3T hippocampal glutamate-glutamine complex reflects verbal memory decline in aging

The hippocampus is a critical site for alterations that are responsible for age-related changes in memory. Here, we present a relatively novel approach of examining the relationship between memory performance and glutamate-glutamine levels using short echo time magnetic resonance spectroscopy. Specifically, we investigated the relationship between Glx (a composite of glutamate and glutamine) levels in the hippocampus, performance on a word-recall task, and resting-state functional connectivity. While there was no overall difference in Glx intensity between young and aging adults, we identified a positive correlation between delayed word-list recall and Glx, bilaterally in older adults, but not in young adults. Collapsed across age, we also discovered a negative relationship between Glx intensity and resting-state functional connectivity between the anterior hippocampus and regions in the subcallosal gyrus. These findings demonstrate the possible utility of Glx in identifying age-related changes in the brain and behavior and provide encouragement that magnetic resonance spectroscopy can be useful in predicting age-related decline before any physical abnormalities are present.