“…DTI metrics have identified significant effects of adult aging that are now well described in regional white matter (for review, . Typically, with advancing age anisotropy declines and diffusivity increases more in anterior than posterior brain regions, whether measured with a region-ofinterest approach (Head et al, 2004;Madden et al, 2004;O'Sullivan et al, 2001;Pfefferbaum et al, 2005;Pfefferbaum et al, 2006;Pfefferbaum and Sullivan, 2003;Pfefferbaum et al, 2000;Salat et al, 2005;Sullivan et al, 2001), voxel-based analysis (Grieve et al, 2007;Kochunov et al, 2007;Snook et al, 2007), or quantitative fiber tracking (Pfefferbaum et al, 2007;Sullivan et al, , 2008. As observed postmortem, a predilection of age-related loss occurs for thin, unmyelinated fibers, which are in greatest abundance in the frontal lobes (Aboitiz et al, 1996;Bartzokis, 2004).…”