July 1, 2022 – Johns Hopkins scientists have identified age-related brain mechanisms memory lossexpanding our knowledge of the inner workings of the aging brain and potentially opening the door to new Alzheimer’s treatments.
The researchers looked at the hippocampus, a part of the brain thought to store long-term memories.
The neurons there are responsible for a pair of memory functions — called pattern separation and pattern completion — that work together in a young, healthy brain. These functions can get out of balance with age, affecting memory.
The Johns Hopkins team may have discovered the cause of this imbalance.Their findings – reported in New paper in the journal Current Biology – not only help us improve Dementia Treatmentbut the researchers say the loss of thinking ability can even be prevented or delayed in the first place.
Pattern separation and pattern completion
To understand how the hippocampus changes with age, the researchers looked at the brains of mice. In rats and humans, pattern separation and pattern completion exist, controlled by neurons in the hippocampus.
As the name suggests, pattern completion is when you record some detail or piece of information—the note of some music, or the beginning of a famous movie line—and then your brain retrieves the full memory. Pattern separation, on the other hand, is able to distinguish similar observations or experiences (such as visiting the same restaurant twice) and store them as separate memories.
These functions occur along the gradient of a tiny region called CA3.This gradient disappears with age, study finds, lead study authors say Dr. Hey-Kyoung Lee, assistant research scientist at the university’s Zanvyl Krieger Mind/Brain Institute. “The main consequence of the loss,” Lee said, “is that pattern completion becomes more dominant in rats with age.”
what’s going on in the brain
Neurons responsible for pattern completion occupy the “distal” end of CA3, while neurons responsible for pattern separation are located on the “proximal” end. Lee said that previous studies did not examine the proximal and distal regions separately, as she and her team did in this study.
Surprisingly, Lee said, “senescence hyperactivity was observed in the proximal region of CA3, rather than the expected distal region.” Contrary to their expectations, hyperactivity did not enhance the function of this region, but frustrated it. So: “Mode separation is reduced and mode completion is enhanced,” Lee said.
As pattern completion dominates, pattern separation fades away, Lee said. This may make it harder for older adults to distinguish between memories — they may recall a certain restaurant they went to, but not be able to differentiate between what happened during one visit and another.
Why do some older people stay sharp?
But this memory impairment didn’t happen to everyone, and it didn’t happen to all mice. In fact, the researchers found that some older mice performed the same spatial learning task as younger mice — even though their brains had begun to support pattern completion.
If we can better understand why this happens, we may discover new treatments for age-related memory loss, Lee said.
Co-author Michela Gallagher’s team previously demonstrated that anti-epilepsy The drug levetiracetam improves memory by reducing hyperactivity in the hippocampus.
Lee speculates that the extra detail the study adds may allow scientists to better target such drugs in the future. “This will give us more control over where we can target the deficits we see.”