In Catalonia, neuroscience research is helping explain why smell can shape mood, memory and mental wellbeing so strongly. The sense of smell is often treated as secondary, but researchers say it has a direct route into the brain’s emotional and memory systems.
Laura López-Mascaraque, a research professor at the Cajal Neuroscience Centre in Madrid, said olfactory neurons in the upper part of the nose are unusual because they regenerate every 40 to 60 days. She said that with training, people can maintain smell function into older age. News
Smell works differently from the other senses. Volatile molecules enter the nose, activate receptors on olfactory neurons and send signals to the olfactory bulb. From there, the information goes straight to the olfactory cortex, within the limbic system, rather than first passing through the thalamus.
That direct pathway helps explain why a smell can trigger a vivid memory. López-Mascaraque said the olfactory system connects closely with the amygdala, which handles emotions, and the hippocampus, which handles memory. She linked this to the Proustian effect, named after Marcel Proust’s In Search of Lost Time, where a madeleine dipped in tea brings back a flood of memories.
She also said some smells leave a stronger mark than others, especially those tied to childhood or to strong emotions. A study in Science cited by López-Mascaraque suggested people can detect millions of different smells, because a smell is not a single molecule but a mix of molecules in different concentrations.
According to López-Mascaraque, whether a smell feels pleasant or unpleasant is shaped in part by culture and by the brain’s reward system. She said aromatherapy is not medicine, although some smells may help certain people relax or sleep. She also noted that around 400 genes, about 2% to 3% of the human genome, are linked to smell, which helps explain why olfactory perception varies so much from person to person.
Looking ahead, researchers are working on digital olfaction, including sensors that could detect disease in a similar way to dogs that identify certain pathologies by smell. They are also developing wearable sensors that could detect allergens or gluten near food. For more on the science behind this work, see the Cajal Neuroscience Centre and the Spanish National Research Council.