Long-term stress damages the brain’s short-term memory system, new research finds.
Chronic stress leads to a build-up of macrophages in the the brain, researchers found.
It took four weeks for the immune response to reduce and the memory problems to resolve.
Dr Jonathan Godbout, who led the research, said:
“This is chronic stress.
It’s not just the stress of giving a talk or meeting someone new.”
For the research, a group of mice were taught a maze which led to an escape hole.
Some, however, were turned into ‘socially defeated’ mice.
This was done by repeatedly exposing them to an ‘alpha mouse’.
The idea was to mimic the kind of chronic social stress which humans might face from a nasty boss or other repeated stressful social situation.
All the mice were then exposed to an aggressive intruder, forcing them to run through the maze to the escape hole.
When the intruder came, the chronically stressed mice had difficulty remembering the route through the maze, Dr Godbout explained:
“The stressed mice didn’t recall it.
The mice that weren’t stressed, they really remembered it.”
The socially defeated mice also showed changes in their brains.
There was inflammation in the brain which was causing the short-term memory problems.
Professor John Sheridan, one of the study’s co-authors, said:
“Stress releases immune cells from the bone marrow and those cells can traffic to brain areas associated with neuronal activation in response to stress.
They’re being called to the brain, to the center of memory.”
The researchers also found that the memory problems resolved themselves in 28 days.
The mice, however, continued to show symptoms of depression and social avoidance even after this period.
When the scientists gave the mice a chemical that inhibited inflammation in the brain, the memory problems disappeared — although the depressive symptoms were not affected.
The study was published in The Journal of Neuroscience (McKim et al., 2016).
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