The Effect of Correlation and Error Rate Specification on Thresholding Methods in fMRI Analysis

This paper reviews and compares thresholding methods for identifying active voxels in single-subject fMRI datasets. Different error rates are described which may be used to calibrate activation thresholds. We discuss methods which control each of the error rates at a pre-specified level α, including simple procedures which ignore spatial correlation among the test statistics as well as more elaborate ones which incorporate this correlation information. The operating characteristics of the methods are shown through a simulation study, indicat-ing that the error rate used has an important impact on the sensitivity of the thresholding method, but that accounting for correlation has little impact for individual voxelwise thresh-olding methods. The methods are illustrated with a real bilateral finger tapping experiment