Israeli scientists: Some women smell without olfactory bulbs

Israeli researchers have found that some women’s brains are able to detect smells even though they lack the part of the brain that processes odor.

According to a study published this week in the journal Neuron, researchers at the Weizmann Institute of Science made the discovery by accident when examining brain scans of young female volunteers for an unrelated study.

Researchers noticed that one volunteer lacked an olfactory bulb, but had a better sense of smell than her peers who possessed the bulbs, thought necessary to identify odors.

At first, professor Noam Sobel and his team thought the observation was a mistake, or that the 29-year-old woman was exaggerating when she claimed to have a better sense of smell than most people.

“We tested her smelling faculties in every way would could think of, and she was right,” Sobel said in a statement. “Her sense of smell was indeed above average. And she really doesn’t have olfactory bulbs. We conducted another scan with especially high-resolution imaging, and saw no signs of this structure.”

An MRI of two brains. Both the woman on the left, who has intact olfactory bulbs and the woman on the right, who is missing them, have excellent senses of smell. (courtesy Weizmann Institute of Science)

It has been long thought that without olfactory bulbs it would be impossible for the brain to perceive smell.

The phenomenon observed in the woman stumped Sobel and his team, so they began to look at a public library of over a thousand MRI scans.

It wasn’t long before the researchers found another instance of the phenomenon in another left-handed woman in their control group.

“Alarm bells started ringing,” Dr. Tali Weiss said.

Sobel and his team then launched a full study to better understand the brain anomaly.

A subject taking an electro-olfacto-gram test in the lab of Prof. Noam Sobel at the Weizmann Institute of Science in Rehovot. (YouTube screenshot)

After closely examining 606 MRI scans of young women, researchers found that 0.6 percent of them could identify and discriminate between smells just as well as someone with bulbs.

Interestingly, that number jumped to 4.25% among left-handed women, but the phenomenon was not observed at all in men.

Sobel and his team said they could not explain the phenomenon, or the apparent link to gender and left-handedness.

Professor Noam Sobel of the Weizmann Science Institute in Rehovot. (Courtesy)

One possibility is that the women’s olfactory bulbs are significantly smaller than in other individuals, and therefore are nearly impossible to see on a regular brain scan.

Another possibility is that some women’s brains are able to adapt to the lack of olfactory bulbs during early childhood, by assigning the task of detecting smell to another part of the brain.

Sobel and his team also suggested that perhaps the current scientific assumption on the role of olfactory bulbs is incorrect.

“Current ideas posit the olfactory bulb as a ‘processing center’ for information that is complex and multi-dimensional, but it may be that our sense of smell works on a simpler principle, with fewer dimensions. It will take high-resolution imaging – higher than that approved for use on humans today – to resolve that issue,” Sobel said in statement released by the school.

“But the fact remains that these women smell the world in the same way as the rest of us, and we don’t know how they achieve this.”