Brain Stars Function as Tiny Storage Units for Our Memories

Recent research into how “brain stars” (astrocytes) store memories has reshaped our understanding of memory retention in the brain.

Previous Beliefs About Memory and Neurons

Scientists at Baylor College of Medicine have been examining the role of astrocytes, star-shaped cells in the brain that function as tiny storage units for memories. These cells work in tandem with specific neurons called engrams, which regulate and retrieve memories when needed.

Previous beliefs held that only neuronal networks were responsible for learning and memory. The prevailing theory stated that neuronal engrams, activated by particular experiences, solely managed memory formation and recall, serving to store and retrieve memories.

However, Dr. Benjamin Deneen, a professor at Baylor and principal investigator at the Jan and Dan Duncan Neurological Research Institute, notes that his team’s research challenges this assumption. “While we have long studied astrocytes and their interactions with neurons, the role of astrocytes in memory storage and retrieval was unexplored until now,” he explains.

The Brain’s Enigmatic Nature

Despite the significant progress in understanding the brain’s mechanisms, it remains one of the most enigmatic organs in the body. In 2016, Stanford researchers highlighted the considerable hurdles that neuroscientists face, and although they have made advancements in areas like neurological conditions, much remains unknown.

To investigate, Baylor’s team used a mouse model to examine astrocytes’ role in memory. They conditioned the mice to associate a fearful event with a particular environment. When placed in a similar situation later, the mice froze, showing a fear response. However, when placed in a completely different context, they did not react in the same way.

The researchers discovered that the fear-induced learning process triggered a subset of astrocytes expressing the c-Fos gene, which plays a crucial role in the brain’s circuitry. “These c-Fos-expressing astrocytes are physically close to engram neurons,” said Michael R. Williamson, co-first author of the study. “Additionally, we found that the engram neurons and astrocytes are functionally connected. Activating the astrocytes stimulates synaptic communication in the corresponding engram neurons.”

Astrocyte Activation and Memory Recall

The team further observed that activating the astrocytes in a fear-associated environment triggered the freezing response in the mice. However, when the researchers activated the same astrocytes in a non-fearful setting, the mice still froze, demonstrating that astrocyte activation involves memory recall.

The researchers also revisited their previous findings regarding the gene NFIA, which plays a key role in regulating astrocyte memory circuits. They discovered that suppressing NFIA levels in active astrocytes impaired memory retrieval.

“When we deleted the NFIA gene in active astrocytes, the mice could not recall the specific memory associated with a prior learning event, though they could remember other experiences,” said co-first author Wookbong Kwon.

This discovery significantly impacts conditions like Alzheimer’s disease, where memory retrieval is compromised, and PTSD, where certain memories can be harmful.

Deneen concluded, “These findings highlight the specific role of astrocytes in memory. Different ensembles of astrocytes regulate the recall of distinct learning events. The ensembles associated with fear-based memories differ from those related to other experiences, and the same holds true for the neurons involved.”

Future Applications of Memory Research

As research into the brain continues, future therapies may offer more targeted treatments for memory issues, potentially moving beyond the fictional approaches seen in films like Eternal Sunshine of the Spotless Mind.

Read the original article on: New Atlas

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