Modulation of the stimulus is a common property of sensory systems, including both inhibition and enhancement of selected inputs. In all known cases this modulation occurs at higher levels of processing, at synapses of relay neurons between the peripheral sensors and cortical brain regions. Similar modulation has been demonstrated in the flavor (olfactory and taste) system in humans in psychophysical experiments, and are assumed to be due to higher level processing.
Utilizing a new technique in microscopy it has been possible to monitor the activity of thousands of individual sensory neurons in the living nasal epithelium of genetically altered mice. By applying mixtures of odors the result is that a given odor species can act to activate, inhibit or enhance the response of other sensory neurons. That is, modulation of the olfactory stimulus appears to occur in the peripheral sensory cells, prior to any additional processing at higher centers.
When testing for similar effects in humans using psychophysical techniques, similar interactions between odors in a blend were discovered. This sets the olfactory system apart from other sensory systems and raises critical new issues as to how the nose and brain communicate to perceive a complex odor world.
Stuart Firestein is a Professor of Neuroscience at Columbia University. His research focuses on the vertebrate olfactory system, perhaps the best chemical detector on the planet. He received his PhD at UCAL Berkeley, completed his post-doctoral fellowship at Yale University Medical School, and joined Columbia in 1991.
The seminar reproduced in this video was presented at the 1st Spanish edition of Enforum Web (5-7 May 2020)