Social Cells

Our sociability may depend on certain brain cells that are born during our adolescent years, a new study says.

"Ha-ha! Bobby has abnormal hippocampal neurogenesis!"

Healthy adult mice are generally pretty happy to interact with others of their species. But mice who don’t get much social interaction during their adolescence tend to treat other mice as alien objects, rather than as fellow rodents – in fact, they tend to actively avoid social encounters. (As I’ve pointed out a lot on this blog, mouse brains provide reasonably good models of many human brain functions, which is why neuroscientists study them.)

Though conventional wisdom used to say that adult brains don’t generate new neurons, scientists have actually known for years that neurogenesis – the birth of new neurons – is a process that begins in the womb and continues well into adulthood, especially in areas like the hippocampus, which is crucial for memory formation.

This study, however, is one of the first to link neurogenesis with social development. As the journal Neuroscience reports, a team led by Yale psychiatrist Arie Kaffman blocked the process of neurogenesis in adolescent mice. The researchers found that these mice not only had no interest in interacting socially with other mice – they actually tried to escape when normal mice tried to interact with them:

“These mice acted like they did not recognize other mice as mice,” Kaffman said.

Interestingly, mice whose neurogenesis was blocked during adulthood still showed normal social behavior, which suggests that neurogenesis during adolescence is particularly crucial for the development of healthy interpersonal instincts.

The researchers suspect that similar adolescent neurogenesis problems – either biological or environmentally triggered – may be responsible for human mental diseases that impair social functioning:

Schizophrenics have a deficit in generating new neurons in the hippocampus, one of the brain areas where new neurons are created. Given that symptoms of schizophrenia first emerge in adolescence, it is possible that deficits in generating new neurons during adolescence or even in childhood holds new insights into the development of some of the social and cognitive deficits seen in this illness.

In other words, neurogenesis in an teenager’s hippocampus may be a major determining factor in whether he or she is able to feel connections with other people, and develop normal intuitions about social behavior.

So, if you’ve been pestering your kids to “get out and make some friends,” now you have a solid neuroscientific reason to keep it up!

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