Learn how experiences shape smell perception in brain

Researchers have unlocked the mystery of how our memories shape the way odour-sensory information is collected in the brain.

"We measured the activity of a group of inhibitory neurons that links the odour-sensing area of the brain with areas responsible for thought and cognition. This connection provides feedback so that memories and experiences can alter the way smells are interpreted," said Stephen Shea, assistant professor at the Cold Spring Harbor Laboratory here.

The experiences that we accumulate throughout life build expectations that are associated with different scents.

These expectations are known to influence how the brain uses and stores sensory information.

But researchers have long wondered how the process works in reverse.

"The inhibitory neurons that forge the link are known as granule cells," Shea added.

They are found in the core of the olfactory bulb, the area of the mouse brain responsible for receiving odour information from the nose.

Granule cells in the olfactory bulb receive inputs from areas deep within the brain involved in memory formation and cognition.

Shea, along with researchers Brittany Cazakoff and Billy Lau, engineered a system to observe granule cells for the first time in awake animals.

Granule cells receive information from neurons involved in memory and cognition and relay it back to the olfactory bulb.

There, the granule cells inhibit the neurons that receive sensory inputs.

In this way, "the granule cells provide a way for the brain to 'talk' to the sensory information as it comes in," Shea said.

Every scent is made up of hundreds of different chemicals and granule cells might help animals to emphasise the important components of complex mixtures.

Granule cells provide the brain with an opportunity to filter away the less important odours and to focus sensory neurons only on the salient part of the stimulus.

"The interplay between a stimulus and our expectations is truly the merger of ourselves with the world. It is exciting to see how the brain mediates that interaction," Shea said in a paper published in the journal Nature Neuroscience.