Supplementary Material 1.

Delineation of an STN shown as the hyperintense region on the R2* images (left — green, right — red), progressing from the most superior tip (top) to inferior aspect (bottom) in 1 mm slices. The corresponding MT image is also shown, which helped identify the surrounding boundaries by using ITK-SNAP multisession view (STN is not visible on these images). The following boundaries were used in addition to direct visualisation on the R2* images: Inferiorly — The mid-point of the red nucleus, superior aspect of the optic tract and substantia nigra; Anteriorly — The posterolateral wall of the hypothalamus, defined as the grey matter between the mamillothalamic tract posteriorly and fornix anteriorly; Medially — The white matter situated between the thalamus and red nucleus; Laterally — The internal capsule; Superiorly — The anterior commissure.