Are you born with all your brain cells, or do you grow new ones?

Most of the neurons in your brain were created before you were born. But some areas of the brain make new neurons after birth in a process called postnatal neurogenesis.

A few areas, including the cerebellum and the prefrontal cortex, continue adding new neurons in infancy.  And scientists believe that at least one region of the brain — the hippocampus — continues to create new neurons throughout life.

Interestingly, this brain region is involved in learning and memory. The hippocampus forms memories of events and experiences. Some scientists believe the addition of new neurons to the hippocampus may enhance learning and memory because new neurons are more plastic than older neurons, meaning they can more easily modify their connections to form and store memories.

Though the hippocampus provides the best evidence of neurogenesis in the adult brain, it’s possible that other parts of the brain have the same capabilities, and new and improving technologies may help us determine if this is the case. In fact, recent evidence suggests that adult neurogenesis also happens in the human striatum, a brain region important for forming habits. There is also hope that understanding adult neurogenesis will allow us to harness this power to repair and replace neurons lost through injuries and diseases — but that would be well into the future.

It’s worth noting that neurons aren’t the only cells that make up the brain. Scientists have long observed that the brain’s other cells, or glia, also regenerate. Glia, whose duties include maintaining the blood-brain barrier, protecting neurons from pathogens and controlling neuron function, make up about half of the human brain’s mass and are renewed and replaced on a continuing basis. So there is much more turnover of cells, both neurons and glia, in the brain than you might think.

Editor’s note: This article has replaced an earlier version, which no longer reflected current scientific consensus.