Stress linked to memory loss as people age
Researchers from the University of Iowa report high levels of cortisol, a stress hormone, can hinder short-time memory over time as people age. The findings were recently published in the Journal of Neuroscience.
How does stress affect the brain? It’s believed high spikes in cortisol levels gradually reduce the amount of synapses, which work in storing and remembering information, in the prefrontal cortex. As people age, the more exposure synapses have to stress, the smaller they become and eventually vanish.
Scientists compared 21 month-old rats to four-month old rats and placed them in a T-shaped maze for them to navigate. The rats had to remember which direction they took at the top of the T after 30, 60 and 120 seconds and then choose the opposite direction to get a treat.
The team found that older rats with high corticosterone levels — the human equivalent of cortisol — performed the worst, only remembering their pathway 58 percent of the time. Rats who were older and had lower corticosterone levels retraced their steps 80 percent of the time. Corticosterone levels did not, however, affect the younger rats. They then took tissue samples of the rats’ prefrontal cortex and found the rats that performed the worst had smaller and 20 percent fewer synapses than the other rats.
Researchers note stress is only one of many factors that contribute to mental decline. Targeting cortisol levels may help with future treatments of short-term memory loss.