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Memory problems linked to faulty receptor in brain

Teresa Tanoos's picture
Researchers say memory problems due to faulty receptor in brain.

If you’re having problems remembering things lately, it may be due to a faulty receptor in your brain, according to a study published in the journal PLOS One.

Researchers from the Medical College of Georgia conducted the study using mice and found when they deactivated a primary switch in the brain associated with memory and learning, the reactions of the mice indicated they had forgotten what they had previously learned from a series of conditioning exercises that used sounds and mild foot shocks to create associations through repetition.

As a result, the researchers believe they are on the path to cracking the code as it pertains to figuring out how thoughts and memories are produced in real time – and this, they say, could help in determining what contributes to memory loss as people age, therefore leading to new treatments that slow down the process of losing memory over time.

The study analyzed mice that lacked N-methyl-D-aspartate (NMDA), a receptor that controls learning and memory, as well as the connections between synapses and whether they are strengthened or weakened over time. The NMDA receptor is located in the hippocampus of the brain, where the formation and organization of memories is stored.

For the study, which used a conditioning model to illustrate the link between repetition and association, researchers conducted experiments on the mice using sounds associated with negative behaviors to see how the mice reacted. When a certain sound was played for the mice, they received a mild shock after 20 seconds.

Next, the reactions of the mice were compared between those with normal NMDA receptors and those with an abnormally functioning NMDA receptor.

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What the researchers found was that the mice with faulty NMDA receptors ended up with memory problems as evidenced by how they struggled to “remember” the association between the specific sound and the mild shock that they had previously been conditioned to learn.

On the other hand, those mice that had a healthy NMDA receptor reacted normally, remembering quickly the association between the sound and shock they’d previously been conditioned to make.

However, when the researchers deactivated the NMDA receptor, the mice with a normally functioning receptor reacted like the mice with faulty receptors, demonstrating a failure to remember the shock that came after hearing a certain sound.

Dr. Joe Tsien, a neuroscientist at the Medical College of Georgia, explained that it’s similar to when you see someone’s face and think of a name, or when you go to the office and think of work you have to do.

In this regard, Dr. Tsien says that “everything is associative", but in the mice with the faulty NMDA receptor, he added that it becomes clear that their memories are “dull and dissociated."

Dr. Tsien says that the findings of the study could lead to new and improved treatments for memory loss due to aging, as well as for Alzheimer's disease and schizophrenia.

By looking for memory patterns and what they mean, he says that these could be used as a measure for how much memory has been lost, while helping determine what drugs or other treatments might be effective for improving memory.

SOURCE: Mapping and Deciphering Neural Codes of NMDA Receptor-Dependent Fear Memory Engrams in the Hippocampus, DOI: 10.1371/journal.pone.0079454, Hongmiao Zhang, Guifen Chen, Hui Kuang, Joe Z. Tsien, published in PLOS One, 26 November 2013.