Scientists have discovered that a surprising type of brain cell—not the ones most people have heard of—plays a key role in keeping emotional memories alive. For decades, researchers believed that neurons, the cells that send signals in the brain, were solely responsible for storing memories. But a new study published in Nature has revealed that another cell type, called the astrocyte, helps lock in emotional experiences so we can remember them later.
Astrocytes were long thought to be the brain’s support crew—cells that simply feed and protect neurons. But the new research shows they are much more active and important than previously believed. The big discovery came from a memory experiment involving mice.
In the study, mice were placed in a cage where they received a mild shock to their feet. During this first experience, the astrocytes stayed quiet, and only neurons showed signs of activity. Days later, the same mice were placed in the cage again. Even though they were not shocked the second time, they remembered the fear. This time, the astrocytes lit up with activity, especially in parts of the brain linked to emotion, such as the amygdala.
This surprised scientists. They had expected astrocytes, if they played any role at all, to be involved during the original memory formation. Instead, the cells only became active when the emotional memory was recalled or repeated. The researchers believe this shows that astrocytes help stabilize and “save” memories after the brain decides they are important enough to keep.
The study also revealed how this process happens. After repeated exposure to emotional experiences, astrocytes begin producing more receptors for a chemical called noradrenaline, which the body releases during stress and strong emotions. These receptors seem to act like tags, marking which astrocytes were involved in the experience and helping them communicate with neurons to hold onto the memory long-term. This tagging process takes hours to days, which matches how emotional events gradually turn into lasting memories.
Experts say the findings could change how scientists think about memory altogether. One neuroscientist who was not part of the research called it “revolutionary,” saying it may shift the field away from a neuron-only view and toward a model where astrocytes are active partners in shaping what we remember.
The discovery could also open new possibilities for treating memory-related conditions. If astrocytes help strengthen emotional memories, targeting them might lead to better treatments for disorders such as PTSD, where painful memories persist, or Alzheimer’s disease, where memory fades.
The research was led by Jun Nagai at the RIKEN Center for Brain Science in Japan and published on October 15, 2025. As scientists continue to uncover the hidden roles of astrocytes, our understanding of how the brain remembers may be entering a new era.
