Discovery of neurons that recognize others

The hippocampus plays an important role in assigning positive values to others.

Share

Researchers at the Institute for Basic Science’s Center for Cognition and Sociality (CCS) recently revealed the finding of neurons that allow us to recognize others.

The research team identified the neurons that deal with information linked with various persons to be located in the CA1 area of the hippocampus. 

Humans and other social creatures are continuously interacting with others. The ability to detect the identity of the social counterpart, extract essential information about them from memory, and update it from the current contact is critical for establishing social bonds. However, research on how these mechanisms occur in the brain has yet to be restricted.

Most previous attempts to address this subject concentrated on mouse brain research, notably in the hippocampus. Since the hippocampus is a well-known brain structure in memory formation, it was assumed to be the solution. The Cornu Ammonis (CA) fields, located in the hippocampus and designated by the letters CA1, CA2, and CA3, are important for various memory and spatial processing processes.

The CA2 area of the hippocampus has been the primary focus of mice investigations on the neurological basis of individual recognition thus far. However, earlier experiments only involved separating unfamiliar from known mice in behavioral assays, making it challenging to determine whether the outcomes reflect the animal’s capacity for perception.

In this new study, the IBS-CCS research group created a novel behavioral paradigm in mice to examine their capacity for social recognition more thoroughly.

They tested the behavior of the subject mouse after encountering reward-associated and non-associated mice using their innovative method, which involves having the subject mouse associate particular individual mice with incentives.

In particular, two mice were immobilized on a rotating disk. They were given in a random order to a subject mouse, which would scent the neighbor.

The subject mouse is then given water from the device as a reward when it licks in reaction to the reward-associated mouse but not another. 

During the experiment, the scientists monitored the activity of the subject mouse’s brain cells to see if it could discriminate against various people.

The stimulus mice on the spinning disk were male littermates, and the subject mice were already familiar with the stimulus mice. 

This indicates the great dependability of the experimental findings since the subject mice differentiated from the stimuli mice purely based on the distinctive traits of the stimulus mice.

The IBS-CCS team has shown the dorsal CA1 area of the hippocampus to be crucial for individual recognition. The team’s two-photon imaging method allowed them to pinpoint the precise neuronal cells in the hippocampal CA1 area that distinguish individual mice.

The dorsal CA2 region of the hippocampus is suggested to be the critical brain region for social memory in prior research, which also indicated that the dorsal CA1 region does not significantly contribute to social memory. This is an intriguing addition to those findings.

Additionally, previous studies suggested that rodents do not build long-term memories for specific subjects and that their social memories are temporary. 

However, the newest IBS-CCS study has shown that mice can develop long-term memories of specific people.

“We have revealed for the first time how to value information about others obtained through positive or negative interactions with them is represented and stored in our brains.” said Dr. LEE Doyun, the study’s principal investigator.

 Additionally, this offers important insights into comprehending how our brains contribute to the growth and development of human relationships through diverse social encounters.

Additionally, it demonstrated the existence of specific neurons that process positive stimuli in the subject mouse’s hippocampal CA1 area.

These specific CA1 neurons were found to be responsive when encountering reward-associated individuals. However, such reward expectation responses were not observed when the subject was exposed to odors unrelated to social activity, such as citral or butanol.

These findings indicate that the hippocampal CA1 region is selectively important in forming associative social memories. This new discovery can lead to a potential solution for treating various brain disorders that cause difficulty developing social relationships.

Dr. Lee. said, “Our results could be utilized to understand and propose treatment methods for mental disorders such as autism, which exhibit abnormalities in brain functions involved in processing memories and related information about others.” 

Journal Reference:

  1. Kong, E., Lee, K., Do,et al. Dynamic and stable hippocampal representations of social identity and reward expectation support associative social memory in male mice. Nature Communications. DOI: 10.1038/s41467-023-38338-3

Newsletter

See stories of the future in your inbox each morning.

Trending