Scientists say the human body has a 'hidden' SIXTH sense - and it's vital for our health

It is a question that feels like it should have a straightforward answer: how many senses do humans have?

Growing up, most of us learned that there are five main senses – sight, smell, hearing, taste, and touch.  

However, it might be time to rewrite the textbooks.

Scientists from Scripps Research say the human body has a 'hidden sixth sense', called 'interoception'. 

Interoception is an 'understudied process', by which your nervous system continuously receives and interprets your body's physiological signals to keep vital functions running smoothly. 

It helps to explain how your brain knows when to breathe, when your blood pressure drops, or when you're fighting an infection, according to the researchers.  

Now, the team has received a $14.2 million award from the National Institutes of Health (NIH) to get to the bottom of this mysterious sense once and for all. 

'Interoception is fundamental to nearly every aspect of health, but it remains a largely unexplored frontier of neuroscience,' said Professor Xin Jin, who will lead part of the study. 

Interoception was first proposed in the early 20th century by a British neuroscientist called Charles Sherrington. 

However, it was largely ignored by researchers until around 10 years ago. 

The five classic senses – sight, smell, hearing, taste, and touch – are external, and rely on specialised sensory organs. 

For example, sight relies on your eyes, while smell requires your nose.  

In contrast, interoception operates through a network of neural pathways, deep within the body. 

For this reason, the researchers have dubbed it the 'hidden sixth sense'. 

While interoception is vital for interpreting how you feel at any given moment, it has been largely unexplored until now. 

'Signals from internal organs spread widely, often overlap and are difficult to isolate and measure,' the researchers explained in a statement. 

'Sensory neurons that carry these messages weave through tissues—ranging from the heart and lungs to the stomach and kidneys—without clear anatomical boundaries.'

With the new funding, the Scripps Research team will now attempt to chart how sensory neurons connect to a wide range of internal organs, including the heart and the gastrointestinal tract. 

They will then try to build the world's first atlas of this internal sensory system. 

Beyond rewriting the textbooks, the researchers say that decoding interoception could have important implications for treating disease. 

Previous research has shown that problems with neural pathways are linked with a range of conditions, including autoimmune disorders, chronic pain, and high blood pressure. 

In an article for The Conversation, Jennifer Murphy from Royal Holloway, University of London, and Freya Prentice, from UCL, explained how interoception is also important for mental health. 

'It contributes to many psychological processes – including decision making, social ability and emotional wellbeing,' the pair explained. 

'Disrupted interoception is even reported in many mental health conditions – including depression, anxiety and eating disorders. 

'It may also explain why many mental health conditions share similar symptoms – such as disturbed sleep or fatigue.'

Overall, the researchers hope their atlas will answer key questions about how the internal organs and nervous system stay in sync. 

'By creating the first atlas of this system, we aim to lay the foundation for better understanding how the brain keeps the body in balance, how that balance can be disrupted in disease and how we might restore it,' Professor Jin added.