Unpleasant odors are registered in the brain particularly fast and at an early stage of olfactory information processing

Localizing the human brain response to olfactory stimulation: A meta-analytic approach. A.Torske, K. Koch, S. Eickhoff, J. Freiherr. Neuroscience & Biobehavioral Reviews, December 27 2021. https://doi.org/10.1016/j.neubiorev.2021.12.035

Highlights

•  This paper provides the scientific community with an all-encompassing, up-to-date perspective on the human olfactory cortex through the quantification of all relevant and available data by implementing a robust meta-analytic approach.

•  The human olfactory cortex exhibits distinct activation patterns for different odor categories.

•  The neural underpinnings of the human sense of smell allows for a deeper understanding of human behavior through the extraction of valuable odorous information from the environment.

Abstract: The human sense of smell and the ability to detect and distinguish odors allows for the extraction of valuable information from the environment, thereby driving human behavior. Not only can the sense of smell help to monitor the safety of inhaled air, but it can also help to evaluate the edibility of food. Therefore, in an effort to further our understanding of the human sense of smell, the aim of this meta-analysis was to provide the scientific community with activation probability maps of the functional anatomy of the olfactory system, in addition to separate activation maps for specific odor categories (pleasant, food, and aversive odors). The activation likelihood estimation (ALE) method was utilized to quantify all relevant and available data to perform a formal statistical analysis on the inter-study concordance of various odor categories. A total of 81 studies (108 contrasts, 1053 foci) fulfilled our inclusion criteria. Significant ALE peaks were observed in all odor categories in brain areas typically associated with the functional neuroanatomy of olfaction including the piriform cortex, amygdala, insula, and orbitofrontal cortex, amongst others. Additional contrast analyses indicate clear differences in neural activation patterns between odor categories.

Keywords: Olfactory cortexSmellNeuroimagingActivation likelihood estimationMeta-analysis