Why is it that we tend to remember emotional events quite vividly? A study recently published in Nature reveals that a type of brain cell known as an astrocyte plays a significant role in stabilizing long-term memories.
Initially, astrocytes were thought to merely support neurons in creating memory traces, but this new research suggests they have a more active involvement. Interestingly, they can be directly activated by repeated emotional experiences, opening up potential new avenues for treating memory disorders associated with conditions like post-traumatic stress disorder and Alzheimer’s disease.
“We provide an answer to the question of how a specific memory is stored for the long term,” shares Jun Nagai, a neuroscientist at RIKEN Center for Brain Science in Wako, Japan. The study highlights how astrocytes help the brain selectively process important memories at a cellular level.
Understanding Memory Stabilization
Nagai and his team delved into the stabilization of memories—specifically, how short-term memories transition into something more permanent. Previous research had identified physical traces of memories in brain areas like the hippocampus and amygdala, but the mechanism behind storing these lasting memories after repeated exposure to the same experience was still unclear.
To investigate further, the researchers developed a method to measure activation patterns in astrocytes throughout a mouse brain while the animal completed a memory task. They focused on a gene called Fos, an early marker of cell activity linked to the physical traces of memories.
In a commonly used fear conditioning memory task, mice learned to associate a specific cage with unpleasant foot shocks. During this process, the researchers monitored levels of Fos in the mice’s brains. When the animals returned to the cage days later, they remembered the unpleasant shocks. Notably, there was significant Fos upregulation in the astrocytes of their amygdalas and other brain regions during this recall, but not when they were initially learning, indicating that astrocyte activity is more crucial for recalling past events than for forming new memories.
“What surprised us was that astrocytes didn’t respond to the fear experience during the first encounter, only on the second,” says Nagai.
