Scientists have long treated the brain as a single organ that grows from one pool of early cells. Stanford University neuroscientist Kyle Loh and colleagues challenge this view, arguing that the human brain is two distinct nervous systems that evolved separately and were joined together over hundreds of millions of years. The discovery could also help explain why researchers have struggled for decades to grow certain types of brain cells in a lab, and open new avenues for studying devastating diseases that affect the hindbrain, or brain stem, such as spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (also known as ALS or Lou Gehrig’s disease). — Read More

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