Some left-handed women still have sense of smell even if they are missing crucial part of the brain

The human brain is able to process smells in some women even if they don’t have the olfactory bulbs in their brain that process odour, scientists have discovered.

When we smell something like a fresh pot of coffee, baked bread or something less pleasant, the smell goes in through the nose and excites nerve endings, which then create electrical signals to the olfactory bulbs.

It was previously thought that without the bulbs it would be impossible to process what you are smelling. 

People with no olfactory bulbs typically suffer from anosmia, or an inability to smell. it was previously thought it would be impossible for people with no olfactory bulbs to smell

However, scientists from the Weizmann Institute of Science in Israel studied the MRI scans of 606 women and found that 0.6 per cent of the women studied were able to smell despite not having any olfactory bulbs. 

Intriguingly, this increased to 4.25 per cent if the women were left-handed. 

The team then carried out more extensive tests on two of the women without olfactory bulbs and proved they could identify, detect, and discriminate between odours just as well as someone with bulbs. 

The ‘phenomenon’ only happens in women. Men without olfactory bulbs showed no sign of being able to smell. 

This picture shows a scan of a person with olfactory bulbs (upper left) is visibly different from the brain scans of people without olfactory bulbs (bottom and upper right). People without olfactory bulbs usually have no sense of smell

Researchers questioned whether the brain may have more plasticity, or ability to adapt, than previously thought if humans don’t need olfactory bulbs to smell. 

Professor Noam Sobel, senior author of the study, said: ‘The simplest interpretation of our findings is that these women were born without an olfactory bulb, but thanks to the extreme plasticity of the developing brain, they developed an alternative glomeruli map somewhere else in the brain, not in the olfactory bulb.  

‘Although such plasticity is amazing, it is not out of the realm of what we have seen in human development.’

Professor Sobel said he had no idea why left-handedness or gender made the difference in who could still smell without olfactory bulbs

The researchers have posed a number of reasons for the women’s ability to smell despite seeming to lack the necessary equipment, including the fact that the bulbs may be there but too small to see with an MRI scan.

Another, more controversial theory posed by researchers suggests that the olfactory bulbs may not be responsible for identifying smell but instead for locating where a smell originated. 

‘It was overwhelmingly shocking, this started ringing all the bells,’ Professor Sobel told BBC News.

He said he had no idea why left-handedness or gender made a difference to who could still smell without the bulbs. 

The team hopes to be able to find out through future research whether someone with anosmia could be taught to smell by triggering other parts of the brain to take over odour processing functions.

The study was published in the journal Neuron.