Neuroscientists at Johns Hopkins University worked with laboratory mice to identify the brain mechanism responsible for a common age-related memory loss This work was published in current biology in May. It provides new insights into the operation of aging brain and may deepen our understanding of Alzheimer's disease and similar human diseases.
"We are trying to understand normal memory and why a part of the brain called the hippocampus is so critical to normal memory," said James knierim, the study's lead author. "But there are also many memory disorders, and there is something wrong with this area." He is a professor at the zanvyl Krieger Institute of mind / brain at the University.
Neuroscientists know that neurons in the hippocampus, located deep in the temporal lobe of the brain, are responsible for a complementary pair of memory functions called pattern separation and pattern completion. These functions occur in a gradient fashion in a tiny region of the hippocampus called CA3.
When these functional swings lose balance, memory will be impaired, leading to forgetting or repeating their own symptoms. Researchers at Johns Hopkins University found that as the brain ages, this imbalance may be caused by the disappearance of the CA3 gradient. In addition, the pattern separation function gradually disappears and the pattern completion function takes its place.
Neurons responsible for pattern separation are generally more common in the proximal region of CA3 region, while neurons responsible for pattern completion are common in the distal region. Heekyung Lee, an assistant research scientist from the Institute of mind / brain research, pointed out that with age, neural activity in the proximal region becomes hyperactive, and the interaction between the two regions becomes abnormal, resulting in an advantage in pattern completion.
In the normal brain, pattern separation and pattern completion work together. They classify and understand perception and experience from the most basic to highly complex. If you go to a restaurant with your family, and you go to the same restaurant with your friends a month later, you should be able to recognize that it is the same restaurant, even if some details have changed -- this is the completion of the model. But you also need to remember which conversation happened and when, so that you don't confuse the two experiences -- this is pattern separation.
When pattern separation disappears, pattern completion will overwhelm the whole process. Because the brain focuses on the common experience of the restaurant and excludes the details of the individual interview, you may remember the conversation about a trip to Italy in an interview, but you make a mistake who is talking. "We all make these mistakes, but they tend to get worse with age," says knierim
In the experiment, the scientists compared the young rats with unaffected memory with the old rats with unaffected memory and the old rats with affected memory. Although the old rats with undamaged memory completed the water maze task as the young rats, the neurons in the CA3 region of their hippocampus have begun to tend to complete the pattern at the expense of pattern separation. Since haircuts have not been shown in their behavior in this lifetime, the researchers concluded that there is something that allows the experimental rats to compensate for this defect.
The researchers point out that this finding has been echoed in humans, who are still surprisingly sharp in their old age. Therefore, determining the mechanism of memory loss can lay a foundation for understanding what can prevent some human memory damage, and then understand how to prevent or delay cognitive decline in the elderly.
"If we can better understand what these compensation mechanisms are, maybe we can help prevent cognitive decline with age," knierim said. "Or, if we can't stop it, maybe we can strengthen other parts of the brain to compensate for the loss that is happening."