When we go to a friend or go to the beach, our mind shops a short-term memory of the experience in a part of the mind called the hippocampus. These reminiscences are later "consolidated" - that is, transferred to another a part of the brain for longer-term storage. A new MIT research of the neural circuits that underlie this process reveals, for the primary time, that recollections are actually formed simultaneously within the hippocampus and the lengthy-time period storage location in the brain’s cortex. However, the long-term recollections stay "silent" for about two weeks before reaching a mature state. "This and other findings in this paper provide a complete circuit mechanism for consolidation of memory," says Susumu Tonegawa, the Picower Professor of Biology and Neuroscience, the director of the RIKEN-MIT Center for Neural Circuit Genetics at the Picower Institute for Learning and Memory, and the study’s senior writer. The findings, which seem in Science on April 6, could drive some revision of the dominant models of how memory consolidation happens, the researchers say.

The paper’s lead authors are analysis scientist Takashi Kitamura, postdoc Sachie Ogawa, and graduate scholar Dheeraj Roy. Other authors are postdocs Teruhiro Okuyama and Mark Morrissey, technical affiliate Lillian Smith, and former postdoc Roger Redondo. Starting within the 1950s, research of the famous amnesiac patient Henry Molaison, then identified solely as Patient H.M., revealed that the hippocampus is essential for forming new long-term memories. Molaison, whose hippocampus was damaged during an operation meant to help control his epileptic seizures, was not capable of store new reminiscences after the operation. Nonetheless, he might nonetheless access some reminiscences that had been formed earlier than the surgery. This instructed that long-term episodic recollections (memories of particular events) are saved outdoors the hippocampus. Scientists consider these reminiscences are saved in the neocortex, the a part of the mind additionally answerable for cognitive capabilities equivalent to attention and planning. Neuroscientists have developed two main models to describe how memories are transferred from brief- to lengthy-time period memory.

The earliest, referred to as the standard mannequin, proposes that quick-term reminiscences are initially formed and stored within the hippocampus solely, Memory Wave earlier than being regularly transferred to long-term storage within the neocortex and disappearing from the hippocampus. A newer mannequin, the a number of trace model, suggests that traces of episodic reminiscences remain within the hippocampus. These traces might store details of the memory, while the more basic outlines are saved within the neocortex. Till not too long ago, there was no good way to check these theories. Most previous research of memory have been based mostly on analyzing how injury to certain brain areas impacts memories. Nevertheless, in 2012, Tonegawa’s lab developed a solution to label cells referred to as engram cells, which contain particular recollections. This enables the researchers to hint the circuits involved in Memory Wave Experience storage and retrieval. They can even artificially reactivate reminiscences by using optogenetics, a method that allows them to show target cells on or off utilizing gentle. In the brand new Science examine, the researchers used this approach to label memory cells in mice during a fear-conditioning event - that is, a mild electric shock delivered when the mouse is in a specific chamber.

Then, they might use mild to artificially reactivate these memory cells at different times and see if that reactivation provoked a behavioral response from the mice (freezing in place). The researchers might also decide which memory cells had been energetic when the mice have been placed within the chamber where the fear conditioning occurred, prompting them to naturally recall the memory. The researchers labeled memory cells in three parts of the mind: the hippocampus, the prefrontal cortex, and the basolateral amygdala, which shops memories’ emotional associations. Just in the future after the worry-conditioning occasion, the researchers found that recollections of the occasion were being saved in engram cells in both the hippocampus and the prefrontal cortex. Nevertheless, the engram cells within the prefrontal cortex have been "silent" - they could stimulate freezing behavior when artificially activated by gentle, but they didn't fire during pure memory recall. "Already the prefrontal cortex contained the specific memory information," Kitamura says. "This is opposite to the standard idea of memory consolidation, which says that you steadily transfer the recollections.

Edit

Pub: 29 Aug 2025 20:04 UTC

Views: 16