The Brain Detects Smells Before You Even Realize It

How does the brain tell a bad smell from a good one? Researchers at the University of Tokyo passed an electroencephalogram (EEG) to volunteers while they smelled rancid or rotting odors, fruity and flowery odors, and finally neutral odors.

” We were surprised to detect the signal corresponding to the smell very early on the EEG, as early as 100 milliseconds after the presentation of the smell, suggesting that the information representation of the smell is formed rapidly. “, said the doctoral student Mugihiko Katograduated from the University of Tokyo.

The brain detects an odor even before we are aware of it. © Irina Bg, Shutterstock

Bad odors detected before good ones

The brain detects the smell even before the person is aware of smelling something. The areas of cortex involved in odors activate between 300 and 600 milliseconds and beyond after the stimulus. It is at this moment that the brain knows if the smell is pleasant or not. Bad odors are detected from 300 milliseconds and pleasant ones from 500 milliseconds.

For scientists, the brain recognizes bad smells more quickly as a remnant of the past where they were a danger signal for our ancestors. This research could be useful in the context of Alzheimer’s disease or of Parkinson’s where the patients sometimes present disorders of thesmell.