Activation pattern reproducibility: measuring the effects of group size and data analysis models.

The reproducibility of patterns from brain activation experiments has been examined only for suprathreshold spatially localized foci. Scatter plots comparing signal levels across all pairs of Talairach voxels for pairs of functional activation images provide an alternative approach for assessing reproducibility. Image-wide, signal-level reproducibility may be quantitatively summarized using pattern similarity measures such as the Pearson product-moment correlation, rho. Empirical population distributions of rho for many pair-wise image comparisons, generated using statistical resampling techniques, may be used to examine the impact of a wide range of experimental variables. We demonstrate the use of such empirical rho-histograms to measure changes in reproducibility for [(15)O]-water PET scans of a simple motor task as a function of group size and data analysis model.