱发 fMRI 的组水平统计结果的益处。
从 17 名健康成年参与者中收集了三个视觉 fMRI 数据集。多带采集有助于改变 TR（分别为 2000/1000/410ms）。由于这些数据集捕捉了血流动力学反应（HRF）的不同时间方面，我们测试了几种 HRF 模型。我们从每个一级模型拟合的β计算了一个综合描述性统计量 H，并将其带到组水平分析中。激活体素的数量和组水平分析的 t 值以及拟合优度度量被用作比较的数据质量替代标志物。
增加时间采样率并没有普遍提高组水平的统计结果。相反，无论是基于体素还是 ROI 的组水平结果，都因解剖位置、HRF 的选择和 TR 的设置而变化很大。相应地，随着采样频率的增加，HRF 的拟合优度变得更差。
在认知 fMRI 实验中，不是普遍增加时间采样率，而是提倡针对特定感兴趣 ROI 进行试点研究，以确定适当的时间采样率和适合数据分析的相应合适的 HRF。
