Part of the Brain: The Inside Story exhibition.

By the time you reach your twenties, your brain is functioning at its peak. How does your brain change as you age?

How it Works

Scientists once assumed that after early childhood, the number of neurons in the brain was fixed, and no new ones could ever form. But recent research has shown that new neurons form throughout life in at least two areas: the hippocampus, which helps memories form, and the olfactory bulb, which processes smell.

Like the rest of your body, your brain has a natural tendency to slow down over time. After your twenties, little by little, the number of neural connections declines. Your working memory may become a bit less reliable, and you may not focus as well or react as quickly as you were able to in your youth.

With an illness, the brain can dwindle more rapidly. One of the most common brain disorders in people over 50 is Alzheimer's disease. While the causes of this illness are still unknown, it is clear that Alzheimer's destroys neurons and the connections between them. Under a microscope, Alzheimer's tissue shows fewer neurons and fewer synapses than normal. Damage starts in an area near the hippocampus, the brain's memory center. This is why one of the first signs of Alzheimer's is difficulty with memory.

In a normal aging brain, however, lessons learned through many years of experience are retained. Studies suggest your brain will stay healthy longer if you keep it engaged with mental and physical exercise; in fact, the more actively you use your brain, the more likely it is to stay sharp as long as you live.