Monitoring a 29-year-old woman's brain was the least puzzling thing: It revealed that she lacked the brain structures she needed to smell, but could still smell even better than the average person. .
It turns out that she is not the only one with this mysterious ability, according to a new study published today (November 6) in the journal Neuron . Researchers have found a small group of people who seem to oppose medical science: They can smell despite the absence of "olfactory bulbs", the area in front of the brain that processes information about nasal odors . It is not clear how they are able to do this, but the findings suggest that the human brain may have a greater capacity to adapt than previously thought.
A group of researchers in Israel made this discovery by accident: They conducted a different study involving the imaging of the brains of patients with normal sense of smell using magnetic resonance imaging (NMR) images . But they noticed that a woman seemed to be missing her olfactory bulbs.
Scientists believe this is surprising, since the advertisement for their study noted that participants should have good sense of smell and, nevertheless, based on their brain scans, a woman should not be able to smell. The researchers thought "she may not have noticed" that part of the ad, said senior author Noam Sobel, a professor of neurobiology at the Weizmann Institute of Science in Israel. But when asked, she said she had very good sense of smell.
So Sobel and his team asked if they could do more scans and tests and found that there was really olfactory a little better than the average person. "Our understanding is that odors are essentially mapped on the surface of bulbs," and the brain is somehow reading this map, Sobel told Live Science. If you miss this card, you should also lack the ability to smell, he added.
By deciding to continue this, researchers are hiring more people as "controls" to compare to the unusual case. All of these controls were women and all leftists like the original theme. "Lo and behold, in the ninth scan of the control," we found another woman with no olfactory bulbs and perfect sense of smell, "said Sobel. At that moment," it started to look like no accident. "
Fragrance imprint in the world
decided to search a database called the Human Connectome Project, published over 1100 MRI scans, along with participants' olfactory information. Researchers found that out of 606 women, three did not have olfactory bulbs, but still retained the ability to smell (a one of the three is left-handed).
no more brain scans and odor tests on both women and another woman who also lacked her olfactory bulb but could not smell.This third subject had an innate anosmia or inability to smell all her life. found that a woman with congenital anosmia cannot smell most odors, while the other two women can smell as well as people with olfactory bulbs.
As a final step, researchers want to create an "olfactory perceptive imprint" that documents what the participants' world smells like. To do this, they asked women and 140 other women of similar age to evaluate how similar smells are to each other, such as lemon and orange or lemon and skunk. The fingerprints of both women without olfactory bulbs were comparable to the fingerprints of the other participants. Moreover, the fingerprints of the two women were closer to each other than to the other two participants.
There are, however, slight differences. For example, neither can detect the smell of rose, which is one of the most common odors in sense of smell, said John McGan, an associate professor in the psychology department at Rutgers University, who was not part of the study.
"Surprisingly, it is not entirely shocking, as there was a previous report that similarly authentically showed a person who may have olfactory smell," without a olfactory bulb, he told Live Science, (This study was published in 2009 in American Journal of Rhinology ). But the sense of smell of this object was not so great compared to these new objects. So this study is a "stronger and convincing demonstration" that proves that "some people may have some sense of smell, even though they don't have olfactory bulbs," McGan said.
There were rodent studies in the 1980s and 1990s that suggested that if they removed their olfactory bulbs, they could still smell. But "these studies [were] have been quite torn apart in our area; they were really hammered 'for methodological problems,' said Sobel. "Who knows, maybe I'll be torn up now, too," he said. That's because finding them is contrary to dogma – the textbook definition of olfactory bulbs says they are "extremely important" to the sensory system, he added. What is happening?
The Nose of the Brain
It is not clear why this ability was detected only in women, especially in left-handed women. Most brain scanning studies exclude left-handed participants to reduce participants' differences, which may be why this was not discovered before, Sobel said. This is because people who are right handed may have brains connected in a different way than those who are left handed.
It is also not clear how these women developed sense of smell in their brains without having olfactory bulbs. But there are several hypotheses that can explain what's happening, Sobel said. The first is that these women were born without olfactory bulbs and then somehow, since their brains evolved at an early age, they found a way to make the smell work, which would testify to how "plastic" it is "The brain," he said. In other words, another region of the brain may take on the task of conveying aroma information to the brain.
A more exciting alternative might be that "you don't need olfactory bulbs" to detect, distinguish and identify odors, he said. That means that the smell works much differently than we think, and the olfactory bulb does something else, he added. For example, most mammals, when they smell something, have to make two decisions – what the smell is and where it comes from. Perhaps the olfactory bulb serves to understand where the smell comes from, but not what the smell is, he said. But it's all speculative and needs to be tested, he added.
Thomas Cleland, associate professor and professor in the department of psychology at Cornell University, who was also not part of the study, said he believed it was unlikely that the nerves that make up the olfactory bulbs were actually missing in these patients. "It is more likely that the corresponding scheme or something resembling it is somehow replaced, internally anatomically disorganized and / or differently shaped, unlike the missing ones," he told Live Science in an email. "And if that is true, it is not so strange that these women may smell somehow normal.
But if there is some displaced structure," you would expect that there would be some anomaly in their scan. "said Joel Mainland, an associate member of the Monell Chemical Senses Center in Philadelphia, who was also not part of the study." The idea that there may be a different structure that [taking] has over the role of the olfactory bulb would be surprising and incredible. "
The findings are "quite contrary to most of what the field thinks," Mainland told Live Science. "I think it's pretty critical to understand what's going on."
Originally published on Live Science .