Scientists find brain contains two distinct nervous systems

A study reported by ERR suggests that the human brain consists of two separate nervous systems that were compressed together during evolution. One supports functions such as language, abstract thinking and dreaming, while the other regulates automatic processes including breathing and heartbeat.

Researchers at Stanford University in the United States reached the conclusion while studying mouse embryos during the early stages of development. They found that the front of the brain develops from a different type of progenitor cell than the rear, which controls vital functions such as breathing, swallowing and heart activity.

The two cell populations never overlap during development. Instead, they proceed along parallel paths from beginning to end, with their genetic material packaged in fundamentally different ways already during the embryonic stage.

The researchers said this divided structure is not unique to humans. Looking back more than 550 million years, they found the same arrangement in chickens, zebrafish and tiny acorn worms living on the ocean floor, which share a very distant common ancestor with humans.

According to the researchers, the arrangement developed when evolution brought two existing nervous systems together because of limited space. Although a brain developing from a single type of cell might be biologically more efficient, humans still rely on this hundreds-of-millions-of-years-old inheritance.

The findings could also have implications for medicine. Earlier attempts to grow nerve cells from the rear of the brain used the wrong starting material and failed. After identifying the correct starting point, the researchers were able to grow fully functioning hindbrain nerve cells in laboratory conditions.

The rear of the brain also contains circuits that regulate hunger, meaning the approach could eventually support research into weight loss. The researchers published their findings in Nature Neuroscience.