While the rest of the body stops growing long beforehand, the brain seems to keep on developing into middle age, new research suggests. The findings could prove important in the prevention of age-related diseases such as Alzheimer's.

The brain is much more like a muscle than we ever thought. That is, the brain's structure does change over time and it may be possible to, in essence, "bulk up" the brain throughout much of adulthood.

Brain volume is commonly believed to stop expanding after age 20. But in MRI brain scans of 70 healthy men between the ages of 19 and 76, researchers found that the brain's white matter continued to increase until the mid- to late-40s.

Specifically, the brain kept growing in the temporal lobe and the frontal lobe -- the part of the brain that makes us human. This continued brain growth into middle-age can be associated with better emotional development and wisdom.

Knowing how the brain changes over time is important in understanding brain-related conditions ranging from schizophrenia to drug addiction to Alzheimer's disease. If the brain keeps maturing in adulthood, that means drug use, poor nutrition or other assaults on the brain could arrest a person's full development.

On the other hand, continuing to stimulate and challenge the brain throughout adulthood might promote its growth -- just as exercise builds muscle.

In the future, the brain imaging used in this study may help monitor age-related changes in people's brain volume and help signal deterioration before symptoms are apparent.