The brain adds new cells during puberty to help navigate the complex social world of adulthood, two Michigan State University neuroscientists report in the current issue of the Proceedings of the National Academy of Sciences.
Scientists used to think the brain cells you're born with are all you get. After studies revealed the birth of new brain cells in adults, conventional wisdom held that such growth was limited to two brain regions associated with memory and smell.
But in the past few years, researchers in MSU's neuroscience program have shown that mammalian brains also add cells during puberty in the amygdala and interconnected regions where it was thought no new growth occurred. The amygdala plays an important role in helping the brain make sense of social cues. For hamsters, it picks up signals transmitted by smell through pheromones; in humans, the amygdala evaluates facial expressions and body language.
"These regions are important for social behaviors, particularly mating behavior," said lead author Maggie Mohr, a doctoral student in neuroscience. "So, we thought maybe cells that are added to those parts of the brain during puberty could be important for adult reproductive function."
To test that idea, Mohr and Cheryl Sisk, MSU professor of psychology, injected male hamsters with a chemical marker to show cell birth during puberty. When the hamsters matured into adults, the researchers allowed them to interact and mate with females.
Examining the brains immediately after that rendezvous, the researchers found new cells born during puberty had been added to the amygdala and associated regions. Some of the new cells contained a protein that indicates cell activation, which told Mohr and Sisk those cells had become part of the neural networks involved in social and sexual behavior.