To determine where fear-related memories originate in the brain, Dr. Steven Siegelbaum’s lab at Columbia University’s Zuckerman Institute used a powerful technique to conduct a series of tests on mice.
During the study, scientists examined the hippocampus, an area of the brain that plays a major role in memory in humans and mice. In particular, they focused on the CA2 area, which is important for social memory, the ability to remember other people, and the CA1 area, which is important for remembering places.
The team discovered for the first time that CA1 and CA2 respectively encode locations and individuals associated with a threatening experience.
The results show that beyond recognizing individuals, the CA2 area helps record more complex aspects of social memory: in this case, whether another individual is safe or risky.
“It is essential for all species that live in social circles, including mice and humans, to have social memories that help them avoid future experiences,” said Pegah Kasrayan, Ph.D., a postdoctoral research fellow in Siegelbaum’s lab and lead author of the new study. with others that may prove harmful while maintaining our openness to individuals who may be helpful. “Frightening memories are important for survival and help keep us safe.”
To investigate where fearful social memories originate in the brain, Dr. Kasrayan and her colleagues gave individual mice the option of running somewhere, meeting another mouse unknown to them, and receiving a mild shock to the foot (like the static electricity shock people might experience after walking on a carpet and touching a handle). door). It was safe to run in the opposite direction to meet a different stranger.
The mice quickly learned to avoid strangers and places associated with the trauma, and these memories lasted for at least 24 hours.
To determine where these memories are stored in the hippocampus, the team genetically modified mice to enable them to selectively suppress CA1 or CA2 areas. Surprisingly, turning off each zone had very different effects.
When the scientists silenced CA1, the mice could no longer remember where they had been shocked, but they still remembered which stranger was associated with the threat. When they silenced CA2, the mice remembered the place where they had been shocked, but became randomly afraid of the strangers they met.
These new findings reveal that the CA2 area helps mice remember whether previous encounters with others were threatening or safe. The findings are also consistent with previous research detailing how CA1 is home to place cells, which encode locations.
Previous research has implicated CA2 in several neuropsychiatric conditions such as schizophrenia and autism. According to the new study, further investigation into CA2 may help better understand social anxiety, post-traumatic stress disorder, and other conditions that may lead to social withdrawal.
The findings were detailed on October 15 in the journal Nature Neuroscience.
Source: Medical Express
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