People who have better spatial memory are also better at identifying odors, according to a new study.
The findings build on a previous theory that the main reason we evolved a sense of smell was to help us with navigation, since most animals rely primarily on smell to find food and avoid predators.
Researchers hypothesized that if this were indeed the case, there would be a strong link between navigation and olfaction.
Here, there, and everywhere
The new research shows that similar regions of the brain (the hippocampus and the medial orbitofrontal cortex) are both involved in these seemingly very different activities. They also discovered that the medial orbitofrontal cortex (mOFC), which is known to be involved in olfaction, is also critical to spatial memory.
To test this correlation between spatial memory and the sense of smell, researchers asked 57 participants (all young men and women) to do a couple of different tasks relating to spatial memory. In one, they gave participants about 20 minutes to explore a virtual city, traveling down every street and passing key landmarks (schools, a pool, and shops). Then researchers asked participants to find direct routes between some of the landmarks.
“The fact that both functions seem to rely on similar brain regions supports the idea that they were systems in the brain that were evolving at the same time…”
After that, researchers asked participants to identify 40 different smells, such as basil, strawberry, and cinnamon.
Researchers used structural MRIs to look at various regions of the brain known to be related to olfaction and spatial memory and found that participants who were good at both spatial navigation and identifying smells tended to have a bigger right hippocampus (an area of the brain known to be involved in long-term memory) and a thicker left mOFC.
Since previous research had not yet found an association between the mOFC, known to be critical for olfaction, and spatial navigation, the researchers confirmed their results through another experiment involving nine people with damage in this area of the brain.
They found that patients with mOFC damage exhibited both olfactory and spatial memory deficits, while patients with damage elsewhere in the brain did not exhibit these deficits.
“We weren’t sure, going in, that we would find that people who were better at identifying smells would also be good at navigating,” says Louisa Dahmani, who did the research during her doctoral work at McGill University and is currently doing a postdoc at Harvard University. “So the results came as a real surprise.”
“The fact that both functions seem to rely on similar brain regions supports the idea that they were systems in the brain that were evolving at the same time—though this is theory, rather than anything we set out to show in this paper,” says lead author Véronique Bohbot from McGill’s psychiatry department and the Douglas Mental Health University Institute. All we can say for sure is that we now know a bit more about the brain systems involved in both navigation and olfaction.”
The research appears in Nature Communications. The Natural Sciences and Engineering Research Council of Canada and the Canadian Institutes of Health Research funded the work.
Source: McGill University