How does an animal recognize another of the same species? Researchers from the Columbia University Medical Center in New York say they have uncovered the brain region responsible for this process - known as social memory.
The hippocampus is an area of the brain that is known to be associated with memory.
According to the researchers, recent studies have shown there are subregions in the hippocampus that have different responsibilities.
They note that the dentate gyrus subregion allows us to distinguish between different environments, the CA3 subregion enables us to recall memories from partial cues, and the CA1 subregion plays an important role in all areas of memory.
But there is another subregion in the hippocampus between CA3 and CA1, called CA2. Until now, scientists have been unclear on what role this subregion plays in memory.
Inactivated CA2 region led to a lack of social memory
To find out, the researchers were able to selectively block CA2 neurons in the adult offspring of a transgenic mouse.
Researchers found that mice with an inactivated CA2 region in the brain lacked social memory.
These mice were then subject to a series of behavioral experiments. When it came to social memory, the researchers found that the mice were displaying interesting behavior.
"Normally, mice are naturally curious about a mouse they've never met; they spend more time investigating an unfamiliar mouse than a familiar one," explains first author Dr. Frederick L. Hitti.
"In our experiment, however, mice with an inactivated CA2 region showed no preference for a novel mouse versus a previously encountered mouse, indicating a lack of social memory."
On conducting two other experiments in the CA2-deficient mice, which tested how they recognized new objects through vision and smell, the researchers found the mice acted normally. This indicates that the CA2 subregion may be solely responsible for social memory.
CA2 potential new target for treatment of social disorders
The investigators say these findings may have important implications for behavioral disorders, such as autism, schizophrenia and bipolar disorder, since these conditions are associated with impaired social memory.
They say previous studies have shown that people with schizophrenia and bipolar disorder have less active CA2 neurons, compared with healthy individuals.
Furthermore, research has shown that people with autism have impaired signaling of vasopressin - a hormone that is thought to play a role in social behavior.
Prof. Steven A. Siegelbaum, senior author of the study, says:
"Because several neuropsychiatric disorders are associated with altered social behaviors, our findings raise the possibility that CA2 dysfunction may contribute to these behavioral changes."
The team concludes that based on these findings, the CA2 subregion may be a new target for the treatment of social disorders.
Late last year, Medical News Today reported on a study suggesting that a hormone called oxytocin activates social brain regions in children with autism.