All our lives we thought there was one brain — now it turns out that's not exactly true

A new study from Stanford University reveals that the human brain develops from two separate neural systems, not from a single origin as previously believed. Researchers identified two distinct types of neural progenitor cells as early as the embryonic stage, one leading to the development of the forebrain and the other to the hindbrain. The discovery could advance research into diseases such as ALS and SMA.

A new study from Stanford University challenges a centuries-old concept: the human brain actually developed from two separate neural systems, not from a single origin. The researchers, led by Dr. Jukai, examined the earliest stages of embryonic development and identified two different types of neural progenitor cells. One type expresses the Otx2 gene and is destined to become the forebrain and midbrain, responsible for language, consciousness, and abstract thinking. The second type expresses the Gbx2 gene and is destined to form the hindbrain, which includes the brainstem and systems vital for breathing, heart rate, sleep, and hunger regulation. These two cell populations do not overlap at all and are separate from the earliest stages. The researchers succeeded for the first time in causing human pluripotent stem cells to develop into functional motor neurons of the hindbrain. The ability to grow such cells could open new possibilities for researching SMA, ALS, and other diseases that affect the brainstem. The study also examined evolutionary history and found that the same pattern of two separate neural origins exists in chickens, zebrafish, and acorn worms. The findings may also have medical implications for weight-loss drugs based on semaglutide, which act on neural circuits in the hindbrain that regulate hunger. Researchers from the California Institute of Technology and the University of California, San Francisco also participated in the study.