Quirks & Quarks

Sniffing your way around: Our brains are built to navigate by scent

Researchers have found that those who can smell well, navigate well too

Researchers have found that those who can smell well, navigate well too

In an experiment to prove the theory that sense of smell evolved to aid in navigation, people were asked to identify 40 different smells. (McGill University)
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Originally published on November 10, 2018.

A new study suggests an intimate link in the brain between the ability identify smells and the ability to navigate a complex environment.  

The study by Louisa Dahmani and her colleagues in the Departments of Neuroscience and Psychiatry at McGill University in Montreal, puts a recent theory about the evolution of the sense of smell to the test. The theory proposes that the the sense of smell evolved to aid in navigation.  Ancient animals would have evolved a sense of smell to find food, and locate mates and predators, and so smell would have been intimately connected with location and navigation.

Dahmani and her colleagues hypothesized that this would imply a strong link between spatial memory and olfactory in the brain. 

Participants in the experiment put their skill navigating around a virtual city similar to this one, to the test. (Aljulla, GNU General Public License)

Follow your nose

The team conducted an experiment in which 57 participants were asked to navigate their way around a virtual city. They were then tested on their knowledge of specific routes between different places; for example finding the fastest route from one landmark to another. They were then asked to identify 40 different common smells, like strawberry, vanilla and cinnamon.

They found that the participants who were good at finding their way around the virtual city, were also very good at identifying smells. 

Each of the 40 'Sniffin Sticks' from the experiment includes a different scent. (McGill University)

Bigger and thicker brain

The researchers used structural magnetic resonance Imaging to look at the regions of the brain known to be related to spatial memory and olfaction, the hippocampus and the medial orbitofrontal cortex. 

The hippocampus, particularly the right hippocampus, is known to be associated with memory, specifically long-term memory. The medial orbitofrontal cortex is known to be related to olfaction, but as it turns out, it is also critical to spatial memory.

Analysis of the structural MRI's revealed that those who were good at both navigation and smell tended to have a bigger right hippocampus, and the left side of the medial orbitofrontal cortex was thicker.

Dahmani and her colleagues also think that because smell and spatial memory rely on similar brain regions, those regions may have been evolving at the same time.   

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