Reliability-based voxel selection

While functional magnetic resonance imaging (fMRI) studies typically measure responses across the whole brain, not all regions are likely to be informative for a given study. Which voxels should be considered? Here we propose a method for voxel selection based on the reliability of the data. This method isolates voxels that respond consistently across imaging runs while maximizing the reliability of multi-voxel patterns across the selected voxels. We estimate that it is suitable for designs with at least 15 conditions. In two example datasets, we found that this proposed method defines a smaller set of voxels than another common method, activity-based voxel selection. Broadly, this method eliminates the need to define regions or statistical thresholds a priori and puts the focus on data reliability as the first step in analyzing fMRI data. •When predicting and mapping voxel responses, which cortex should be considered?•We introduce a method to isolate cortex that responds reliably across fMRI runs.•This method is suitable for condition-rich designs with at least 15 conditions.•Notably, it puts the focus on reliability as the first stage of fMRI data analysis.