Abstract
Previous cross-sectional magnetic resonance imaging (MRI) studies of healthy aging in young adults have indicated the presence of significant inverse correlations between age and gray matter volumes, although not homogeneously across all brain regions. However, such cross-sectional studies have important limitations and there is a scarcity of detailed longitudinal MRI studies with repeated measures obtained in the same individuals in order to investigate regional gray matter changes during short periods of time in non-elderly healthy adults. In the present study, 52 healthy young adults aged 18 to 50 years (27 males and 25 females) were followed with repeated MRI acquisitions over approximately 15 months. Gray matter volumes were compared between the two times using voxel-based morphometry, with the prediction that volume changes would be detectable in the frontal lobe, temporal neocortex and hippocampus. Voxel-wise analyses showed significant (P < 0.05, family-wise error corrected) relative volume reductions of gray matter in two small foci located in the right orbitofrontal cortex and left hippocampus. Separate comparisons for males and females showed bilateral gray matter relative reductions in the orbitofrontal cortex over time only in males. We conclude that, in non-elderly healthy adults, subtle gray matter volume alterations are detectable after short periods of time. This underscores the dynamic nature of gray matter changes in the brain during adult life, with regional volume reductions being detectable in brain regions that are relevant to cognitive and emotional processes.
Highlights
Studies of the processes of development and aging of the normal brain are important to increase knowledge about the physiological bases of brain functioning, and to help clarify the pathophysiology of neurological and psychiatric disorders
While some groups propose that the aging process is mainly characterized by changes in white matter associated with subcortical neuronal loss [7], others suggest that the effects of aging are primarily and substantially reflected in alterations in the volume of cortical gray matter regions [4,8]
For the subgroup older than 30 years (N = 23). These analyses showed no brain areas of relative volume decrease or increase in either of these two subgroups over time. This longitudinal magnetic resonance imaging (MRI) study investigated the presence of gray matter volume loss over time in a sample of non-elderly healthy adults, with morphometric brain measurements separated by an average of approximately 15 months
Summary
Studies of the processes of development and aging of the normal brain are important to increase knowledge about the physiological bases of brain functioning, and to help clarify the pathophysiology of neurological and psychiatric disorders. While some groups propose that the aging process is mainly characterized by changes in white matter associated with subcortical neuronal loss [7], others suggest that the effects of aging are primarily and substantially reflected in alterations in the volume of cortical gray matter regions [4,8]. Most researchers worldwide agree that both gray and white matter changes are important in the aging process. There is evidence that volumetric alterations of gray matter associated with the process of brain aging occur differently according to the stage of life (childhood, adolescence, adulthood, or elderly life) [8] and between females and males [9,10]
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