Intro
In this episode of the Huberman Lab podcast, Dr. Andrew Huberman interviews Dr. Noam Sobel, a renowned researcher in the field of olfactory perception. They discuss how smells influence our hormones, health, and behavior. Dr. Sobel shares fascinating insights into the human sense of smell and its impact on various aspects of our lives.
Main Takeaways
Humans’ Ability to Smell
- Humans can smell things around them as well as dogs can.
- Humans are incredibly good at sensing the chemical world around them.
- Humans take chemicals from others and process information about them to determine many things about them, including how stressed they are, their hormone levels, and the impact on emotions and decision making.
The Olfactory System
- Our sense of smell involves both the nose and the mouth, with retro nasal olfaction being a big part of the contribution of olfaction to food and taste.
- The olfactory epithelium is the sensory surface of the olfactory system, with about 6-7 million receptors in humans, and 350 different kinds of receptors.
- A meaningful percentage of our genome is devoted to the kinds of olfactory receptor subtypes we have in our nose.
- Bloodhounds do not have a billion receptors in their nose, as previously believed, but the exact number of receptors in the human nose is hard to count.
- The study of olfaction is important for understanding our subconscious abilities, including pheromones.
The Link Between Smell and Memory
- Smell and memory are closely linked, and there is a direct path from the nostrils to the hippocampus, which is one of the primary encoding centers of memory.
- Olfactory memories are formed more easily and maintained longer than other types of memories.
- The first exposure to a smell generates a particularly robust representation in the brain.
- There’s something special about olfaction that makes it etched into our being.
Improving Sense of Smell
- Humans have an incredible sense of smell with a detection threshold of 0.2 parts per billion, making it one of the most remarkable senses in the mammalian world.
- Humans can improve their sense of smell, especially if they are deprived of other senses like vision and touch.
- A study was conducted on people following an odor trail using only their sense of smell, and they were able to improve their ability to track scents quite robustly.
- Participants in the study were able to detect a no-dirt called estraterrenol at a concentration of 10 to the negative 12 molar in the liquid phase, which is equivalent to detecting a drop of liquid in two Olympic-sized swimming pools.
Impact of Smells on Behavior and Health
- Our sense of smell is linked to our autonomic nervous system, which has a sympathetic and parasympathetic nervous system that drives the switch from left to right nostril.
- The shift from side to side in our nostrils becomes pronounced during sleep and is linked to balance in the autonomic nervous system.
- The sympathetic nervous system generates patterns of alertness while the parasympathetic nervous system is associated with rest and digestion.
- Nasal halter measurements can differentiate between ADHD and non-ADHD adults.
- Understanding and gaining control over the nasal cycle could potentially be used to cure ADHD and other diseases.
Smells and Social Interactions
- Humans subconsciously code identification of people they interact with through olfaction.
- Hand-shaking is a behavior that could potentially involve olfaction.
- People tend to touch their face more after a handshake.
- A study found a remarkable increase in hand-to-nose behavior after a handshake.
- Smelling a lemon may not necessarily be a result of olfactory receptors, but rather trigeminal receptors.
Medical Applications of Olfaction
- Loss of sense of smell is an early sign of neurodegenerative disease.
- There is a link between congenital anosmia and hormonal abnormalities, particularly in Kalman syndrome.
- Olfaction and reproduction are tightly linked in humans and all mammals.
- Metabolites have a smell, and every disease has a specific metabolic process, which means that medical diagnostics could be done through odor transmission in the future.
Digitizing Smell and Olfactory Research
- Recent breakthroughs in olfactory research have led to the development of an algorithmic framework that can predict the perceptual similarity of any two molecular mixtures with very high accuracy.
- Google is trying to digitize smell through an offshoot startup called Osmo, and other companies are trying to do the same.
- The potential applications for odor transmission go beyond just transmitting recipes and food smells, with medical diagnostics being a possibility.
- It will take time for olfaction digitization to reach the level of 4K vision and audition.
Summary
The Power of Human Smell
Humans have an incredible sense of smell, comparable to that of dogs. Our ability to sense the chemical world around us allows us to gather information about others, including their stress levels, hormone levels, and emotional impact. Tears of others can even impact our hormone levels in powerful ways. The olfactory system, involving both the nose and mouth, plays a significant role in our perception of food and taste.
The Intricacies of the Olfactory System
The olfactory system is a complex network of receptors in the olfactory epithelium. While the exact number of receptors in the human nose is hard to count, it is clear that a significant portion of our genome is devoted to olfactory receptor subtypes. The study of olfaction is crucial for understanding our subconscious abilities, including pheromones. Smell and memory are closely linked, with olfactory memories being formed easily and maintained longer than other types of memories.
Improving Sense of Smell and its Impact on Behavior
Humans can improve their sense of smell, especially when other senses like vision and touch are deprived. Tracking scents and detecting minute concentrations of odorants are possible with training. Our sense of smell is linked to our autonomic nervous system, with the shift from side to side in our nostrils reflecting patterns of alertness and rest. Understanding and gaining control over the nasal cycle could potentially be used to treat ADHD and other diseases.
Smells and Social Interactions
Humans subconsciously code identification of people they interact with through olfaction. Hand-shaking may involve olfaction, as people tend to touch their face more after a handshake. Smelling a lemon may not necessarily be a result of olfactory receptors, but rather trigeminal receptors. The impact of smells on social interactions and behavior is significant.
Medical Applications and Olfactory Research
Loss of sense of smell is an early sign of neurodegenerative disease, and there is a link between congenital anosmia and hormonal abnormalities. Olfaction and reproduction are tightly linked in humans and all mammals. Recent breakthroughs in olfactory research have paved the way for digitizing smell and odor transmission. Medical diagnostics could potentially be done through odor transmission in the future.
Conclusion
The sense of smell is a powerful and fascinating aspect of human perception. It influences our behavior, memory, and even our health. Olfactory research is shedding light on the intricacies of our olfactory system and its potential applications in various fields. As we continue to explore the world of smells, we gain a deeper understanding of ourselves and the impact scents have on our lives.
