Brain and Behavior

Sensation and Perception

How does the brain process smell?

The sense of smell is processed in the olfactory system, which is an evolutionarily ancient system, dating back hundreds of millions of years. The olfactory system responds to airborne chemicals, which waft into the nose. The olfactory nerve connects the olfactory receptor cells in the nose to the olfactory bulbs, two small structures on either side of the brain just below the frontal lobe. From the olfactory bulbs, axons bundled together into the olfactory nerves project to various parts of the limbic system. From there, neurons connect to other subcortical areas such as the thalamus, hypothalamus, and insula. Thus, the olfactory nerve sends information directly to the emotional centers of the brain, without the filtering role of the thalamus or the cortex. The olfactory bulb plays a much larger role in simpler and phylogenetically older animals than it does in phylogenetically younger and more complex animals like primates.


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