Tegeler C, Strother S C, Anderson J R, Kim S G
Center for Magnetic Resonance Research, Medical School, University of Minnesota, Minneapolis, USA.
Hum Brain Mapp. 1999;7(4):267-83. doi: 10.1002/(sici)1097-0193(1999)7:4<267::aid-hbm5>3.0.co;2-3.
The reproducibility of activation patterns in the whole brain obtained by functional magnetic resonance imaging (fMRI) experiments at 4 Tesla was studied with a simple finger-opposition task. Six subjects performed three runs in one session, and each run was analyzed separately with the t-test as a univariate method and Fisher's linear discriminant analysis as a multivariate method. Detrending with a first- and third-order polynomial as well as logarithmic transformation as preprocessing steps for the t-test were tested for their impact on reproducibility. Reproducibility across the whole brain was studied by using scatter plots of statistical values and calculating the correlation coefficient between pairs of activation maps. In order to compare reproducibility of "activated" voxels across runs, subjects and models, 2% of all voxels in the brain with the highest statistical values were classified as activated. The analysis of reproducible activated voxels was performed for the whole brain and within regions of interest. We found considerable variability in reproducibility across subjects, regions of interest, and analysis methods. The t-test on the linear detrended data yielded better reproducibility than Fisher's linear discriminant analysis, and therefore seems to be a robust although conservative method. Preliminary data indicate that these modeling results may be reversed by preprocessing to reduce respiratory and cardiac physiological noise effects. The reproducibility of both the position and number of activated voxels in the sensorimotor cortex was highest, while that of the supplementary motor area was much lower, with reproducibility of the cerebellum falling in between the other two areas.
通过4特斯拉的功能磁共振成像（fMRI）实验获得的全脑激活模式的可重复性，采用简单的手指对指任务进行了研究。6名受试者在一个实验环节中进行了3次扫描，每次扫描分别采用t检验作为单变量方法和Fisher线性判别分析作为多变量方法进行分析。测试了使用一阶和三阶多项式去趋势以及对数变换作为t检验的预处理步骤对可重复性的影响。通过统计值的散点图以及计算激活图对之间的相关系数，研究了全脑的可重复性。为了比较各次扫描、受试者和模型之间“激活”体素的可重复性，将大脑中统计值最高的所有体素的2%归类为激活体素。对全脑以及感兴趣区域内的可重复激活体素进行了分析。我们发现，受试者、感兴趣区域和分析方法之间的可重复性存在很大差异。对线性去趋势数据进行t检验产生的可重复性比Fisher线性判别分析更好，因此似乎是一种稳健但保守的方法。初步数据表明，这些建模结果可能会因预处理以减少呼吸和心脏生理噪声影响而反转。感觉运动皮层中激活体素的位置和数量的可重复性最高，而辅助运动区的可重复性则低得多，小脑的可重复性介于其他两个区域之间。
