Aging of the mesolimbic tract in the human brain: A diffusion tensor imaging study

Area of Science:

• Neuroscience
• Neuroimaging
• Aging Research

Background:

• The mesolimbic tract (MLT) is a key dopaminergic pathway involved in reward processing, incentive salience, and social stimuli.
• Understanding age-related changes in neural pathways is crucial for explaining cognitive and social declines associated with aging.

Purpose of the Study:

• To investigate the aging process of the mesolimbic tract (MLT) in healthy human participants.
• To correlate structural changes in the MLT with age using diffusion tensor imaging and tractography.

Main Methods:

• Diffusion tensor imaging (DTI) and probabilistic tractography were used to reconstruct MLTs in 57 healthy participants across six age groups.
• MLTs were defined by fibers connecting the ventral tegmental area and nucleus accumbens.
• Voxel number (VN) and apparent diffusion coefficient (ADC) were analyzed in relation to age.

Main Results:

• A significant negative correlation was found between age and MLT voxel number (VN), indicating structural reduction with age.
• A significant positive correlation was observed between age and MLT apparent diffusion coefficient (ADC), suggesting microstructural changes.
• MLT VN was significantly lower and ADC significantly higher in older age groups (60s and 70s) compared to younger groups.

Conclusions:

• MLT aging begins as early as the 20s or 30s and progresses throughout life.
• Significant degeneration of the MLT is evident by the 60s.
• Age-related MLT degeneration may underlie declines in memory and social interaction observed in normal aging.