Smell, Touch, and Taste

Smell, explained

Humans may be able to distinguish between more than a trillion different odors—extending our awareness beyond our immediate surroundings to enable us to detect gas leaks or pick up the scent of someone who just left the room. Smell is one of our most powerful senses. It's better than sight at evoking strong memories because of the anatomy of the olfactory system, which allows neural signals about smell to bypass an area of the brain called the thalamus so that the olfactory bulb in the forebrain connects directly to brain areas that manage emotion and memory. 

When we smell something, we are actually breathing in tiny molecules that stimulate specialized olfactory neurons high inside the nose. Our olfactory system allows us to detect and discriminate between these substances, and our brain assigns these scents an emotional tag that influences our thoughts and actions—eat this, avoid this, flee. 

The anatomy of the nose and throat makes it possible to decipher complex flavor profiles because chemicals from the foods we eat travel from our mouths and throat to the olfactory neurons high inside the nose. Then, the brain attaches labels to those scents, just as it does with scents from the external environment.

Partial or total loss of the sense of smell—hyposmia and anosmia, respectively—can significantly impact quality of life, and typically occurs due to disease or trauma. Anosmia occurs among roughly 3% of the US adult population over age 40. Sometimes this issue resolves on its own, but steroids and long-term smell retraining can often help. Phantom odor perception—smelling odors that aren't actually present—occurs in roughly 7% of Americans over the age of 40.

Explore everything else we've found on Smell.

Also, check out ... 

> A stand-in "nose" may help people with anosmia to smell certain odors. (Read) 

> Scientists are reconstructing the smell of an ancient Egyptian mummy. (Watch)

> A "fishy" scent does lead to mistrust. (Read) 

> A dog's central sniffing organ is many times bigger than a human's. (Watch)

The importance of taste buds

Taste buds do more than let you experience your favorite food. These peripheral organs can sense the chemical makeup, potential toxicity, and fleeting experience of flavor, giving the body a chance to respond to undesirable chemicals or tell the brain that you should reach for another scoop.

A mammal's tongue is covered in four types of small bumps known as papillae, three of which detect taste and at least one of which detects texture, temperature, and pain. These papillae—circumvallate, fungiform, and foliate—each have several taste buds, which are garlic-shaped structures made up of 50 to 100 chemosensory taste cells.

Each taste cell contains receptors for certain tastes, of which there are officially five: sweet, sour, salty, bitter, and umami (though more may exist, and recent research has posited that "fat" and "ammonium" are among the candidates).

Explore everything else we've found on Taste Buds.

Also, check out ... 

> How the methods of catching fish for food affect their taste. (Watch)

> Octopuses have taste receptors along their tentacles. (Watch) 

> The idea of a tongue map has been discredited (but taste sensitivity varies across the tongue). (Read)

> Cats have a mutation preventing them from tasting sugar. (Read)

Touch 101 

Touch is an essential part of the human experience, used to establish connections and convey support, affection, sympathy, reassurance, and love. Research has provided scientific backing for the idea that consensual touch provides numerous health benefits through every stage of life. 

Humans' relationship with touch begins early: It's the first sense to develop during gestation, at around eight weeks. When we perceive touch, that information is first sent to the thalamus and then onward to the primary somatosensory cortex, which encodes the physical properties of touch. Touch also activates the brain's orbitofrontal cortex—the area of the brain associated with feelings of reward, compassion, and impulse control—which helps us determine whether the touch was pleasant or unpleasant and gauge how to respond.

The identity of the toucher matters for newborns, with the greatest soothing benefit coming from a parental touch. But touch studies suggest that—for adults—the frequency of consensual touch matters more than who is doing the touching. Even nonhuman forms of touch, like experiencing a weighted blanket, or perhaps eventually robotic touch, could hold promise.

Explore everything else we've found on Touch.

Also, check out ... 

> A researcher thinks she knows why people keep touching museum exhibits. (Read)

> Generally, NBA basketball teams whose players touch each other more win more games. (Read)

> Why can't humans tickle themselves? (Read)

> Car touchscreen debuted on 1986 Buick Riviera, but flopped. (Read)

 Medical Developments Spotlight 

We love spending time learning about the latest medical breakthroughs and spotlighting research that piques our interest, may influence future research directions, or inform healthcare conversations. Here's what we found this week.

> It's not just an urban legend—your tongue can get stuck to frozen metal

IFLScience | James Felton. Norwegian researchers scoured published accounts and found more than 100 unique cases of "tundra tongue" reported in Scandinavian newspapers since the first known incident in 1845. Sixty percent of the incidents occurred among boys, and in 18% of all the cases, lickers had to get the flesh of their tongue ripped away. The scientists also conducted experiments with dozens of pig tongues and cold lampposts—identifying which temperatures were most likely to require painful detachment. (Read) 

> The little-known thymus may be more important for adult health than we knew

Harvard Medical School | Staff. A pair of studies found that when this tiny organ in the chest is healthy, it's linked to increased longevity and reduced risk of cardiovascular disease and cancer for as-yet unknown reasons. Until now, the thymus has been best known for training T cells to establish immune function in childhood and then shrinking as we age. The new conclusions were based on AI analysis of routine CT scans, separate analysis of CT scans from immunotherapy-treated patients, and thymus health assessments. (Read) 

> A huge study of weed as a mental health aide says evidence is sparse
NPR | Will Stone. The analysis of 45 years' worth of data, including 54 studies on cannabis use and potential benefits for mental health, came up short on evidence for helping treat the symptoms of anxiety, post-traumatic stress disorder, and depression—common reasons people turn to the stuff. Researchers say this means more well-designed studies are needed and caution that specific compounds may show promise. (Read) 

Best of the Week

We curate hundreds of resources into 1440 Topics each week. Here are some of our favorites from the world of health and medicine.

> That time a woman sneezed out maggots.

> The mental fatigue of AI 'brain fry' at work—and what managers can do about it. 

> Strategies for how to deal with other people's big feelings. 

> Neanderthals may have used tree bark as an antibiotic.

> Adults with ADHD experience sleep-like brain waves—while awake.

> Sewage is backing up in US basements.

> Cosmetic surgery companies are booming with little regulatory oversight.

> Who is doing the caregiving in America for aging parents and partners?

> Air pollution in war-torn Iran unleashes invisible toxic threats.

> Influencers' supplement regimens are costing over $1,000 per month.

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