HWN Suggests

Smells Ring Bells: How Smell Triggers Memories and Emotions

The answer is likely due to brain anatomy. Incoming smells are first processed by the olfactory bulb, which starts inside the nose and runs along the bottom of the brain. The olfactory bulb has direct connections to two brain areas that are strongly implicated in emotion and memory: the amygdala and hippocampus. Interestingly, visual, auditory (sound), and tactile (touch) information do not pass through these brain areas. This may be why olfaction, more than any other sense, is so successful at triggering emotions and memories.

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 The Smell of Evolution

We can distinguish between a vast number of different odors, thanks in part to the vast number of olfactory receptor genes our neurons can choose from. So far scientists have identified 390 different genes in the human genome that encode olfactory receptors.

 What's in a Nose? An Exploration of the Olfactory Epithelium

The olfactory epithelium is a layer of tissue at the top of our nasal cavities that is home to around 40-50 million hyper-sensitive receptor neurons. These neurons receive or intercept odour molecules (depending on how interesting you want to make it sound) and transmit signals to an olfactory bulb of nerves at the front of your brain, which decodes the signals and sends them along the olfactory tract deep into the cortex of your brain, which then interprets them as smells.

 ‘Smells’ and ‘Smellosophy’ Review: What the Nose Knows

What is a smell? Is it a substance, or a perception.

Articles of Interest

Do All Olfactory Cortices Send Feedback Projections to the Olfactory Bulb?

Olfactory sensory neurons, which sense volatile odor molecules in the nose, send their axons to the olfactory bulb (OB), the first brain area where odor information is processed. The OB receives a large number of centrifugal projections from multiple brain areas.

Effects of nasal inflammation on the olfactory bulb

Sinonasal diseases, such as rhinosinusitis, affect up to 12% of individuals each year which constitutes these diseases as some of the most common medical conditions in the world. Exposure to environmental pathogens and toxicants via the nasal cavity can result in a severe inflammatory state commonly observed in these conditions. It is well understood that the epithelial and neuronal cells lining the olfactory mucosa, including olfactory sensory neurons (OSNs), are significantly damaged in these diseases.

Humans have a better sense of smell than you think

In this case, the mechanism was the olfactory bulb, a brain structure that receives input from sensory neurons devoted to smell located in our nasal passage and sends those signals to the brain. Humans have a smaller olfactory bulb—relative to our brain size—than other animals. When Broca saw that humans not only possess puny olfactory bulbs, but also don’t seem to exhibit certain smell-compelled behaviors (we don’t really run around sniffing each other’s butts the way dogs do) he came to the conclusion that our sense of smell must be lacking. He missed that humans do indeed have some smell seeking behaviors—we tend to sniff our hands after shaking someone else’s hands, for example (whether or not we realize it).

Is the Olfactory Bulb Computationally Similar to the Retina?

The computational role of the olfactory bulb remains a mystery after 60 yr of physiological research. Recently, Fantana and colleagues proposed a new model of bulb function based on sparse inhibitory connections between glomeruli, the functional units of the bulb, rather than the existing lateral inhibition model. I present a summary of their model here and its implications along with comparison to recent work in the very similar Drosophila olfactory system.

Know Your Brain: Olfactory Bulb

Olfaction begins when odorant molecules enter the nasal cavity through inhalation or by rising from the mouth (e.g. during the chewing of food). Those molecules interact with olfactory receptors, which are part of a family of G-protein coupled receptors. Stimulation of these receptors causes the production of second messengers like cyclic AMP (cAMP), which leads to the opening of ion channels and the generation of action potentials in olfactory receptor cells.

Not to be sniffed at: human sense of smell rivals that of dogs, says study

McGann identifies a 19th century brain surgeon, Paul Broca, as the primary culprit for introducing the notion of inferior human olfaction into the scientific literature. Broca noted that the olfactory bulb – the brain region that processes odour detection – is smaller, relative to total brain volume, in people compared with dogs or rats. The discovery inspired Freud’s belief that human sexual repression may be linked to our “usually atrophied” sense of smell.

Olfactory nerve

The olfactory nerve is the first (CN I) cranial nerve (TA: nervus olfactorius or nervus cranialis I) and is responsible for conveying the sense of smell from the nasal cavity to the brain. Strictly speaking, the term olfactory 'nerve' refers only to the short first order neurons (olfactory filaments) located on the olfactory mucosa. The olfactory bulb, tract and striae are often erroneously referred together as the olfactory nerve, but they are actually an extension of the central nervous system.

Some Women Without the Brain’s Olfactory Bulbs Can Still Smell. Scientists Say It Makes No Sense

Left-handed women missing the brain structures were still able to smell as well–or better—than average.

Tastebuds Suck! Long Live The Olfactory Bulb

More than anything, however, I now have even greater respect for all of our olfactory equipment, which, it seems, deserve a hell of a lot more credit for making life good. Because it turns out that a life with only tastebuds wouldn’t be much of a life at all.

The Dangers—and Surprising Pleasures—of Being Born Without Smell

A new study suggests COVID leaves 5 percent of people with persistent anosmia. I’ve had it my whole life.

The Olfactory Bulb: Function and Characteristics

Before we talk about the functions of the olfactory bulb, we should point out that although this part of the brain is responsible for capturing smells, the process doesn’t start there. Smells enter through the nostrils, are absorbed by the nasal mucosa, and information about the smells is processed by the neurons through sensory transduction. Then, that information passes through the olfactory nerve and reaches the olfactory bulb.

The Shape of the Olfactory Bulb Predicts Olfactory Function

The olfactory bulb (OB) plays a key role in the processing of olfactory information. A large body of research has shown that OB volumes correlate with olfactory function, which provides diagnostic and prognostic information in olfactory dysfunction. Still, the potential value of the OB shape remains unclear.

What are mitral cells?

The olfactory system begins in the olfactory epithelium, which lines the inside of our nasal passages. The primary cells associated with scent detection are the olfactory receptor neurons. They send their dendritic projections through the epithelium, where they can make contact directly with the air that passes through the nasal passage. These dendrites express odorant receptor proteins, which can detect chemicals in the air. The axons of these olfactory receptors project through tiny holes at the base of the skull called the cribriform plate.

Will My Sense Of Smell Ever Return? Olfactory Insights From COVID And Beyond

That depends on the cause. Nerves damaged by the pressure of swollen sinuses sometimes repair themselves, the evidence suggests, though my doctor says mine are unlikely to at this late date. Anti-inflammatory drugs, or surgery to remove swollen tissue or polyps, can help some people, maybe by allowing odorants to reach their receptors. And many smell and taste deficits caused by COVID-19 in the last year appear to be clearing up over time.

Resources

Odor2Action

The Odor2Action network brings together international scientists to solve classic, unresolved questions in neuroscience. Using the olfactory circuit, we aim to achieve an end-to-end understanding of how brains organize and process information from odors to guide adaptive behaviors. Through highly synergistic and inclusive team science, Odor2Action strives to create a model of open data and technology sharing that accelerates discoveries across the scientific community.