Sniffing out the brain’s predictive power: Human brain smells what it expects rather than what it sniffs

Sniffing out the Brain’s Predictive Power: Human Brain Smells What It Expects Rather Than What It Sniffs

ScienceDaily (Oct. 6, 2011) — In
the moments before you “stop and smell the roses,” it’s likely your
brain is already preparing your sensory system for that familiar floral
smell. New research from Northwestern Medicine offers strong evidence
that the brain uses predictive coding to generate “predictive templates”
of specific smells — setting up a mental expectation of a scent before
it hits your nostrils.


 

he researchers used functional MRI techniques and cutting-edge,
pattern-based analysis to identify the existence of predictive coding in
the olfactory cortex of the brain, where the sense of smell is housed.
(Credit: Image courtesy of Northwestern University)

 

Predictive coding is important because it provides animals — in this
case, humans — with a behavioral advantage, in that they can react
more quickly and more accurately to stimuli in the surrounding
environment.

The study, published in the Oct. 6 issue of the journal Neuron,
was led by Christina Zelano, a postdoctoral fellow in the lab of Jay
Gottfried, M.D., associate professor of neurology at Northwestern
University Feinberg School of Medicine and attending physician at
Northwestern Memorial Hospital.

The researchers used functional MRI techniques and cutting-edge,
pattern-based analysis to identify the existence of predictive coding in
the olfactory cortex of the brain, where the sense of smell is housed.

While it may not be obvious that predictive templates in the
olfactory system give modern-day humans a behavioral advantage, Zelano
said people often overlook the power of the sense of smell.

“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.”

In the study, subjects performed “odor search tasks” while being
monitored inside an MRI scanner. The two scents used in the study were a
watermelon smell and a Play-Doh-like smell.

Before each trial began, subjects were told which of two target
smells they should try to identify. A visual countdown, informing the
subjects that they should get ready to receive a specific odor was
administered and then, after smelling the odor, subjects indicated by
pressing a button whether they thought the target smell was present.
Sometimes the target scent administered was the same as the subject was
foretold, sometimes it was different, and sometimes the target scent was
hidden in a mixture of other scents.

The researchers were able to look at the activity pattern of the
brain before any odor arrived and found that, for trials where the
target was the same, the activity pattern was more correlated than when
the target was different.

“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. ”

 

via Sniffing out the brain’s predictive power: Human brain smells what it expects rather than what it sniffs.

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