My "default" cortical parcellation is the 400 parcels by 7 networks version of Schaefer2018. I like these parcellations because they're available in all the spaces we use (volume, fsaverage, fsLR (HCP)) and are independent from our analyses; "all parcellations are wrong, but some are useful".
The Schaefer parcellations come in several versions for each resolution, however, and a parcel described by its 7Networks number likely has a different 17Network number. Note that the parcel boundaries are the same for all same-resolution versions: there is only one set of 400 parcels, but which of those 400 parcels is #77 varies between the 7 and 17 network versions. This post describes how to translate parcel numbers between network versions, using a bit of (base) R code.
Logic: since there is only one set of parcels at each resolution, there is only one set of centroid coordinates at each resolution. Thus, we can match parcels across network orderings by centroids.
First, set sch.path to the location of your copy of the Schaefer2018 Parcellations directory and load the 7 and 17 network files: (apologies for the wonky code formatting)
cen7.tbl <- read.csv(paste0(sch.path, "MNI/Centroid_coordinates/Schaefer2018_400Parcels_7Networks_order_FSLMNI152_1mm.Centroid_RAS.csv"));
cen17.tbl <- read.csv(paste0(sch.path, "MNI/Centroid_coordinates/Schaefer2018_400Parcels_17Networks_order_FSLMNI152_1mm.Centroid_RAS.csv"));
Next, make vectors for translating the 7Network number to the 17Network number (and the reverse):
x17to7 <- rep(NA, nrow(cen7.tbl));
for (i in 1:nrow(cen7.tbl)) {
x7to17[i] <- which(cen17.tbl$R == cen7.tbl$R[i] & cen17.tbl$A == cen7.tbl$A[i] & cen17.tbl$S == cen7.tbl$S[i]);
x17to7[i] <- which(cen7.tbl$R == cen17.tbl$R[i] & cen7.tbl$A == cen17.tbl$A[i] & cen7.tbl$S == cen17.tbl$S[i]);
}
Now the vectors can be used to translate parcel numbers: parcel #77 in the 7Networks ordering is parcel #126 in the 17Networks ordering.
# ROI.Label ROI.Name R A S
#77 77 7Networks_LH_DorsAttn_Post_9 -33 -46 41
# ROI.Label ROI.Name R A S
#126 126 17Networks_LH_ContA_IPS_5 -33 -46 41
Note that the parcel's R A S coordinates are the same, but its name and label (number) vary between the two network versions.
