Researchers at the University of Tokyo have been able to see when and where odors are processed in the brain with the help of a specially created odor delivery device. The study found that unpleasant odors are processed more quickly than pleasant odors when perception occurs later. Problems with odor perception can be an early symptom of neurodegenerative diseases, so uncovering more of the neural bases of odor perception could help towards better understanding of those diseases in the future.
Does the smell of coffee help you start your day? Can you not like the strong stuff? According to new research, how quickly your brain processes the smell of your morning beverage might depend on whether you think it's pleasant or not.
A team at the University of Tokyo created a device that can deliver 10 different odors in a timely manner. The pleasantness of the participants was rated by wearingEEG caps, which record signals inside the brain. The team was able to see when and where the range of odors was processed in the brain using machine learning-based computer analysis.
We were surprised that we could detect signals from presented odors as quickly as 100 milliseconds after odor onset, suggesting that representation of odor information in the brain occurs rapidly.
The odor was detected by the brain before the participant consciously perceived it, which took several hundred milliseconds.
The representation of unpleasantness in the brain emerged earlier than pleasantness and perceived quality, according to Project Associate Professor Masako Okamoto. When unpleasant odors were administered, participants could distinguish them from neutral or pleasant odors within 300 milliseconds. The representation of pleasant odors in the brain took 500 milliseconds to occur, around the same time as when the quality of the odor was also represented. Significant areas of the brain involved in emotional, semantic and memory processing became most involved after 600-850 milliseconds after odor onset.
The early perception of unpleasant odors may be an early warning system. The study helps us understand how the olfactory system works. It wasn't known that scalp- recorded EEG would allow us to assess odors from time periods as early as 100 milliseconds.
This high temporal resolution image of how our brains process odors may be a stepping stone towards better understanding the mechanisms of neurodegenerative diseases in the future, such as Parkinson's and Alzheimer's diseases, in which a malfunction in the sense of smell is an early warning sign. The team is interested in exploring other research avenues.
Funding.
This work was supported by the Grant-in-Aid for Scientific Research on Innovative Areas from Japan Society for the Promotion of Science.
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