achieved in mice implanted false memories - CNN

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Image of a laboratory mouse rise to Mrmin123 on Flickr Flickr

Madrid. (Europa Press). – In a step toward understanding how faulty memories arise, neuroscientists at the Massachusetts Institute of Technology (MIT , its acronym in English) in the United States, have shown that can planting false memories in the brains of mice . They also found that many of the neurological signs of these memories are identical in nature to those of authentic memorabilia.

“Whether it is true or false memory, the brain’s neural mechanism underlying the memory retrieval is the same,” says Susumu Tonegawa, a professor of biology and neuroscience at MIT Picower Institute and lead author of paper describing the findings in Thursday’s issue of Science .

The study provides further evidence that memories are stored in networks of neurons forming memory traces of every experience we have, a phenomenon that Tonegawa’s laboratory showed last year. Neuroscientists have long sought the location of these memory traces, also called engrams.

his pair of studies, Tonegawa and colleagues at the Picower Institute for Learning and Memory showed that they could identify cells that are part of a specific memory engram and reactivate using a technology called optogenetics.

Episodic memories are the result of associations of various elements, objects, space and time. These associations are encoded by chemical and physical changes in neurons, as well as changes in the connections between neurons. How long these engrams reside in the brain has been a long question in neuroscience.

“Is the information in several parts of the brain or is there a particular area of ??the brain that stores this type of memory? This has been a very fundamental question,” poses Tonegawa. In the 1940s, Canadian neurosurgeon Wilder Penfield suggested that episodic memories are located in the temporal lobe of the brain, because when electrically stimulated cells in the temporal lobes of patients who were about to undergo surgery to treat epileptic seizures, patients reported that specific memories came to mind them.

Subsequent studies

amnesic patient known as HM confirmed that the temporal lobe, including the area known as the hippocampus is critical for episodic memory formation. However, these studies do not prove that engrams are actually stored in the hippocampus, highlights Tonegawa.

Scientists needed

demonstrate that activation of specific groups of cells in the hippocampus are sufficient to produce and retrieve memories, for which the Tonegawa laboratory used optogenetics, a new technology that enables or desacatirs selectively cells using light. For this pair of studies, the researchers engineered mice hippocampal cells expressing channelrhodopsin gene, a protein that activates neurons when stimulated by light, in addition to modifying the channelrhodopsin gene so that always occur with the c Delphi, necessary for memory formation.

last year’s study, the researchers conditioned these mice to fear a particular camera by delivering mild electric shock. As this memory is formed, the c-fos gene was activated along with the channelrhodopsin gene engineering. In this way, cells which encode the memory footprint is “tagged” with the light sensitive proteins. The next day, when the mice were put on a different camera that had never seen before, behaved normally, but when the researchers sent a pulse of light in the hippocampus, stimulating memory cells labeled with channelrhodopsin, mice were prey of fear when reactivated his memory of the previous day.

“Compared with most studies treating the brain as a black box when trying to access it from the outside, we are trying to study the brain from the inside out – concrete Liu -. The technology we developed for this study allows us to dissect and even potentially intervene in the process of memory through direct control of brain cells. ” That’s exactly what they did the researchers in the new study: to explore if they could use these engrams reactivated to plant false memories in the brains of mice.

First, put the mice into a new camera, A, but without any discharge, and when the scanned rodents, their memory cells labeled with Channelrhodopsin. the next day, mice were placed in a second chamber positioned very different, B, and after a while, they were given a mild shock to the foot and at the same instant, the researchers used light to activate cells encoding camera memory A. On the third day, mice were placed back into the chamber A, where now were paralyzed, although they had never been subjected to a shock there. ” He acted a false memory: mice fear Room A by memory, because when given a discharge in chamber B, were reliving the memory of when they were in the chamber A.

Moreover, the false memory seemed to compete with a real camera memory B, the researchers found. These mice also froze when placed in chamber B, but not as much as the mice that had received a shock in the camera without the camera B A in active memory. The researchers then showed that immediately after the withdrawal of false memories, levels of nerve activity were also elevated in the amygdala, the fear center in the brain that receives information from the memory of the hippocampus, as it when mice are reminiscent of a memory genuine.