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 we have been able to monitor the activity of thousands of individual sensory neurons in the living nasal epithelium of genetically altered mice. When we apply mixtures of odors we find 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 we test for similar effects in humans using psychophysical techniques we find similar interactions between odors in a blend. 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 completed his PhD in Neurobiology with Frank Werblin at the University of California at Berkeley in 1987, where he elucidated the electrophysiological characteristics of olfactory sensory neurons. He was a post doctoral fellow at Yale University Medical School with Gordon Shepherd where he continued his pharmacological investigations of olfactory coding, asking how the olfactory system detects and discriminates a remarkably large and diverse set of chemical compounds that we call odors. He became an Assistant Professor at Yale in 1990 and in 1991 he joined the faculty of the Department of Biological Sciences at Columbia as an Associate and later Full Professor. During his 25 year tenure at Columbia he has received continuous funding from the NIH and has received Whitehead and McKnight Foundation Awards.
Dedicated to promoting the accessibility of science to a public audience Firestein serves as an advisor for the Alfred P. Sloan Foundation’s program for the Public Understanding of Science, where he reviews scripts for the Ensemble Studio Theatre/Sloan Science and Technology Program, and for the Tribeca and Hamptons