Why do we get more forgetful as we age?

A study published by Dr. Helfrich and colleagues suggests that sleep and long-term memory are connected. Our brains don’t rest while we sleep. Instead, the neurons continue working, sending electrical waves to each other. A full night’s rest is, therefore, necessary for the good functioning of the brain waves. When we don’t sleep properly, these brain waves can’t interact properly, which will have a direct impact on our brain’s ability to store long-term memories.

However, as we get older, our ability to have a full night’s sleep reduces. Consequently, the older the brain gets, the less capacity it has to store new information and memories.

“(…) part of the brain that makes slow oscillations—and long-term memories—was smaller in older participants, suggesting that older adults are more forgetful because this region atrophies over time.”

Dr. Helfrich and colleagues found out that, as people age, two kinds of brain waves (slow oscillations, large undulations that promote restorative sleep, and sleep spindles, transient bursts of short waves) become more and more desynchronized, affecting the communication between the prefrontal cortex (where long-term memories are stored) and the hippocampus (where new information is stored at first). This break up in communication, says the researchers, tends to be more pronounced in older people. Several volunteers, between 20 and 70 years of age, had their brains scanned using structural magnetic resonance imaging while performing simple memory tests.  The results showed the part of the brain that makes slow oscillations – and long-term memories – seems to be smaller in older participants, which could indicate that this area of the brain suffers atrophy as we age.

“That atrophy is enough to impair the mechanism to bring the brain waves together in time to really store memories overnight,” Helfrich says.

But aging should not look so dire!

This research also opens the possibilities of new memory therapies and sleeping disorder treatments that can directly target the brain area where our memories are formed and stored, with increased rate of success, including in the fight to prevent neurodegenerative diseases such as Alzheimer’s.

References

Old Brains Come Uncoupled in Sleep: Slow Wave-Spindle Synchrony, Brain Atrophy, and Forgetting. Randolph F. HelfrichBryce A. Mander, William J. Jagust, Robert T. Knight, Matthew P. Walker. (2017) DOI: http://dx.doi.org/10.1016/j.neuron.2017.11.020

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