- See more Daily Mail on Google - save us as a Preferred Source It's time to rewrite the science textbooks – as a new study has revealed that the human brain is actually two separate organs.
Rather than being a single, unified organ, scientists from Stanford Medicine now say the human brain consists of two ancient nervous systems, cleverly packaged together.
A more primitive part regulates automatic functions that keep us alive: breathing, sleeping, and regulating our heartbeat and hunger urges.
The other handles higher-level thinking – language, consciousness and abstract reasoning.
Beyond rewriting the textbooks, the findings could open new avenues for studying devastating neurological diseases.
'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,' said Dr Kyle Loh, an author of the study.
'Our discovery means that we can now grow neurons from the back of the brain, the hindbrain, in a petri dish and study their functions.'
Rather than being a single, unified organ, scientists from Stanford Medicine now say the human brain consists of two ancient nervous systems, cleverly packagaed together
A more primitive part - the hindbrain - regulates automatic functions that keep us alive: breathing, sleeping, and regulating our heartbeat and hunger urges. The other is made up of the forebrain and midbrain, and handles higher–level thinking
The adult human brain is made up of three main regions: the forebrain, midbrain and hindbrain.
The forebrain handles higher-level thinking – things like language, consciousness and abstract reasoning.
The hindbrain, meanwhile, controls breathing, sleeping, and regulating our heartbeat and hunger urges, as well as the muscles of the face, tongue and throat, which affect speech and swallowing.
While the hindbrain is essential for keeping us alive, scientists have struggled to generate human hindbrain neurons in the lab. Sadly, this has limited the research possible on diseases affecting the brain stem – including spinal muscular atrophy and amyotrophic lateral sclerosis.
In their study, the team set out to understand why hindbrain cells are so much more difficult to generate than forebrain cells.
The team examined developing mouse embryos to understand exactly what happens as the brain takes shape.
Their observations revealed that the hindbrain follows a completely separate development pathway from the other regions of the brain.
In the forebrain and midbrain, developing cells express a gene called Otx2, while developing cells in the hindbrain express a gene called Gbx2.
The round the same two–origin brain pattern in chickens, zebrafish, and even acorn worms (brain pictured) – tiny creatures living on the ocean floor that share a distant common ancestor with humans
What's more, the researchers found fundamentally different forms of DNA packaging between the regions.
Dr Rayyan Jokhai, co-author of the study, explained: 'Previous attempts to make hindbrain neurons likely tried to coax forebrain and midbrain progenitors into hindbrain cells, which our study shows is not possible.'
Amazingly, this knowledge allowed the researchers to create functional hindbrain motor neurons in the laboratory for the very first time.
This could open the door to research on several debilitating diseases, including spinal muscular atrophy and amyotrophic lateral sclerosis.
'Now we have a model to better understand these devastating diseases, and work toward regenerative therapies for them,' Dr Jokhai said.
'This is a very exciting new frontier in brain research.'
To test their hypothesis, the researchers also looked back over 550 million years of evolutionary time.
They found the same two-origin brain pattern in chickens, zebrafish, and even acorn worms – tiny creatures living on the ocean floor that share a distant common ancestor with humans.
Dr Loh added: 'Our research suggests that evolution took two existing neural systems and pushed them together spatially.
'Having the brain as one organ would probably be more efficient, but we rely on this primordial way to make the brain as two separate pieces.'