The Nose Knows More Than We Think

         The intoxating smell of bacon permeates the kitchen. The spring flowers bloom and envelop the atmosphere with their natural scents. Smoke from a nearby bonfire on the beach signals the beginning of summer. These stimuli are sensed by the nose, which houses specialized structures that sense odorants (molecules that produce smells) and relay information to the brain through their association with brain cells. Our noses are able to detect a wide range of smells, and several publications have estimated that the human nose can detect 10,000 different scents.

          However, a report in Science estimates that one trillion scents can be detected by the human nose. Researchers at Rockfeller University developed a set of criteria that allowed for the generation of various odor combinations, which they provided to subjects. The ability of the subjects to discriminate between different odor mixtures was measured, and the quantifications from these experiments were used to calculate their estimate.

          This article noted that one trillion is the lower limit of odors our noses can discern, meaning that the actual number may be much higher. This piece of news intrigued me and led me to think of physical properties that confer this capability. How many different olfactory receptors (proteins that bind odor molecules and facilitate the transfer of odor information to the brain) do we have? Do olfactory neurons, the cells through which olfactory receptors transmit signals, function as small or large groups? How would this activity be controlled? Our olfactory systems may be more complex than we previously believed.

          Furthermore, it will be interesting to determine the mechanism through which olfactory receptors process different odor molecules to allow for the brain to distinguish smells. Studying the means by which this sensory information is sorted and interpreted by the brain will also provide more insight into the development of this amazing ability. Until then, happy smelling!

The scent of a rose is composed of 275 odor components (Bushdid et al., Science 2014).

Courtesy: http://www.varietybackyard.net/ho-to-deal-with-some-common-diseases-of-roses/