Reproducibility of fMRI: Effect of the use of contextual information

We studied the effect of use of contextual information on the reproducibili ty of the results in analysis of fMRI data. We used data from a repeated si mple motor fMRI experiment, In the first approach, statistical parametric m aps were computed from a spatially unsmoothed data and thresholded using a Bonferroni corrected threshold. In the second approach, the maps were compu ted from a spatially unsmoothed data but were segmented into nonactive and active regions using a spatial contextual clustering method. In the third a pproach, the statistical parametric maps were computed from spatially smoot hed data and thresholded, using, optionally, a spatial extent threshold. Th e variation in the classification was largest in the Bonferroni thresholded statistical parametric maps. There were no significant differences in vari ation between statistical parametric maps generated with all the other meth ods. In addition to reproducibility, the detection rates of weak simulated activations in the presence of measured scanner and physiological noise wer e investigated. Contextual clustering method was the most sensitive method, while the least sensitive method was the Bonferroni corrected thresholding . Using simulated data, we demonstrated that the contextual clustering meth od preserves the shapes of activation regions better than the method using spatial smoothing of the data. (C) 2001 Academic Press.