Brain processes unpleasant odors faster than pleasant ones

(ORDO NEWS) — Japanese scientists investigated when and where information about various odors is processed in the human brain.

It turned out that the speed of processing depends on the quality of the smell: the brain most quickly perceives unpleasant odors, it takes more time for pleasant ones, as well as for smell recognition.

Scientists from the University of Tokyo (Japan) found out at what point our brain perceives and processes information about various smells.

The study showed that in the early stages of processing such information in the brain has nothing to do with its recognition. However, in the later stages, unpleasant odors are processed faster than pleasant ones.

Japanese scientists have developed a special device that accurately transmits the smell into the human nasal cavity.

Participants rated the properties of ten different odors while their brain signals were recorded using electroencephalography (EEG).

The researchers processed the data obtained using machine learning methods, which made it possible for the first time to see with unprecedented spatial and temporal resolution when and where the brain processes various smells.

The first signals on the EEG appeared as early as 100 milliseconds after the “presentation” of the smell. Thus, information about it is transmitted to the brain extremely quickly.

The brain detected smells even before the subject consciously perceived them, which happened only after a few hundred milliseconds.

Odor characteristics, including pleasantness or unpleasantness, were encoded by different spatial and temporal processing in the cerebral cortex.

The concept of the unpleasantness of a smell appeared in the brain earlier than that of pleasantness and other qualities.

Unpleasant odors, such as the smell of rotten meat or rotten meat, were distinguished from neutral and pleasant odors by the brains of the participants as early as 300 milliseconds after “presentation”.

At the same time, the recognition of pleasant smells, for example, color or fruit, occurred only after 500 milliseconds – approximately at the same time when the subject understood which smell was presented to him. 600-850 milliseconds after the onset of the smell, areas of the brain involved in emotional and semantic processing, as well as memory, became active.

According to scientists, the early perception of unpleasant odors may have evolved as an early warning system of potential dangers.

Smell disorders can be an early symptom of neurodegenerative diseases such as Parkinson’s and Alzheimer’s, so studying the neurobiological basis of odor processing will help to better understand these disorders and find new ways to diagnose them in a timely manner.


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