Brain's hidden split

Scientists thought the brain was one organ, but new research shows it's two distinct systems that evolved separately over hundreds of millions of years.

“We've shown for the first time that the front of the brain arises from a totally different progenitor cell than the back of the brain”

Two brain systems

The human brain has two ancient nervous systems: one that controls basic functions like breathing and heartbeat, and another that enables human traits like poetry and math.

Why it matters

This discovery explains why scientists have struggled to grow certain brain cells in labs and opens new ways to study diseases like spinal muscular atrophy and ALS.

The breakthrough

Researchers found two brain progenitor cells that never overlap: one becomes the front brain, the other the back brain, with completely different genetic patterns.

“Previous attempts to make hindbrain neurons likely tried to coax forebrain and midbrain progenitors into hindbrain cells which our study shows is not possible”

Lab growth success

Scientists first grew functional hindbrain neurons from human stem cells, which can now be studied for diseases affecting the brain stem.

Evolutionary link

The same two-brain pattern exists in chickens, zebrafish, and acorn worms, showing this split evolved over 550 million years ago.

Disease implications

This research helps understand spinal muscular atrophy and ALS, which affect brain stem neurons and cause swallowing and breathing problems.

Obesity connection

The hindbrain regulates hunger, which explains how weight-loss drugs like semaglutide work by targeting these circuits.

Key researchers

Kyle Loh, PhD, lead researcher, says the brain's split explains why scientists have struggled to grow hindbrain neurons in labs for decades.

Future work

Researchers aim to study spinal cord development and how spinal muscular atrophy and ALS damage hindbrain neurons.

Evolutionary insight

The brain evolved from two separate neural systems that merged over time, creating a more complex but less efficient structure.

Patient impact

This discovery could lead to new treatments for spinal muscular atrophy and ALS by growing brain stem neurons in labs.

Long-term vision

Researchers hope to unlock more mysteries of the brain, including how neural systems develop and interact.

Funding sources

The study was supported by NIH, NSF, Stanford, and foundations focused on spinal muscular atrophy research.

Key findings

The hindbrain and forebrain develop from separate cells with no overlap, explaining why scientists couldn't grow hindbrain neurons before.

Historical context

This discovery overturns the long-held belief that the brain develops from a single progenitor cell that creates all brain parts.