According to a new study at the University of California - Los Angeles Health Sciences, our brains record a group store of memories, instead of single memories. So, recollecting one significant memory could trigger an individual to recall others connected by time. As we age, our brains gradually lose their ability to link related memories.
UCLA researchers have discovered a key molecular mechanism behind memory linking. They’ve also identified a way to restore this brain function in middle-aged mice - and an FDA-approved drug that achieves the same thing. Published in Nature, the findings suggest a new method for strengthening human memory in middle age and a possible early intervention for dementia.
A distinguished professor of neurobiology and psychiatry at the David Geffen School of Medicine at UCLA, Alcino Silva said, “The ability to link related experiences teaches how to stay safe and operate successfully in the world.”
In the current study, Silva and his colleagues discovered a central mechanism underlying mice's ability to link their memories of two different cages. A tiny microscope opened a window into the animals' brains, enabling the scientists to observe neurons firing and creating new memories.
Boosting CCR5 gene expression in the brains of middle-aged mice interfered with memory linking. The animals forgot the connection between the two cages. When the scientists deleted the CCR5 gene in the animals, the mice were able to link memories that normal mice could not. Silva had previously studied the drug, maraviroc, which the U.S. Food and Drug Administration approved in 2007 for the treatment of HIV infection. His lab discovered that maraviroc also suppressed CCR5 in the brains of mice.
"When we gave maraviroc to older mice, the drug duplicated the effect of genetically deleting CCR5 from their DNA," said Silva, a member of the UCLA Brain Research Institute. "The older animals were able to link memories again.”
The finding suggests that maraviroc could be used off-label to help restore middle-aged memory loss, as well as reverse the cognitive deficits caused by HIV infection. "Our next step will be to organize a clinical trial to test maraviroc's influence on early memory loss with the goal of early intervention," said Silva. "Once we fully understand how memory declines, we possess the potential to slow down the process."
"Life would be impossible if we remembered everything," said Silva. "We suspect that CCR5 enables the brain to connect meaningful experiences by filtering out less significant details." The National Institute on Aging funded the research.
