Whether it is a character from a Disney movie telling you to let it go, or the Dalai Lama explaining how useless it is to worry, a new study shows that taking that advice to heart can help prevent the erosion of your memory.
A new study from researchers at Ohio State University (OSU) shows that prolonged stress breaks down memory, and the immune system plays a vital role in this cognitive impairment.
Researchers said this was the first time a study of this kind has linked chronic stress and memory. They hope this could lead to possible treatments for those exposed to long-term stress such as combat veterans, bullying victims or those with stressful jobs.
The study consisted of taking mice who had previously mastered getting out of a maze and introducing an alpha mouse into their area. The alpha mouse caused the other mice anxiety. As a result the test subjects had trouble finding the exit to the maze after being repeatedly exposed to the alpha mouse.
In a statement to the university, Jonathan Godbout, lead researcher and associate professor of neuroscience at OSU, said that the mice who were stressed by the alpha mouse had trouble finding their way out of a maze they had previously mastered. The unstressed mice, however, had no problem remembering.
Researchers said the mice also had measurable changes to their brain chemistry, including inflammation caused by the immune system. The presence of macrophages, or immune cells, were found in the brains of the stressed mice.
"The chronic stress leads to the release of inflammatory monocytes into circulation and these immune cells are recruited to the brain," Godbout said. "The recruited monocytes are now considered macrophages. The inflammation mediated by these macrophages causes anxiety and memory impairment."
"Taking macrophages out of the equation prevents stress induced prolonged anxiety and cognitive impairment," Godbout said.
The study focused on the hippocampus, a part of the brain that is responsible for emotion and memory. Researchers found that the stressed mice struggled with spatial memory, but that resolved after a 28-day period. However, the stressed mice displayed a depressive type of behavior, social avoidance, that lasted past the 28-day period.
When a chemical was given to the mice that kept the inflammation from happening, neither the social avoidance nor the brain-cell problem went away. The memory loss and the macrophages did disappear. This led the researchers to believe that the memory problems coming after prolonged stress was due to inflammation brought about by the immune system.
The research team's work appeared in The Journal of Neuroscienceand built on the connection between long-term stress and chronic anxiety.
Godbout said previous studies had shown a link between stress and memory consolidation, but the novelty of this new study is the influence of the peripheral immune system on this impairment with stress.
The research was made possible by the National Institutes of Health, The National Institute of Aging and the National Institute of Dental and Craniofacial Research
No information on competing interests was given.