According to a new study, published in the journal Neuron, there is a group of people who possess the ability to smell, despite lacking the region of the brain that processes this information.
The discovery, which suggests the human brain may have a greater ability to adapt, happened by chance after researchers at the Weizmann Institute of Science in Israel found that a 29-year-old woman who was missing “olfactory bulbs”, the region in the front of the brain that processes information about smells from the nose, could smell better than the average person.
After identifying the anomaly, the researchers recruited more people, who were also left-handed and female, to see if the ability was unique to the woman.
“Lo and behold, we discovered another woman without olfactory bulbs and a perfect sense of smell,” senior author Noam Sobel, a professor of neurobiology at the Weizmann Institute of Science in Israel, told Live Science. “It started to look like no coincidence.”
The finding prompted the researchers to search through a database called the Human Connectome Project, which has more than 1,100 published MRI scans, as well as information about the participants’ smell.
The researchers found that of the 606 women analysed, three didn’t have olfactory bulbs but still had the ability to smell. One of the women was left-handed.
The phenomenon was not detected in men, however, and researchers are unsure why gender or left-handedness are factors.
Further research through the use of olfactory perceptual fingerprints showed that the sense of smell in the two women without olfactory bulbs was comparable to 140 similarly aged women.
Interestingly, while the women could rate how similar smells such as orange and lemon are, they were unable to detect rose-like odours.
Overall, the research shows that it is possible for some women who are left-handed and born without olfactory bulbs, previously considered “utterly essential to the sensory system”, to smell.
As for why this may be the case, the scientists only have hypotheses as of now.
According to Professor Sobel, the first reason may be that these women were born without olfactory bulbs and then found a way “to make smell work” during infancy as their brains developed – which would attest to “how plastic the brain is”.
A second hypothesis is that we “don’t actually need olfactory bulbs to detect, discriminate and identify smells,” which would mean the olfactory bulb has a different function – possibly locating a smell rather than actually identifying it.
While more research is required to reach a conclusion, Professor Sobel told the BBC the latter hypothesis is a “dramatic alternative” to what we previously thought we understood about smell.