Now that's what you call mind-blowing! The human brain is TWO separate organs, scientists reveal

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

The two organs of the brain

The scientists say the human brain consists of two ancient nervous systems, cleverly packagaed together: 

1. A more primitive part regulates automatic functions that keep us alive: breathing, sleeping, and regulating our heartbeat and hunger urges.
2. The other handles higher–level thinking – language, consciousness and abstract reasoning.

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.'

Motor Neurone Disease (ALS): No known cure and half of sufferers live just three years after diagnosis

History 

The NHS describes motor neurone disease (MND) as: 'An uncommon condition that affects the brain and nerves. It causes weakness that gets worse over time.'

The weakness is caused by the deterioration of motor neurons, upper motor neurons that travel from the brain down the spinal cord, and lower motor neurons that spread out to the face, throat and limbs. 

It was first discovered in 1865 by a French neurologist, Jean-Martin Charcot, hence why MND is sometimes known as Charcot's disease. 

In the UK, Amyotrophic Lateral Sclerosis (ALS) is referred to as Motor Neurone Disease, while in the US, ALS is referred to as a specific subset of MND, which is defined as a group of neurological disorders.

However, according to Oxford University Hospitals: 'Nearly 90 per cent of patients with MND have the mixed ALS form of the disease, so that the terms MND and ALS are commonly used to mean the same thing.' 

Symptoms

Weakness in the ankle or leg, which may manifest itself with trips or difficulty ascending stairs, and a weakness in the ability to grip things.

Slurred speech is an early symptom and may later worsen to include difficulty swallowing food.

Muscle cramps or twitches are also a symptom, as is weight loss due to leg and arm muscles growing thinner over time.  

Diagnosis

MND is difficult to diagnose in its early stages because several conditions may cause similar symptoms. There is also no one test used to ascertain its presence.

However, the disease is usually diagnosed through a process of exclusion, whereby diseases that manifest similar symptoms to ALS are excluded. 

Treatment

There is no cure for MND and the disease is fatal, however the disease progresses at different speeds in patients.

People with MND are expected to live two to five years after the symptoms first manifest, although 10 per cent of sufferers live at least 10 years. 

Causes

The NHS says that MND is an 'uncommon condition' that predominantly affects older people. However, it caveats that it can affect adults of any age.

The NHS says that, as of yet, 'it is not yet known why' the disease happens. The ALS Association says that MND occurs throughout the world 'with no racial, ethnic or socioeconomic boundaries and can affect anyone'.

It says that war veterans are twice as likely to develop ALS and that men are 20 per cent more likely to get it.  

Lou Gehrig was one of baseball's preeminent stars while playing for the Yankees between 1923 and 1939. Known as 'The Iron Horse,' he played in 2,130 consecutive games before ALS forced him to retire. The record was broken by Cal Ripken Jr. in 1995 

Lou Gehrig's Disease

As well as being known as ALS and Charcot's disease, MND is frequently referred to as Lou Gehrig's disease.

Lou Gehrig was a hugely popular baseball player, who played for the New York Yankees between 1923 and 1939.

He was famous for his strength and was nicknamed 'The Iron Horse'. 

His strength, popularity and fame transcended the sport of baseball and the condition adopted the name of the sportsman.