A New Scent-sation

Out of all of our five senses, the sense of smell is probably the most likely to fall into the category of “you don't know what you have until it's gone.” It is quite easy to overlook how important the sense of smell is in our everyday lives — our sense of taste is heavily reliant on it, as is our ability to detect dangerous substances, like those emanating from a gas leak. Because of where scent information is processed in the brain, the memories and emotional responses normally triggered by certain smells are also a thing of the past. When you really take stock, a lot more than just the ability to recognize scents is lost along with the sense of smell.

Those with brain injuries and certain medical conditions have known this for a long time, but the myriad issues associated with anosmia (that is, the inability to smell) have recently come to the forefront as a result of COVID-19. One study reported that up to 1.6 millions Americans are likely to have lost their sense of smell for six months or longer as a result of a COVID-19 infection. Work being done in a lab at Virginia Commonwealth University may one day be able to restore the sense of smell to those suffering from anosmia. While this work is still in the early stages, the results that have been seen thus far show promise.

There are two primary components to this research — there is an eyeglass-mounted e-nose that is capable of detecting the chemical signature of various odors, and there is also an interface with the brain that simulates the experience of those odors in an individual that is otherwise incapable of sensing them. There are many details of this technique that have yet to be worked out, but the e-nose portion is presently more fully developed.

The e-nose consists of gas sensors made of semiconductor materials. When a molecule of interest interacts with this semiconductor, it changes its degree of electrical resistance. This resistance can be measured to determine how much of that molecule is present in the environment. This is not a novel technology, but the size of these sensors is shrinking, which is making them much more suitable for use in a wearable device, like the eyeglasses demonstrated by the researchers. With present technologies, these devices are limited to distinguishing between just a few odors, which is a far cry from the trillion or so odors our olfactory system can sense. As a stopgap, the team is planning to initially offer support for the detection of a few safety-related smells (e.g.: smoke, gas), and a few pleasurable smells (perhaps customized to each user’s tastes). As e-nose technology advances, this set of recognizable scents would expand.

Upon detecting a particular scent, the device currently illuminates a light to indicate its presence, but the ultimate goal is to make the wearer of the device experience the smell via a brain implant. This portion of the work is much more hypothetical and untested, however, the basic principles are built on solid ground. Using arrays of electrodes to stimulate the brain have found some limited success in restoring other senses, such as touch, vision, and hearing in the past. However, the researchers still are unsure of many key considerations, like what part of the brain to stimulate, or what pattern of stimulation will result in the experience of a particular scent.

These are major hurdles to be sure, but the team is very optimistic. They think many of these challenges can be overcome within just a few years. With the increasing incidence of anosmia related to COVID-19, interest in such a device has skyrocketed, and they believe that may be the key to getting the support that is needed to solve these big problems.