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Scientists have always thought that a person is born with all the brain cells they'll get in their lifetime. However, recent studies revealed that the brain adds new cells during puberty to help navigate the complex social world of adulthood.

A new study, published in the journal Proceedings of the National Academy of Sciences, found that contradictory to past studies that suggest that such growth was limited to only two brain regions associated with memory and smell, researchers discovered that the mammalian brain also add cells during puberty in the amygdala and interconnected regions where it was thought no new growth occurred.

Researchers explain that the amygdala plays an important role in helping the brain make sense of social cues. For instance, the brain region helps hamsters picks up signals transmitted by smell through pheromones and helps humans evaluate facial expressions an body language.

"These regions are important for social behaviors, particularly mating behavior," lead author Maggie Mohr, a doctoral student in neuroscience at Michigan State University, said in a statement. "So, we thought maybe cells that are added to those parts of the brain during puberty could be important for adult reproductive function."

Researchers injected male hamsters with a chemical marker to show cell birth during puberty. The hamsters were allowed to interact and mate with females when they matured into adults. However, after each rendezvous, researchers would examine the brains of hamsters. 

The study found that new cells born during puberty had been added to the amygdala and associated brain regions. Researchers discovered that some of the new cells contained a protein that showed cell activation, which revealed that those cells had become part of the neural networks involved in social and sexual behavior.

"Before this study it was unclear if cells born during puberty even survived into adulthood," Mohr said. "We've shown that they can mature to become part of the brain circuitry that underlies adult behavior."

What's more, researchers found that more of the new brain cells survived and became functional in male hamsters raised in an enriched environment with a larger cage, running wheel, nesting materials and other features rather than those living in a plain cage.

Researchers hope that the current research also applies to humans.

"We don't know if cells are added to the human amygdala during puberty," researcher Professor Cheryl Sisk said in a statement. "But we know the amygdala plays a similar role in people as in hamsters. We hope to learn whether similar mechanisms are at play as people's brains undergo the metamorphosis that occurs during puberty."