Age and gender predict volume decline in the anterior and posterior hippocampus in early adulthood.

Magnetic Resonance Imaging (MRI) provides a noninvasive method for investigating brain morphology. Within the medial temporal lobe, special attention has been paid to the hippocampus (HC) and amygdala (AG) because of their role in memory, depression, emotion, and learning. Volume changes in these areas have been observed in conjunction with certain disease states, e.g. Alzheimer's disease, post-traumatic stress disorder, and depression. Aging has also been shown to result in gray matter volume loss of the overall brain, including the HC. With regard to gender specificity, results suggest a larger shrinkage for men of brain gray matter, with controversial observations being made for the HC. With recently refined MRI acquisition and segmentation protocols, the HC and AG of 80 subjects in early adulthood (39 men and 41 women, age 18-42 years) were investigated. Whereas the volume of the AG appeared to be independent of age and gender, a significant negative correlation with age for both left and right HC was found in men (r = -0.47 and -0.44, respectively) but not in women (r = 0.01 and 0.02, respectively). The volume decline in men appeared to be linear, starting at the beginning of the third life decade and approximating 1.5% per annum. Using voxel-based regressional analysis, it was shown that changes with age occurred mostly in the head and tail of the HC. This finding underscores the need to include sociodemographic variables in functional and anatomical MRI designs.