The next time you need to get somewhere, you may be able to follow your nose.
A small study has found that a strong sense of smell is associated with a strong sense of direction. So while you may not be able to smell your way to a destination (unless it's a bakery), an ability to identify distinct smells could indicate an ability to get where you need to go.
It may sound a little off-kilter, but scientists think it has to do with how many animals navigate the world.
Smell your way through the world
In 2012, Lucia Jacobs, an animal behaviorist at Berkeley, proposed that the size of the olfactory bulb, the neural structure that helps all animals smell, was less about "odorant discrimination and acuity" and more about navigation. Her paper, published in the Proceedings of the National Academy of Sciences, suggested that this reasoning explained why there was a pattern in the scale of olfactory bulb sizes in animals, even those that relied more on their eyes than their noses to survive.
Jacobs' paper maps a number of debates and inquiries about how the olfactory system functions, how it evolved and its relative size in animals compared to other parts of the brain. She tracks the size of the olfactory bulb and mapping abilities across mammals, birds, reptiles, fish and arthropods to build a case for her hypothesis.
To do a simple test of Jacobs' hypothesis, researchers conducted a small experiment at McGill University in Canada in 2018, suggesting that the ability to identify smells was associated with spatial memory, or the ability to learn and develop relationships between landmarks in an area to create a type of cognitive map. Navigating by landmark requires a part of the brain that includes the hippocampus, a region of the brain associated with short- and long-term memory, along with spatial memory, and the medial orbitofrontal cortex (mOFC), a region associated with olfaction, but one that hasn't been proven to be involved with spatial memory, according to the researchers.
How the experiment worked
Fifty-seven young adults were recruited to participate in a virtual "wayfinding task" in which they had to make their way around a simulated environment. After 20 minutes of familiarization of the virtual city and having passed by each of eight landmarks at least twice, the participants were placed in front of one of the landmarks and asked to find the most direct route to one assigned by the researchers.
The participants also smelled 40 scented felt-tip pens one at a time. After a brief sniff, the participants chose from one of four words on a screen that best identified the smell.
An additional exercise involving a virtual maze was used to determine if the participants were more likely to rely on landmarks to navigate or if they used a stimulus-response method of navigating, a process of navigation that's more habit-based and built over time as people travel the same route over and over again. Finally, MRI scans were conducted to determine the thickness of the mOFC and the hippocampal volume.
What the researchers found, and published in the journal Nature Communications, was that those with the ability to correctly identify the smells of the pens also had the easiest time navigating the wayfinding task by way of landmarks. A strong sense of smell was not identified in the participants who were stimulus-response navigators. Additionally, the participants who had a strong sense of smell and navigation abilities displayed not only more hippocampal volume in their MRI scans but a thicker mOFC. This, the researchers say, provides some evidence for the role of the mOFC in spatial memory.
The researchers performed another small study involving nine individuals not involved in the first study who had lesions on their mOFC. Therese participants demonstrated a reduced ability to accurate identity smells and relied less on landmarks to navigate. They did, however, perform better on the maze than the other group, a finding that the researchers took to indicate the a thicker mOFC may interfere in some fashion with stimulus-response navigation.
The connection between sense of smell and navigation, the researchers suggest, likely came about as a result of the parallel evolution of these neural systems. The original function of the olfactory sense in humans may have been intended to support our spatial memory — just like the homing pigeons in the famous experiment.
Keep that in mind the next time you get lost going to the dentist. It won't help you from getting horribly lost, but it's good food for thought along the way.