Thomas Hummel describes the international efforts made to help patients with a loss of sense of smell. This could be due to COVID-19 or other diseases such as chronic rhinosinusitis and neurodegenerative disorders.

Hummel mentions the development of cochlear implant to help those with hearing loss. He says that similar implants could be placed inside the nasal cavity and connected to the bulb of the olfactory, which would elicit a pattern to the brain.

Hummel, a doctor who also works in clinical research, describes his career path as being more dependent on international collaborations than other areas of clinical research. When you are working in cardiovascular disease, you can always find someone who is also interested in cardiovascular disorders. The difference is in the sense of scent. “You look around and there is nobody.”

The series features world-renowned brain scientists who discuss their careers, collaborations and societal impact.

COVID-19 is often characterized by a loss of smell. Thomas Hummel describes international efforts to assist patients in regaining their smell.

Welcome to Tales From The Synapse. This podcast is brought to you in partnership by Nature Careers and Nature Neuroscience.

Jean Mary Zarate is a senior editor for the journal Nature Neuroscience. In this series, we interview brain scientists from around the world to learn about their lives, their research, collaborations and the impact of the work they do.

In episode nine we meet a leading researcher in the field of olfactory research who is working on implants to help patients with COVID 19 that have lost their sense of smell.

Thomas Hummel is my name. I am a smell and taste specialist at the otolaryngology department of the Technical University of Dresden, Germany.

It’s part of the department of Otolaryngology. Since I am a medical physician, I have specialized in taste and smell disorders for a long period of time. Since around 30 years, I have worked in the field of sense of smell. Since about 20 years ago, or even a bit longer, I’ve been treating patients with taste and smell disorders.

We are a small group, with between 5 and 15 members. We try to recruit students and diagnose those with olfactory losses and offer them therapy.

We also, at the same, do research on the physiology and chemical senses. This includes gustation, trigeminal sensitive in the nose and olfaction.

Gulpation is the functionality of sweet, sour and bitter taste. The nose is where the trigeminal function lies. You can feel it as if you were burning, biting or stinging. All of these sensations are trigeminal.

We perceive odors through olfaction. They are a complex thing, but odors can be very complex.

We are trying to look into this further. Not only here, but also in a group that is very international when it comes to chemistry.

As soon as you begin to work with the chemical senses you will be automatically connected with many people from different countries, because so few people are interested in that.

You’ll find that working in cardiovascular disease is different. Just look around and you’ll see someone who is working on cardiovascular diseases. The sense of smell is different. Look around and you’ll see nobody.

My thesis was on chemical senses, and I began in Erlangen in Bavaria, Germany, near Nuremberg.

The senses were of interest to me. My wife actually introduced me to it. I was a participant in one of the studies she conducted. She was right, because her thesis was one of the first to look at the electrophysiological equivalence between the senses of smell and EG related compounds.

She needed subjects, so she hired me. I was her victim in this study. And I was happy to oblige and became interested in it. My supervisor Gerd Kobal was a pioneer in this field. With him, I wrote my thesis on trigeminal sensitivities. The pain was mainly in the nasal cavity. From there, I worked on a sense or smell. So I broadened my horizons in several areas, and branched out into different ones.

As a kid, I had no prior knowledge of the chemical senses. I believe I acted like most children. Being interested in nothing and everything.

My interest in smell developed only later. This is sort of how I see life. You start something, and then have to decide what you want to do. You can go left, right or take a turn.

The next time you turn right, you’ll end up in a place you already know.

At least, I enjoyed it. I hope this will be useful to you, and maybe others as well. That’s where I am from.

The olfactory or sense of smell is based on at least two pillars.

The olfactory is one. In a way, that’s how you perceive odors. This is located in the nasal cavities and in the roof of your nasal cavity.

There are about 5 square centimetres of olfactory sensors in the upper part.

These receptors are contacted by the molecules of odor that reach the nasal cavity.

You must first penetrate the mucus on the top of the mucosa. It’s because of the mucus that it is called mucosa.

They penetrate the membrane, making contact with receptors. They may activate the receptors with a bit of luck. If enough receptors are activated, it produces a sensation.

The signals are then transmitted to the bulb. This is the first relay station of the brain, which is crucial for olfactory perception.

It is about 12 millimetres in length and 10 millimetres in thickness.

It’s just a sausage lying there. As a German, I like to compare it to sausages.

The odors then activate the bulb. If enough activations occur, the odorous stimulation is transmitted to other brain areas.

At the olfactory level, a pattern is created. Let’s take vanilla as an example. Vanilla does not activate one vanilla cell, but a type of cell within the cavity.

Vanilla activates two different receptor types in the olfactory epithelium. The pattern they produce is transferred to the bulb.

Vanilla, we can perceive a pattern behind vanilla. This pattern may overlap with other odors. It’s just a pattern. This is why we have, in terms of olfactory code, about 400 different types of receptors that are developed within the olfactory Epithelium.

Some of them can be activated only by one smell, while others are activated when they are exposed to other odors.

These 400 receptors, which are based on pattern recognition (if you consider the combinations of receptors), can encode for an almost infinite number of odorants. We can then perceive them. We can’t name them, but we are able to perceive them and perhaps also differentiate them.

In reality, we probably have a lot less odors in our lives that are important. It’s a question that is still unresolved, just how many odors are important in our daily lives.

One estimate comes from a Munich study that looked at food and the importance of odors in foods. It’s around 250.

Surprisingly, there are only a few of them that are actually important. We can, however, detect theoretically millions of different smells.

There are many different types of odors. In real life, we may not need as many odors, or at the very least, those that we can perceive.


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