Background: The mean diffusivity (MD) parameter obtained by diffusion tensor imaging
provides a measure of how freely water molecules move in brain tissue. Greater tissue density
conferred by closely arrayed cellular structures is assumed to lower MD by inhibiting the free diffusion
of water molecules.
Methods: In this paper, we review studies showing MD variation among regions of the brain dopaminergic
system (MDDS), especially subcortical structures such as the putamen, caudate nucleus,
and globus pallidus, in different conditions with known associations to dopaminergic system function
or dysfunction. The methodologies and background related to MD and MDDS are also discussed.
Results: Past studies indicate that MDDS is sensitive to pathological derangement of dopaminergic
activity, neural changes caused by cognitive and pharmacological interventions that are known to
affect the dopaminergic system, and individual character traits related to dopaminergic function.
Conclusion: These results suggest that MDDS can be one useful tool to tap the neural differences
related to the dopaminergic system.