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Scientists Restore Memories by Getting Rid of “Noise”

Scientists Restore Memories by Getting Rid of “Noise” about undefined
Groundbreaking new research into Alzheimer’s disease reveals that the memories of Alzheimer's patients are not permanently lost, as once believed. They're still there, and they’re still active. Trouble is, specific memories can't be accessed because they're drowned out by "noise" from other neurons. Take away the interference and the patient gets the memories back. At least that's what happens in mice. Now, researchers are hopeful the technique will work in humans. Memories are lost in Alzheimer's disease because of damage to the brain, in particular, the hippocampus. When a specific area of the hippocampus, called CA1, suffers damage, it affects spatial memory, which allows you to remember how to get to work or find your way home. Researchers at the German Center for Neurodegenerative Diseases set out to observe the real-time activity of CA1 neurons in mice with the human equivalent of Alzheimer's disease.

Study Reveals Memories of Alzheimer’s Victims Still Function

Researchers gave both mice with Alzheimer's and mice with healthy brains a new environment to explore, and then measured the results with a technique called two-photon in-vivo microscopy. A few days later, they put both groups of mice back in the same environment. The healthy mice remembered their surroundings, but the Alzheimer's mice did not. They acted as the researchers expected, as if this was an entirely new experience. The really interesting finding, however, is that the neurons allowing the Alzheimer’s mice to remember their environment were still being activated and were functioning. However, the memory couldn't be retrieved because the signal was blocked by other neurons that encoded the environment as a new experience. Such interfering or blocking effects are called “noise.” Leader of the research group, Dr. Martin Fuhrmann, explains, "It is like a noisy TV signal: the picture becomes diffuse and distorted; you might even see pixels or stripes. Something similar happened inside the mice's brain: Interfering signals suppressed their memories. This disturbance is obviously a result of the pathological changes in the brain." The study begs the question, would removing the noise restore the memory? The scientists took a closer look.

Switching Memories “On” or “Off”

There’s a scientific technique that combines alterations to chemical molecules and genes called chemogenetics. The scientists used this technique to adjust the activity of neurons in both groups of mice so that researchers could switch the neurons that encode new experiences to “on” or “off.” First, they switched the neurons “on” in the healthy mice to create noise. As a result, the mice’s memory for the environment they’d previously explored was impaired. Then, when they switched neurons “off” in the Alzheimer's mice, the noise disappeared. Now they were able to recognize and remember the environment they’d experienced several days earlier. "The results of this study indicate a previously unknown mechanism that may contribute to the memory impairment in Alzheimer's disease,” explains Dr. Fuhrmann. "Imagining future therapies, we might be able to rescue memories of individuals suffering from Alzheimer's disease or other diseases impacting memory recall. We might achieve this by lowering the activity of these noise-inducing neurons with future methods." He also believes the technique has application to people suffering post-traumatic stress disorder. In this case, noise-inducing neurons could be switched on to overwrite the traumatic memory.
  1. https://www.dzne.de/en/news/press-releases/press/alzheimer-research-noise-inducing-neurons-shut-down-memories

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