Changes in Diffusion Tensor Imaging characteristics of cortical and subcortical GM regions have also been recently reported and various mechanisms involving structural and physiological characteristics have been proposed (Camara et al., 2007, Douaud et al., 2009, Hasan et al., 2009, Lebel et al., 2008, Pfefferbaum et al., 2010a, Wang et al., 2010a, Zhan et al., 2012, Zhao et al., 2012). Specific examples of increased anisotropy include, loss of myelinated fibers passing through GM structures (Douaud et al., 2009), targeted loss of certain dendritic connections (Hasan et al., 2008), and aging-related neural and dendritic elimination, (Hasan et al., 2009), tissue compaction and gliosis, (Wang et al., 2010b), and iron deposition (Pfefferbaum et al., 2010a). Rulseh et al. (2013) reported iron-dependent signal attenuation in vitro (resulting in increased FA) as well as an apparent FA increase and mean diffusivity decrease in vivo as signal attenuated in putamen and concluded that ferritin-bound iron makes an important contribution to DTI metrics in low-signal, isotropic, iron-rich regions. Specifically, it is likely that the apparent increase in FA with age in bilateral putamen may be due
