Olfactory Implants on the rise to fix the dysfunctional system

Jaladhi Shah, Dr D. Y. Patil Biotechnology and Bioinformatics Institute, Pune

The aftermath of COVID-19 on the olfactory system:

Following the multiple waves of COVID-19 that the world has witnessed, a lot of people, infected or uninfected have been subject to making changes in their lives. One such lifestyle adjustment that a lot of COVID-19 patients have acclimatized themselves to, is the loss of olfactory function. We’re aware that people who are infected lose their sense of smell briefly until they’re COVID-19-free, however, a new concern is when the sense is not regained after 6 months as well. Anosmia- the loss of smell- was common before COVID-19 too and has been known to be caused by head trauma, age as well apart from the virus. Now, to fix the olfactory dysfunction, several approaches are being looked into, one being olfactory implants, which is a new technology on the rise.

The need for the implant and how do we go about it?

Olfactory implants basically work by sending out electrical signals to stimulate the brain and these help in restoring smell. Apart from safety, since signals stimulate the central brain regions, the feasibility of doing so must be assessed. The idea of the olfactory implant seems to be derived from the cochlear implant being used as a hearing aid for eons now. The size of the market for olfactory implants has drastically boomed after the spur of the Coronavirus. Statistics show that loss of smell lasted for 2 months in 1 out of 6 people and went up to 6 months for about 1 in every 20 people.

It is important to understand the mechanism behind how the olfactory system of our body works. Once odorant molecules come in contact with the olfactory epithelium after entering our nose, they bind to the sensory neuron’s receptors. These neurons rally the signal up the olfactory nerve, to a region on the exterior of the brain, called the olfactory bulb. From the olfactory bulb, the signals are again rallied to the brain’s primary olfactory cortex. This signal transduction into multiple parts of the body’s limbic system plays a role in connecting smell, memory, and emotions. Now, while each sensory neuron can express just one receptor, each receptor can bind to several odorants. This versatility allows people to distinguish among a huge number of odors.

Public acceptance of implants:

Using cochlear implants to ail deafness is a prime example of using electronic devices to restore bodily functions. These olfactory implants are composed of chemical sensors, processors, transmitters, and receivers, however, whilst for auditory implants, it is known that the fundamental element is frequency, for olfactory ones the element is unknown and the anatomy in the nasal region is way more complex than the ear. In a recent study, 3 out of 5 participants revealed to have been able to smell something onion-like after placing electrodes at 3 positions on the bone next to the olfactory bulb. To determine if people would actually consider getting the implant to fix their olfactory dysfunction, the attitudes of 61 people with olfactory impairment were studied and it was inferred that the more serious the damage, the higher the probability of them getting the implant.

The olfactory implant: revolutionary or unreasonable?

Currently, while we have a prototype that can only help differentiate between 4-5 odors but over time, olfactory implants shall become more capable. The only challenges the current researchers find such as the risk of infection can all be fixed in due course of time, at least until we find a better treatment for the loss of smell.

Also read: A Metabolomics approach: Lactobacillus acidophilus exposure to amoxicillin antibiotic

Reference:

1. Makin, S. (2022). Restoring smell with an electronic nose. Nature, 606(7915), S12–S13. https://doi.org/10.1038/d41586-022-01630-1

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