Some regions of the adult brain stay as malleable as a baby’s brain, so we can grow new connections, strengthen existing connections, and even create new neurons, allowing all of us to be lifelong learners. We didn’t always think that. Until five or six years ago, the prevailing notion was that we were born with all of the brain cells we were ever going to get, and they steadily eroded in a depressing journey through adulthood to old age.
We do lose synaptic connections with age. Some estimates of neural loss alone are close to 30,000 neurons per day. But the adult brain also continues creating neurons within the regions normally involved in learning. These new neurons show the same plasticity as those of newborns.