Models

caudateModel <- gam(caudateR2star ~ s(age) + sex + caudateCBF, data=r2star, method="REML")
pallidumModel <- gam(pallidumR2star ~ s(age) + sex + pallidumCBF, data=r2star, method="REML")
putamenModel <- gam(putamenR2star ~ s(age) + sex + putamenCBF, data=r2star, method="REML")

##   summary(caudateModel)$p.table[3, 4]
## 1                           0.2622916

##   summary(pallidumModel)$p.table[3, 4]
## 1                            0.8313393

##   summary(putamenModel)$p.table[3, 4]
## 1                          0.01027766