. This discovery came from experiments on mice. When long-term memories are formed, some brain cells experience extremely strong electrical activity, so strong that it can cause breaks in DNA. Subsequently, an inflammatory response is triggered to repair this damage, helping to consolidate memories.
I found some related comments quite amusing:
Now I understand why I couldn't memorize things when studying; turns out my genes were too strong. My brain is self-protecting and doesn't want me to learn.
, leading to the accumulation of errors in neuronal DNA.
For the first time linking DNA damage to memory, in 2021, Li-Huei Tsai, a neurobiologist at MIT in Cambridge, and her colleagues found that double-strand DNA breaks are common in the brain and linked them to the learning process.
To better understand the role of DNA breaks in memory formation, Radulovic and her team trained mice to associate mild electric shocks with a new environment. When placed back in that environment, the mice showed signs of "remembering" the experience, such as freezing in place and displaying fear. The researchers then analyzed gene activity in neurons within the hippocampus, a brain region closely associated with memory formation. They found that four days after training, a group of neurons showed higher activity in inflammation-related genes. However, three weeks after training, the activity of these genes had significantly decreased.
TLR9. TLR9 triggers an immune response to free-floating DNA fragments inside cells. Radulovic explained that this inflammatory response is similar to how immune cells defend against invading pathogens' genetic material. However, the study found that, in this case, nerve cells were not responding to external invaders but rather reacting to their own DNA.
The study revealed that TLR9 was most active in a small subset of neurons in the hippocampus, where DNA breaks were harder to repair. In these cells, DNA repair mechanisms gathered around an organelle called the centrosome, which is typically associated with cell division and differentiation. However, mature neurons do not divide, so Radulovic pointed out that the involvement of the centrosome in DNA repair was unexpected. She speculated that the mechanism of memory formation might resemble the adaptive process of immune cells when they encounter foreign substances. That is, during cycles of damage and repair, neurons may encode information about memory-forming events that trigger DNA breaks.
When researchers deleted the gene encoding the TLR9 protein in mice, these mice experienced difficulties in recalling long-term memories: when placed back in the environment where they had previously received shocks, they exhibited significantly less freezing behavior compared to mice with intact genes. Radulovic stated that these findings indicate
So can long-term memory be inherited?