Study: Human brain evolved to predict smells
By Contributor
Of all our sensory organs, the sense of smell is often overlooked.
While visual, auditory, and tactile perception are important, the olfactory sense also plays a subtle yet meaningful role in our daily lives.
The animal brain has an amazing ability to recognize and associate smells entering the nostrils. However, according to a research study at Northwestern University Medicine, the brain is able to predict the smell even before it enters the nostrils.
The brain will can generate a “predictive template” that leads to expectation of a scent. This amazing ability has played an important role in animal evolution, allowing creatures to react faster and more accurately to a stimulus in the environment.
The research at Northwestern was led by Christina Zelano, postdoctoral fellow in the lab of associate professor of neurology, Jay Gottfried, M.D. Zelano believes that this predictive coding may not necessarily be a behavioral advantage for modern-day humans, it was extremely important throughout our history.
Yet even today, our sense of smell can play a role. Zelano uses the example of rotten milk. “If somebody hands you a bottle of milk and asks, ‘Is this milk rotten?’ there may not be any visual clues to help you accurately determine if the milk has spoiled, so you rely on your sense of smell,” Zelano said.
“Our study indicated that if your brain can successfully form a template of a rotten milk smell, then you would more accurately determine whether that milk is rotten and therefore you are less likely to get sick. These predictive templates can give us an important advantage.”
Experiments were held with subjects who were given two very different scents: watermelon and a Play-Doh-like smell. First, the test subjects were told that one of these scents would be administered to them and they would have to indicate if they could sense it. Sometimes, the scent was the same as foretold, sometimes it was different, and sometimes it was hidden in a mixture of other scents.
While this was going on, their brains were hooked up to a MRI scanner with which the researchers could monitor their brain activity. They compared the brain activity when the subject was told of the scent to when they actually received the scent. It turns out the brain activity is more correlated when the scent was the same as foretold.
“Our study confirmed the existence of predictive coding mechanisms in olfaction,” said Gottfried, senior author of the study. “We found that the entirety of the olfactory cortex we looked at did form predictive templates that were very specific to the targeted smell.”
This was the first predictive template study to be performed on this evolutionary ability of the human olfactory cortex. It has been published in the journal, Neuron.
- Link to published article: http://www.sciencedirect.com/science/article/pii/S0896627311007318
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