Why does our ability to remember fail as we age? Is age-related memory loss normal, or a sign of something worse, like Alzheimer’s disease? A new study in rats suggests that part of the answer may rest on how effectively different parts of the aging brain ‘talk’ to each other. This has been a difficult problem to study in people because the earliest brain changes in Alzheimer’s disease can occur a decade or more before clinical symptoms. To learn more, NIA researchers teamed up with brain imaging experts at the National Institute on Drug Abuse (NIDA) to study how brain networks change during aging in rats, in the absence of neurodegenerative disease. The findings were published in the Proceedings of the National Academy of Sciences on October 10, 2016.
Led by Dr. Jessica Ash of NIA, and Dr. Hanbing Lu of NIDA, the researchers used a rat model in which—like people—some older rats develop memory impairment and others don’t. Next, functional brain imaging examined the default mode network—an interconnected group of brain regions that is active when we rest and let our minds wander or daydream. There were two main findings. First, a dramatic loss of neural network connectivity between brain regions was found in older rats with memory impairment compared with young rats. Second, and perhaps more important, the brains of cognitively healthy older rats displayed a distinct neural network signature, different than the pattern in either young rats or older rats with memory impairment. These findings suggest that healthy cognitive aging is not simply a matter staying young, but may depend on successful network remodeling in the aged brain.
The study also suggests that interventions aimed at engaging the brain’s ability for adaptive change may help promote optimally healthy cognitive aging. Further research will be needed to see how these insights might apply in the investigation of cognitive impairment in older people.
Reference: Ash, J.A. et al. Functional connectivity with the retrosplenial cortex predicts cognitive aging in rats. PNAS. Published online Oct. 10, 2016.