Functions for within-subject seed-based PLS analysis, implementing the ws-seed PLS method described in Roberts et al. (2016). Unlike standard seed PLS (as-fcMRI), which correlates seed and voxel activity across subjects, ws-seed PLS correlates seed and voxel trial-level beta estimates within each subject, then submits the resulting connectivity maps to task PLS.
Details
The approach requires trial-level activation estimates (e.g., from
fmrilss::lss()) rather than condition means. For each subject and
condition, Pearson correlations are computed between the seed region's
trial-by-trial betas and every voxel's trial-by-trial betas. The resulting
within-subject correlation maps (optionally Fisher-z transformed) are
stacked into a data matrix and analyzed with task PLS.
References
Roberts, R. P., Hach, S., Tippett, L. J., & Addis, D. R. (2016). The Simpson's paradox and fMRI: Similarities and differences between functional connectivity measures derived from within-subject and across-subject correlations. NeuroImage. doi:10.1016/j.neuroimage.2016.04.028