Our brains contain 鈥渂anana鈥� neurons that fire when we see or smell the fruit, or even just hear the word 鈥渂anana鈥�, hinting at how concepts are encoded within the brain.
We already know that several brain regions 鈥� including the piriform cortex, amygdala, hippocampus and entorhinal cortex 鈥� are responsible for processing smells, but until now no one had ever explored the role of individual brain cells, or neurons.
To fill this gap, at the University Hospital Bonn in Germany and his colleagues analysed the brain activity of 17 people with epilepsy, who had already been fitted with up to 12 brain-implant electrodes as part of their treatment.
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The team asked participants to sniff samples of 15 different odours, including banana, liquorice, anise, orange, garlic and coffee, and recorded their brain activity. They then trained an AI model to link smells to electrical signals from neurons.
Once trained, the AI could identify an odour from previously unseen signals with more than 60 per cent accuracy. The researchers were also able to identify a single neuron in the amygdala that increased firing in response to the image or smell of a banana, or the word 鈥渂anana鈥�. Another neuron in the piriform cortex fired in response to the concept of liquorice expressed as an image, smell or word. Other neurons in the amygdala also seem to respond more strongly to smells that the participants liked, firing more often than for smells they disliked.
While previous work has shown that we have neurons that encode for concepts 鈥� sometimes known as 鈥済randmother neurons鈥� or 鈥淛ennifer Aniston neurons鈥�, 聽it is impressive to make the same link with smells, says at the Francis Crick Institute in the UK.
鈥淚t is one of those rare studies recording individual neurons in humans, which is essential if we want to understand the mechanisms of how our brains work,鈥� he says.
Nature
