Diffusion tensor metrics, T₂ relaxation, and volumetry of the naturally aging human caudate nuclei in healthy young and middle-aged adults: Possible implications for the neurobiology of human brain aging and disease

In this study of a cohort of 33 young and middle-age adults (19-59 years) we report simultaneous measurements of normal age-related changes in the caudate nuclei volume, diffusion tensor metrics, and T₂ relaxation time. Both the absolute caudate volume and its ratio relative to the total intracranial volume decreased rapidly with age in both men and women (r = -0.55; P < 0.001). The fractional diffusion tensor anisotropy of the caudate nuclei increased with age in both males and females (r = 0.48; P = 0.005). The corresponding age correlations of the caudate axial (r = 0.17; P = 0.35), transverse (r = -0.12; P = 0.50), mean diffusivities (r = 0.018; P = 0.92), and T₂ relaxation times (r = 0.194; P = 0.28) were weaker and did not reach statistical significance (P > 0.05). Our preliminary findings warrant further studies on the older and aging adults and indicate that caudate diffusion tensor imaging-derived metrics can be used as surrogates in modeling the neuronal substrates of gray matter atrophy.