| ▲ Loss of ability to discriminate between objects when the CA1 area of the hippocampus is blocked (Photo = Provided by the Foundation for Basic Science) |
[메디컬투데이=이재혁 기자] Social animals, including humans, constantly interact with other individuals. In the process of interaction, it recognizes different entities and retrieves from memory information related to those entities accumulated from previous interactions. And it adds and integrates new information, and this ability is fundamental to establishing social relationships. However, it is not clear how this process takes place in the brain.
Research Fellow Lee Do-yoon’s research team at the Center for Cognition and Sociality at the Institute of Basic Science (IBS) under the Ministry of Science and ICT used mouse behavioral experiments and cranial nerve imaging technology to identify object recognition neurons that are activated when the other person will be recognized and associated with the recognized object On the 1st, it was revealed that the nerve cells that process value information exist in the CA1 region of the hippocampus.
For this study, the research team devised a new behavioral experimental device that allows mice to discriminate between individuals. One of the two mice immobilized on a spinning disc is presented to the test mice in random order. Water is delivered from the device to the test mouse as a reward when one particular mouse is presented, but not when another mouse is presented. It’s called the ‘Go-NoGo experiment’. Through this experiment, the research team confirmed whether the mice could distinguish between objects, and analyzed the activity of the nerve cells in the mice’s brain during the experiment.
As a result, it was found that mice can distinguish between individuals by smelling each other for a short time, and this is possible because of the upper CA1 region of the hippocampus. When the research team injected a neuro-inhibitory substance into the CA1 region of the hippocampus and inhibited that region, the experimental mice could not differentiate between the introduced mice. In addition, by using two-photon microscopy, which can observe the activity of nerve cells in the deep brain in real time, it was identified that nerve cells that differentiate and recognize different mice are located in the CA1 area.
Furthermore, the researchers found that information-processing neurons that value information related to individual entities are also present in the CA1 region of the hippocampus. It is important to form social relationships to link an individual’s subjective evaluation of social experience with information about the value (positive, negative, etc.) of a particular individual, and to update that value. For example, just as it is essential to develop a friendship with a particular individual, it is essential to evaluate how enjoyable and rewarding it was to interact with them.
However, the activation of nerve cells that process this value information was not observed in behavioral experiments involving odors (citral and butanol) that had nothing to do with mice. When the brain associates information with different stimuli, the CA1 region of the hippocampus associates appreciates information only when the stimulus is a mouse. This means that the CA1 region of the hippocampus acts selectively in the formation of social association memories.
Previous studies on the neural mechanism of object recognition using mice mainly focused on the upper CA2 and lower CA1 regions of the hippocampus, but in this study, the upper CA1 region was found to play an important role. In addition, existing studies to distinguish between unfamiliar and familiar mice were only behavioral experiments, and there was a limitation because the results of the experiments could not be clearly interpreted as recognizing the unique characteristics of the actual object.
However, the mice used in this experiment were male siblings, of the same sex, age, and genetic makeup, and were familiar with the test mice. This means that the mice are distinguished only by the unique characteristics of the objects, suggesting a high reliability of the experimental results.
Research Fellow Lee Do-yoon said, “For the first time, we have identified how value information about individuals obtained through positive or negative interactions is expressed and stored in our brain. What role does our brain play in forming human relationships through various social interactions It is meaningful as it has laid the foundation for understanding whether we do it or not.”
In addition, he said, “This study can be used to understand mental diseases such as autism, which show abnormalities in brain function that processes memory and related information about others, and to suggest treatment methods.”
Meanwhile, the results of this research were published online on May 5 in Nature Communications (IF: 17.694), a sister journal of Nature.
Correspondent Lee Jae-hyeok of Medical Today (dlwogur93@mdtoday.co.kr)
[저작권자ⓒ 메디컬투데이. 무단전재-재배포 금지]
