Discover the Science of Smell

The Incredible Science of Olfaction and Chemosensation

Dr. Noam Sobel is a neurobiology professor at the Wiseman Institute of Science who studies olfaction and chemosensation.
Humans have a strong sense of smell and can detect chemicals in their environment just as well as dogs can.
When people meet, they exchange chemicals from their body and surroundings, which can affect their emotions and decision-making at a subconscious level.
Tears from others can impact one's hormone levels.
Humans have a regular alternation of ease in which they can breathe through one nostril or the other, reflecting an underlying dynamic of their nervous system and affecting alertness.
Dr. Sobel's laboratory discovered that humans are always sensing their own odors, which can impact their cognition and behavior.
Dr. Huberman first became aware of Dr. Sobel's work when he observed people following a scent trail experiment on the UC Berkeley campus.
The olfactory system involves receptors in the olfactory epithelium in the nose, with humans having around 6-7 million receptors of around 350 different kinds.
Odorants from the environment interact with these receptors and undergo transduction into a neural signal.
This neural signal travels via the olfactory nerve to the olfactory bulb, which is the first target in the brain.
Losing one's sense of smell due to trauma is often caused by damage to the cribriform plate at the back of the head, which can sever the olfactory nerve.
The olfactory sensory neurons can regenerate, but if the nerve is completely severed, the sense of smell is lost forever.Olfactory System and Memory: Facts and Discoveries
Olfactory neurons can regenerate, but only if there is partial damage or if there is a remnant left after an injury.
The general rule is that if a person does not recover their sense of smell within a year to a year and a half, they will never get it back.
Alpha lipoic acid can accelerate the recovery of smell, and olfactory training can help maintain the connections of olfactory neurons.
The olfactory system is the only system that undergoes systematic neuro regeneration in the adult mammalian brain.
The olfactory system follows the most extreme case of convergence in the mammalian nervous system.
Every receptor type is responsive to a small subset of different molecular shapes, which are known as autotopes.
The olfactory system has a map reflecting receptor identity, and each receptor subtype has a glomerulus that reflects it.
Information from the olfactory system projects widely from the olfactory bulb to several targets in the brain, including the primary olfactory cortex and the hippocampus.
The first exposure to a smell generates a particularly robust representation more than other sensory stimuli, according to a study called "The Privilege Representation of Early Olfactory Associations."
There is something special about olfaction, and olfactory memories are formed more easily or maintained longer or more robustly than other sorts of memories.
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Humans have a remarkable sense of smell, and olfactory training can improve their ability to track scents quite robustly, especially if we deprive them of vision and somatic sensations.The Incredible Abilities of the Human Sense of Smell
Humans have a remarkable sense of smell and can detect certain scents at incredibly low levels, such as mercaptans in cooking gas, which can be detected at 0.2 parts per billion.
Humans can track scents like a dog, as demonstrated in an experiment where a participant was blindfolded and successfully tracked a chocolate bar dragged across the grass.
The experiment was turned into a study that found participants could track a consistent odor path in the grass and even improved with training, making the rate-limiting factor the speed at which they could crawl.
The study also found that having two separate nostrils contributed to better tracking performance, utilizing the information from each nostril to locate scents.
The nasal cycle, where one nostril has higher airflow than the other in a periodic pattern, is linked to balance in the autonomic nervous system and can be measured with a wearable device called the nasal halter.
The nasal halter can distinguish between adults with ADHD and those without, as well as whether they are taking Ritalin.
The alternating flow of air through one nostril or the other is not fully understood and is currently being studied to determine whether it drives the shift in the autonomic nervous system or is merely reflective of it.
Yoga practitioners claim to have control over their nasal cycle but were unable to willfully switch between left and right nostril flow in a study with 14 participants.
The nasal cycle becomes more pronounced during sleep, with one nostril closing completely and the other opening fully.
The sense of smell is processed through the olfactory epithelium and bulb in the brain, which has a representation on both sides of the brain, much like our eyes and ears.
The ability to track scents and distinguish between them is a highly evolved trait in mammals, with humans ranking among the best.
Understanding the mechanics of the human sense of smell and the nasal cycle can have potential applications in disease diagnosis and treatment.The Role of Nasal Inhalation in Cognitive Processing and Neurodegeneration
Participants are being exposed to pain through a cold water hand exposure paradigm.
The exposure to cold water generates a shift in the nasal balance, potentially driven by autonomic arousal.
The nasal cycle phenomenon has little to do with preferential processing of olfactory information in terms of right brain left brain.
The sniffing brain approach suggests that nasal inhalation is timing and driving many aspects and patterns of neural activity and cognitive processing.
Nasal inhalation is believed to have evolved to be meaningful in brain processing in general, not only in olfactory information.
Nasal inhalation is found to be timing cognitive processing and modulating it, which is great for cognition and health.
Eyes are two pieces of the brain extruded from the cranial vault, while the olfactory sensory neurons are right there at the tops of the nostrils.
Loss of the sense of smell is one of the earliest signs of neurodegenerative diseases, such as Alzheimer's and Parkinson's.
Olfactory loss is an early sign of neurodegeneration, and there is a theory that Alzheimer's may be the result of a pathogen that enters the brain through the olfactory system.
Olfaction has not been effectively digitized, which is why olfactory tests are not as convenient as delivering stimuli in vision and audition.
Congenital anosmia is a condition where people are born without the sense of smell, and they suffer socially, have reduced social contacts and romantic social contacts, and die younger.
Kalman syndrome is a condition where there is hypogonadic development in men and where practically all are anosmic.