Smell and emotion create lasting memories. Even in a sleeping person.

In a series of experiments on sleeping mice, scientists at Duke University Medical Center have shown that the part of the brain that processes smells is indeed key to forming long-term memories, especially those involving other people. Marcel Proust was right. When he dipped the biscuit into tea, the unmistakable aroma that wafted through the air opened a gateway to the writer's memory. Perhaps each of us can recall a moment when we entered a room and smelled something that evoked vivid and emotional memories of a family member we hadn't seen for years. Researchers at Duke University have analyzed this phenomenon at the cellular level. How is memory of smells created? A team from the university administered anesthesia to mice. Norepinephrine release was triggered by an electrode and the smell of food or another rodent's urine. The researchers essentially recreated the chemical reaction that would accompany a mouse during labor. After inducing norepinephrine activity, they observed an average 40% reduction in neuronal activity. This indicates that a memory of the odor had formed at that moment. The next day, while the rodents were awake, they observed behavioral changes in response to the odors. This is evidence that the mice remembered the odors sprayed during their sleep. Studying memory at the cellular level American scientists investigated how powerful memories are formed by generating new memories in the minds of sedated mice. The researchers monitored their responses to memory-eliciting stimuli while the rodents were awake. The researchers' approach allowed them to analyze the cellular makeup of memory, assess how neurons change as memories form, and understand how memory influences behavior. The role of noradrenaline By stimulating the production of norepinephrine, a chemical present in the body during strong emotional states such as excitement and fear, memories were created in mice. In both mice and humans, the presence of norepinephrine triggers changes in the brain's odor-processing center, the olfactory bulb. Noradrenaline and Smell are Keys to Creating a Memory For an animal to form a strong memory of another animal, the presence of an odor and norepinephrine are necessary. Both stimuli must occur at the same time. Long-lasting memories formed under these conditions often result in lasting behavioral changes. Why did they study mice under anesthesia? During sleep, brain activity is easier to study in greater detail. If a mouse were conscious, it could form memories from its surroundings. This way, when it awoke, it was possible to learn what the rodent had learned during its sleep.