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The gene responsible for social memory
  
By Scott Holmer

Scientists recently found the gene responsible for constructing social memory. According to the July issue of Nature Genetics, researchers at Emory University School of Medicine in Atlanta, Georgia, discovered that the oxytocin gene enables an individual to recognize someone previously encountered.

If the oxytocin gene is missing or defective, then severe deficits in social memory occur. "Without this fundamental ability, even your own mother would remain a stranger," study author James T. Winslow told the press. With the help of some transgenic or "knockout" male mice who lacked the oxytocin gene, researchers were able to expose the link between genetics and social memory.

In order to test the social behaviors of mice, Winslow and his team closely observed the way mice use their sense of smell. A normal male mouse will use its sense of smell in order to "get to know" a female mouse until she becomes familiar. If a male and female are reintroduced 30 or 60 minutes after separation, the male mouse will not spend as much time reacquainting himself with the familiar female. Unlike normal mice, the knockout male mice would spend the same amount of time smelling or getting to know each female even if they had previously met. The data imply that without an operative oxytocin gene, the knockout male mice are unable to remember social encounters.

Both the normal and the transgenic mice showed no defect in their sense of smell because both normal and knockout mice had the same level of success in an olfactory-guided foraging task and reacted normally to a non-social olfactory stimulus. The spatial memory of knockout and normal mice was intact as defects in the oxytocin gene solely affect social memory.

The research team also demonstrated that it was possible to repair social memory in the transgenic mice by injecting low doses of oxytocin. Once injected they decreased the time spent socializing with familiar females.

The oxytocin gene is embedded in the genomes of all mammals including humans. Defects in the gene could contribute to autism, schizophrenia and other diseases evidenced by social isolation and disconnection.

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Ferguson, J.N., Young, L.J., Hearn, E.F., Matzuk, M.M., Insel, T.R., & Winslow, J.T. Social amnesia in mice lacking the oxytocin gene. Nat Genet 25, 284-288 (July 2000).
 

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