Summary: Researchers have uncovered a surprising role for astrocytes—cells surrounding neurons—in deciding which memories are kept or forgotten.
By manipulating astrocytes in mice using optogenetics, scientists found that acidifying these cells after a traumatic experience leads to forgetting the memory over time, while alkalinizing them preserves it long-term. This suggests astrocytes significantly influence emotional memory retention and could inform treatments for conditions like PTSD.
Unlike previous theories, these findings imply that short- and long-term memories may form in parallel, rather than sequentially. Further exploration into astrocyte roles may reveal new approaches for managing emotional memory.
Key Facts:
- Acidifying astrocytes in mice’s brains resulted in lost fear memories over time.
- Alkalinizing astrocytes preserved traumatic memories even three weeks post-exposure.
- Astrocytes may play a key role in emotional memory formation and PTSD treatment.
Source: Tohoku University
One of the most powerful assets of the brain is that it can store information as memories, allowing us to learn from our mistakes.
However, some memories remain vivid, while others become forgotten. Unlike computers, our brains appear to filter which memories are salient enough to store.
Researchers from Tohoku University discovered that part of the memory selection process depends on the function of astrocytes, a special type of cell that surrounds neurons in the brain.
They showed that artificially acidifying the astrocytes did not affect short-term memory but prevented memories from being remembered long-term.
The findings were detailed in the journal GLIA on November 4, 2024.
The researchers implemented a technique called “optogenetics” to manipulate the astrocytes by shining light onto them through optical fibers inserted in the mice’s brains.
This enabled researchers to directly stimulate and either acidify or alkalinize the astrocytes in that area. They focused on the functions of astrocytes in the amygdala, a brain region known to be crucial for regulating emotion and fear.
A mild electrical shock was delivered to mice in an experiment chamber. When placed back in the same chamber, the mice remembered the shock and froze as a natural response.
In comparison, the mice who had their astrocytes acidified immediately after the mild shock were able to temporarily hold onto the fear memory, but they forgot it by the next day. This shows that acidifying the astrocytes did not affect short-term memory but prevented the memories from being remembered long-term.
A different effect was seen for mice who had their astrocytes alkalinized. When tested three weeks later, control mice typically showed signs of forgetting, demonstrated by a decrease in freezing responses.
However, mice whose astrocytes were alkalinized immediately after a strong shock still displayed strong fear responses even after three weeks. This suggests that astrocytes play a key role in determining whether memories are erased or preserved for a long time, immediately after a traumatic event.
While it is generally believed that memories are formed in a continuous process whereby short-term memories gradually solidify and become long-term memories, this research suggests they may actually develop in parallel.
“We believe that this could change the way we understand memory formation,” says Professor Ko Matsui of the Super-network Brain Physiology lab at Tohoku University, who led the research.
He added, “The effect of astrocytes on memory likely also depends on various contexts, including mental, social, or environmental factors.”
Lead investigator Hiroki Yamao believes astrocytes could hold the key to understanding emotional changes and memory formation.
“This may be just a glimpse of how astrocytes affect emotional information processing,” Yamao explains.
“Our next goal is to uncover the mechanisms by which astrocytes regulate emotional memory. Understanding these processes could pave the way for therapies that prevent traumatic memories from forming, offering a valuable approach to treating disorders like post-traumatic stress disorder (PTSD) by intervening in memory formation.”
About this neuroscience and memory research news
Author: Public Relations
Source: Tohoku University
Contact: Public Relations – Tohoku University
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Astrocytic determinant of the fate of long-term memory” by Ko Matsui et al. Glia
Abstract
Astrocytic determinant of the fate of long-term memory
While some vivid memories are unyielding and unforgettable, others fade with time. Astrocytes are recognized for their role in modulating the brain’s environment and have recently been considered integral to the brain’s information processing and memory formation. This suggests their potential roles in emotional perception and memory formation.
In this study, we delve into the impact of amygdala astrocytes on fear behaviors and memory, employing astrocyte-specific optogenetic manipulations in mice.
Our findings reveal that astrocytic photoactivation with channelrhodopsin-2 (ChR2) provokes aversive behavioral responses, while archaerhodopsin-T (ArchT) photoactivation diminishes fear perception. ChR2 photoactivation amplifies fear perception and fear memory encoding but obstructs its consolidation.
On the other hand, ArchT photoactivation inhibits memory formation during intense aversive stimuli, possibly due to weakened fear perception. However, it prevents the decay of remote fear memory over three weeks.
Crucially, these memory effects were observed when optogenetic manipulations coincided with the aversive experience, indicating a deterministic role of astrocytic states at the exact moment of fear experiences in shaping long-term memory.
This research underscores the significant and multifaceted role of astrocytes in emotional perception, fear memory formation, and modulation, suggesting a sophisticated astrocyte-neuron communication mechanism underlying basic emotional state transitions of information processing in the brain.
