Posts Tagged ‘senses’
“Smell is a potent wizard that transports you across thousands of miles and all the years you have lived”*…
The most under-rated of our senses is also the least understood. But as Yasemin Saplakoglu reports, a better understanding of human smell is emerging as scientists interrogate its fundamental elements: the odor molecules that enter your nose and the individual neurons that translate them into perception in your brain…
… Smell is deeply tied with the emotion and memory centers of our brain. Lavender perfume might evoke memories of a close friend. A waft of cheap vodka, a relic of college days, might make you grimace. The smell of a certain laundry detergent, the same one your grandparents used, might bring tears to your eyes.
Smell is also our most ancient sense, tracing back billions of years to the first chemical-sensing cells. But scientists know little about it compared to other senses — vision and hearing in particular. That’s in part because smell has not been deemed critical to our survival; humans have been wrongly considered “bad smellers” for more than a century. It’s also not easy to study.
“It’s a highly dimensional sense,” said Valentina Parma, an olfactory researcher at the Monell Chemical Senses Center in Philadelphia. “We don’t know exactly how chemicals translate to perception.” But scientists are making progress toward systematically characterizing and quantifying what it means to smell by breaking the process down to its most fundamental elements — from the odor molecules that enter your nose to the individual neurons that process them in the brain.
Several new databases, including one recently published in the journal Scientific Data, are attempting to establish a shared scientific language for the perception of molecular scents — what individual molecules “smell like” to us. And on the other end of the pathway, researchers recently published a study in Nature describing how those scent molecules are translated into a neural language that triggers emotions and memories.
Together, these efforts are painting a richer picture of our strongest memory-teleportation device. This higher-resolution look is challenging the long-held assumption that smell is our least important sense…
[Saplakoglu recounts the history of our understanding of smell; explains the current science on how millions of molecules, often in complex bouquets, enter the nose and are processed by neurons to generate a sense of smell that’s deeply emotional and personal; and explores the ways in which it’s intstrumental in attraction, survival, and memory…]
… Because our sense of smell can be largely subliminal, in surveys many people, given the choice of losing one sense, choose olfaction. But “every day, I experience people sitting in my office and talking about how they are disconnected to the world,” [Thomas] Hummel said. They can’t smell their children or spouses anymore. They cannot detect bad-smelling food or dangerous smoke. They no longer have access to certain memories.
“I know the memory is there, but I don’t have the key to open [it] anymore,” Hummel said. “Life becomes a much more insecure place without a sense of smell in many ways, but you only realize it when it’s gone.”…
Fascinating: “How Smell Guides Our Inner World,” from @yaseminsaplakoglu.bsky.social in @quantamagazine.bsky.social.
* Helen Keller
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As we get to know the nose, we might celebrate the avatar of affecting aromas: today is National Cheese Pizza Day.
“Touch has a memory”*…
… and, as Ariel Bleicher explains in her report on the work of neurobiologst David Ginty, so much more…
Like many proud parents, David Ginty (opens a new tab) has decorated his office with pictures of his genetic creations. There’s the prickly one sporting a spiked collar and the wannabe cowboy twirling a lasso. There’s the dramatic one, always reacting to the slightest provocation; the observant one that notices every detail; the golden child Ginty loves to boast about. “They’re like a family,” he said. “Each one has its own quirks and individual characteristics.”
They’re not really a family and, anyway, they’re not his children. They have evolved over millions of years to give humans and other mammals an interface with the physical world around us. But Ginty, who heads the neurobiology department at Harvard Medical School, has been studying this quirky cast of characters — the sensory neurons of touch — for more than two decades, and has gotten to know them better than anyone else ever has. He has learned their electrical language and what forces excite them, and charted their intricate paths into the skin and up to the brain. And, through feats of genetic engineering and chemical labeling, he has produced the colorful portraits on his walls.
“David Ginty is the emperor of touch,” said Alexander Chesler, a sensory neuroscientist at the National Institutes of Health…
… Beyond the technical breakthroughs and the discoveries fit for biology textbooks, it’s the images that stick in his colleagues’ minds. They’re otherworldly, like deep-sea creatures — not at all what you might imagine neurons could look like. These strangely shaped cells are the reason why the experience of touch is so rich and multifaceted — why a buzzing cell phone feels different from a warm breeze or a lover’s caress, from raindrops or a mother’s kiss. To realize that your body is covered in them — that they are a part of you — takes your breath away.
“Each one of these neurons tells a story,” Ginty said. “Each one has a structure that is unique and responds to different things. It’s all about form underlying function. That’s where the beauty is.”
Scientists and philosophers have been enamored with touch for centuries. Aristotle believed that humans’ tactile abilities eclipsed those of all other species, which partially accounted for our superior intelligence. However, we now know that creatures as diverse as sea lions, spiders and star-nosed moles can feel features of the physical world that are imperceptible to us. Yet Aristotle wasn’t wrong to view touch as exceptional.
Of all the senses, the somatosensory system is the most complex, and therefore touch, some researchers argue, is the most difficult to study. Vision and hearing, for instance, are confined to the retina and the cochlea — parts the size of a postage stamp and a pea, respectively. Touch, however, is diffuse: The neurons that relay touch signals reside in clusters outside the spinal cord, from which they extend a vast web of axon fibers, like jellyfish tentacles, into the skin and internal organs. Each axon forms an ending just beneath the skin’s surface; the different types of endings are mechanisms for picking up and interpreting the variety of touch sensations.
While our eyes and ears each process information related to light or sound, touch concerns a smorgasbord of stimuli, including pokes, pulls, puffs, caresses and vibrations, as well as a range of temperatures and chemicals, such as capsaicin in chili peppers or menthol in mint. From these inputs arise perceptions of pressure, pain, itchiness, softness and hardness, warmth and cold, and the awareness of the body in space.
But how?…
[Bleicher recounts the history of exploration of touch, and unpacks Ginty’s pioneering work…]
… Over the past five years, Ginty and other scientists have analyzed the genetics of thousands of individual touch neurons. Sorting these cells according to the genes they express, Ginty’s team has so far come up with 18 distinct types, maybe more — it’s hard to tell, given the limited resolution of their sorting tools. That total includes the six or seven gentle-touch neurons on which Ginty’s research has primarily focused, as well as six neurons for stronger mechanical stimuli (some of which also respond to temperature and chemical irritants), one neuron for painful heat, one for cold, three or more for sensing body position, and a few whose functions are unknown.
As more touch neurons are analyzed, the count will likely increase. And each genetically distinct type can be further subdivided based on its axon endings. Genetically identical neurons that form Meissner corpuscles for picking up vibrations in glabrous skin, for example, also form lanceolate endings for detecting hair movement in hairy skin. In a 2023 study, Ginty’s team showed that these same touch neurons also innervate the colon, where their axons branch and curl around motor neurons in the gut, enabling us to sense bowel distention. “So you might say there are actually 50 or 60 different touch neuron types,” he said, if you count both genetic and physical variations. “We don’t know how many there are.”
Ginty will keep counting them. Today he’s asking the same fundamental questions he set out to answer more than a decade ago: Where do the various touch neurons go, what are their end structures, and how do they capture the richness of the physical realm? “We’ve gotten a pretty good handle on who’s who in the skin and what their response properties are,” Ginty said. But what about the heart, lungs, larynx, esophagus, stomach, intestines and kidneys? What are the neurons that make muscles ache and fatigue, or trigger migraines, or cause milk to flow in a mother’s breast when her baby suckles?
Ginty also wants to know how all these neurons connect to the brain to generate perceptions. How does pressure and vibration across millions of nerve endings become a hug? How do we feel wetness, slipperiness or elasticity? “Think about squeezing a balloon,” he said. “Presumably no one sensory neuron type is going to encode squeeziness.”…
Cataloging the neurons beneath everyday sensations: “Touch, Our Most Complex Sense, Is a Landscape of Cellular Sensors,” from @quantamagazine.bsky.social.
* John Keats
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As we celebrate the senses, we might recall that on this date in 1927 a sensory expert in a different domain, Mae West, was sentenced to jail for obscenity.
Her first starring role on Broadway was in a 1926 play entitled Sex, which she wrote, produced, and directed. Although conservative critics panned the show, ticket sales were strong. The production did not go over well with city officials, who had received complaints from some religious groups, and the theater was raided and West arrested along with the cast. She was taken to the Jefferson Market Court House (now Jefferson Market Library), where she was prosecuted on morals charges, and on April 19, 1927, was sentenced to 10 days for “corrupting the morals of youth.” Though West could have paid a fine and been let off, she chose the jail sentence for the publicity it would garner. While incarcerated on Welfare Island (now known as Roosevelt Island), she dined with the warden and his wife; she told reporters that she had worn her silk panties while serving time, in lieu of the “burlap” the other girls had to wear. West got great mileage from this jail stint. She served eight days with two days off for “good behavior”.
Wikipedia
“No one ever explained the octopuses”*…
We humans are forward-facing, gravity-bound plodders. David Borkenhagen wonders if the liquid motion of the octopus can radicalize our ideas about time…
… The octopus may navigate its ocean home with ease, but it can seem like a creature from another planet. It populates our popular visions of cosmic beings and extraterrestrial life, with its eight arms, three hearts, and a malleable body without bones. What’s more, its ability to camouflage itself, coupled with a propensity to hide in tight holes, make it a master of disguise. If seen, a water siphon that expels inhaled water can instantly propel the creature away from danger in any direction in three-dimensional aquatic space. Its web of radially symmetrical arms allow it to crawl in any direction with equal competence, regardless of how its head is oriented. Its soft and malleable body can move through any crevasse larger than its beak. And with its two eyes positioned on opposite sides of its head, it has a near-total field of vision with almost nothing hidden ‘behind’. These abilities give the octopus a radically different relationship to its surroundings compared with other species, human or otherwise. It is a relationship free of constraints.
And what about our bodies? Compared with the octopus, human beings appear corporeally constrained. We lack the fluid mobility and wide field of vision of our (very, very) distant cephalopod cousins. Instead, we have two eyes stuck in the front of our heads. We have a paltry two legs, hardwired for forward movement. And we are bound to our terrestrial ecological niche, where our bodies must continually counteract the downward pull of gravity.
It’s not only that our experiences of space are different. Our experiences of time are likely different, too. We think about the passage of time through our terrestrial experience of unidirectional motion through space – our metaphors of time are almost all grounded in the way our bodies move forward through the environment. Given this fact, how would an octopus, who can easily see and move in all directions, conceptualise time? Current research methods may be able to take us only part of the way toward an answer, but it’s far enough to consider a radical possibility: if we became more like an octopus, could we free time, metaphorically speaking, from its constraints? Could we experience it as multidimensional, fluid and free?…
[Borkenhagen reviews the research on octopuses and what it tells us about how their relationships with time and death]
… In many ways, the octopus represents a challenge, or a profound limit, to our conventional ways of thinking about time and death. But it’s more than a challenge. It’s also an invitation. With its unconstrained movements and semelparous lifecycle, the octopus offers a radically different perspective on the fluidity and flexibility of existence. Could we learn to move through time as an octopus moves through space? With equal access to the past, present and future – viewed wide or with sharp focus – we might better navigate the challenges of living and dying on Earth. The octopus invites us to think in a way that dissolves the boundaries between the present and the future, understanding our ‘ending’ less as a fixed point and more as a fluid process stretching across generations. As the boundary between life and death dissolves and becomes more porous, so do the boundaries between ourselves and others. The metaphors we used to inhabit our time here may seem impoverished, but there’s another way. It’s in the unconstrained movements of an octopus traveling through space – fluid, flexible and free…
“Octopus Time,” from @posts_modern in @aeonmag. Eminently worth reading in full.
Pair with The Mountain in the Sea by Ray Nayler and/or “Stories of Your Life” in the short story collection of the same title, by Ted Chiang
* Gail Garriger (@gailcarriger)
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As we re-understand unfolding, we might recall that it was on this date in 1871 that the American Museum of Natural History opened to the public in New York City. Organized into a series of exhibits, the Museum’s collection–which had been gathered from the time of the Museum’s founding in 1869– went on view for the first time in the Central Park Arsenal, the Museum’s original home, on the eastern side of Central Park. The cornerstone of the Museum’s first building was laid in Manhattan Square (79th Street and Central Park West), the Museum’s current location, in 1874; but it is obscured from view by the many Museum buildings in the complex that today occupy most of the Square.
“Smells are the fallen angels of the senses”*…
In an excerpt from his new book, Where We Meet the World: The Story of the Senses, Ashley Ward contemplates the oft-ignored and much-maligned olfactory sense…
Despite the wonderful contributions that smell makes to our lives, it’s undervalued in modern Western societies. Polls conducted in both the US and the UK reported that of our five main senses, smell was the one that people were least concerned about losing, while a study of British teenagers found that half would rather be without their sense of smell than their phone.
Despite the wonderful contributions that smell makes to our lives, it’s undervalued in modern Western societies. Polls conducted in both the US and the UK reported that of our five main senses, smell was the one that people were least concerned about losing, while a study of British teenagers found that half would rather be without their sense of smell than their phone.
It may have to do with olfaction’s checkered past. For much of human history, smells were things to be wary of. The idea that sickness was borne out of noxious smells was the prominent theory in disease propagation for centuries. Clouds of pungency, known as miasmas, released from unclean dwellings, filthy streets, and even the ploughing of soil, were blamed for contaminating the body, leading to any number of maladies. A debilitating fever emerging from marshes and swamps was named after the medieval Italian for bad air: mal’aria. Terrifying epidemics that haunted the world for centuries seemed to be induced by foul, corrupted air.
…
While odors themselves were regarded with distrust, it seems like every famous man in history who ever felt moved to write about our sense of smell had some derogatory point to make (there’s a notable shortage of opinions from the women of history). Most fall into one of two camps: those who regarded smell as relatively unimportant, and those who associated it with depravity. Plato considered that smell was linked to “base urges,” while others described it as degenerate and animalistic. Aristotle wrote that “man smells poorly” and Darwin asserted that “the sense of smell is of extremely slight service.”
…
The migration of primate eyes to the front of the face allows excellent stereoscopic vision, compared to the side-of-the-head arrangement favored by many other mammals, but limits the space available for the olfactory equipment. The loss of the snout in apes especially seems only to further restrict the capacity for smell.
Finally, primates in general and humans in particular seem to be losing genes associated with our sense of smell. We have something like 400 working olfactory genes, but sitting in our genetic code are close to 500 olfactory pseudogenes. These are the genetic equivalents of fossils; genes that used to contribute to our sense of smell but that no longer work. In other words, we’ve lost over half of our smell genes across evolutionary time…
Eminently worth reading in full: “How Smell—the Most Underrated Sense—Was Overpowered By Our Other Senses,” from @ashleyjwward in @lithub.
* Helen Keller
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As we breathe in, we might we might recall that it was on this date in 1943 that Swiss chemist Albert Hofmann discovered the sensory- enhancing, even altering– that’s to say, psychedelic– properties of LSD. Hofmann had synthesized the drug five years earlier, but its hoped-for use in treating respiratory problems didn’t pan out, and it was shelved. On this day, he accidentally absorbed some of the drug through his skin (as he touched its container). He became dizzy with hallucinations. Three days later he took the first intentional dose of acid: 0.25 milligrams (250 micrograms), an amount he predicted to be a threshold dose (an actual threshold dose is 20 micrograms). Less than an hour later, Hofmann experienced sudden and intense changes in perception. He asked his laboratory assistant to escort him home and, as use of motor vehicles was prohibited because of wartime restrictions, they had to make the journey on a bicycle… which is why April 19 has been celebrated (since 1985) as “Bicycle Day.”
“The sound must seem an echo to the sense”*…
As devices once common fall out of use, we stop hearing the sounds that they made…
“Conserve the sound” is an online archive for disappearing sounds. The sounds of a rotary dial phone, a Walkman, an analog typewriter, a pay phone, a 56k modem, a nuclear power plant or even a mobile phone keyboard have partly disappeared or are just disappearing from everyday life. In addition, people have their say in text and video interviews and deepen their view into the world of disappearing sounds…”
The signature sounds of the items above and so many more: “Conserve the sound,” a project of CHUNDERKSEN.
Apposite: “Google Translate for the zoo? How humans might talk to animals,” a review of Karen Bakker‘s The Sounds of Life.
And. of course, 32 Sounds.
* Alexander Pope
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As we listen in, we might recall that it was on this date in 1986, in Cleveland, that the Rock and Roll Hall of Fame inducted it’s first class of members: Little Richard, Chuck Berry, James Brown, Ray Charles, Sam Cooke, Fats Domino, The Everly Brothers, Alan Freed, John Hammond, Buddy Holly, Robert Johnson, Jerry Lee Lewis, San Phillips, Elvis Presley, Little Richard, Jimmie Rodgers, and Jimmy Yancey. The I. M. Pei designed museum opened on June 7, 1993.
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