Where does the brain keep pleasant memories?

By Casey Frye, CCNN Writer

Researchers from the Nencki Institute in Warsaw find where pleasant memories are stored in the brain using mice and an intelligent cage.

I want you to think about eating your most favorite meal in the whole world. Mmmmm… just the thought leaves your mouth watering, doesn’t it? Okay, now pretend being forced to chew on something you absolutely hate. Yuck! Even though it’s not actually there in your mouth, your nose crinkles in disgust, huh?

Well, part of the reason we react to these thoughts so strongly is because we have both pleasant and unpleasant memories locked up in our brains. It’s not only humans either, because animals also have a similar distinction between the two stored somewhere in their heads. Exactly where had always been a mystery, until researchers from the Nencki Institute in Warsaw discovered where the good ones are stored for safekeeping!

In order to pinpoint where the pleasant memories were, the researchers ingeniously used mice and put them in a cage known as the IntelliCage. This mouse home is special because in each corner there are two bottles for the tiny critters. In this particular experiment, one of the bottles was filled with sweet water, while the other gave an unpleasant puff of air straight to the face. Also, the researchers used two types of mice. One of them had perfectly functioning parts. However, the others lacked a protein called MMP-9, which the researchers suspected played a role in pleasant memories.

Well, their guess was right, because there was a huge difference between the mice when they were placed in the cages. Once the normal ones could tell the differences between the bottles that had sweet water and puffed air, the always chose the drink. Meanwhile, the animals lacking  MMP-9 had no preference about which bottle they chose. Now, that’s not to say they couldn’t remember which was which, as researchers point out, but it’s like the second type of mice didn’t remember that they didn’t like the blast of air!

With these results, the researchers found that pleasant memories are stored in a part of the brain known as the amygdala, which is responsible for emotional responses like fear and laughter. “We want our research to help us understand the relation between the mind and the brain by studying memory, which is of fundamental importance for the mind,” said professor Leszek Kaczmarek, who was involved in the study. “Without memory there is no mind.”

Featured image courtesy of Achim Schrepfer on Flickr. Image of intelligent cage courtesy of Nencki Institute and Grzegorz Krzyżewski.