I recently used mri_segstats to extract FA and MD as suggested here: http://freesurfer.net/fswiki/FsTutorial/Diffusion

Using the aparc+aseg and wmparc (resampled to diffusion space), I looked at some of the correlations between FA and MD in the same regions, and came across a few interesting ones.

wm_lh_entorhinal FA & wm_lh_entorhinal MD: r = 0.6, p <0.001

ctx_lh_entorhinal FA & ctx_lh_entorhinal MD: r = -0.3, p < 0.020

wm_lh_precuneus FA & wm_lh_precuneus MD: r = -0.6, p <0.001 

As I understand, a clear-cut interpretation especially with regards to FA changes is not so easy!  But could someone discuss / speculate as to why FA and MD could be positively correlated within the entorhinal WM region? That was found separately within a group of a elderly healthy controls and a group of dementia subjects.

Thank you for your time!

Best Wishes,

Elijah