Why can you remember the name of your childhood friend you haven't seen in years but easily forget the name of a person you just met a while ago? In other words, why are some memories stable for decades and others fade within minutes?
Using mouse models, Caltech researchers determined that strong, stable memories were encoded by teams of neurons, all firing in sync, providing redundancy, allowing these memories to be retained over time. The study has implications for understanding how memory can be affected after brain damage, such as strokes or Alzheimer's disease.
The work was carried out in the laboratory of Carlos Lois, Professor of Biology, and is described in a paper that appeared in the August 23 issue of Science Science . Lois is also a faculty member of the Tianchiao Institute of Neuroscience and Chrissy Chen at Caltech.
Led by doctoral student Walter Gonzalez, the team develops a test to study the neural activity of mice as they learn and memorize a new place. In the test, the mouse was placed in a straight enclosure about 5 feet long with white walls. Unique symbols mark different places on the walls ̵
When an animal was initially placed on the runway, he was not sure what to do and wandered left and right until it came to the sugar water. In these cases, single neurons are activated when the mouse notices a wall symbol. But on repeated experiences with the track, the mouse became acquainted with it and remembered the places of the sugar. As the mouse became more familiar, more and more neurons were activated synchronously, seeing every symbol on the wall. In essence, the mouse recognized where it was in relation to each unique symbol.
To examine how memories fade over time, the researchers then kept the mice off the runway for up to 20 days. After returning to the track, the mice, forming strong memories encoded by a larger number of neurons, quickly remembered the task. Although some neurons exhibit different activity, trace mouse memory is clearly identified in the activity analysis of large groups of neurons. In other words, the use of groups of neurons allows the brain to have excess and still recall memories, even if some of the original neurons are silent or damaged.
Gonzalez explains: "Imagine having a long and complicated story to tell. To save the story, you can tell it to five of your friends and then occasionally get together with all of them to tell the story again and help each other fill in the gaps that one has forgotten. In addition, every time you tell the story again, you could bring new friends to study and therefore help preserve and strengthen the memory. Similarly, your own neurons help each other encode memories that will persist over time. "
Memory is so fundamental to human behavior that any memory impairment can seriously affect our daily lives. Memory loss that occurs as part of normal aging can be a significant disadvantage for the elderly. memory caused by several diseases, most notably Alzheimer's disease, has devastating effects that can interfere with the most basic combinations, including recognizing relatives or remembering to return home. This work suggests that memory may fade ego faster with advancing age as memory is encoded by fewer neurons and if any of these neurons fail, memory is lost.The study suggests that one day designing treatments that could increase the recruitment of
"For years, people have known that the more you practice an action, the better the chance that you will remember it later," he says. Lois. "We now think that is likely because the more you practice action, the greater the number of neurons that encode the action. Conventional theories of the postulate of memory storage, in order to make memory more stable, require the strengthening of connections to the individual neuron. Our results suggest that an increase in the number of neurons encoding the same memory enables the memory to be preserved for longer. "
The report is entitled" Persistence of neuronal representations over time and damage in the hippocampus. "In addition to Gonzalez and Lois, the co-authors are Howen Gian students and former lab technician Anna Harutyunyan. Funding was provided by the American Heart Association, Della Martin Foundation, Burroughs Welfare Fund and the Native American Initiative .
Materials provided by California Institute of Technology Originally Posted by Laurie Dayose Note: Content may be edited for style and length A.