Tag Archives: sense

Technica

The Joy of New Technology

prosthetic-hand

We are makers. We humans love to create and invent. Some of our inventions are hideous, laughable or just plain evil — Twinkies, collateralized debt obligations and subprime mortgages, Agent Orange, hair extensions, spray-on tans, cluster bombs, diet water.

However, for every misguided invention comes something truly great. This time, a prosthetic hand that provides a sense of real feeling, courtesy of the makers of the Veterans Affairs Medical Center in Cleveland, Ohio.

From Technology Review:

Igor Spetic’s hand was in a fist when it was severed by a forging hammer three years ago as he made an aluminum jet part at his job. For months afterward, he felt a phantom limb still clenched and throbbing with pain. “Some days it felt just like it did when it got injured,” he recalls.

He soon got a prosthesis. But for amputees like Spetic, these are more tools than limbs. Because the prosthetics can’t convey sensations, people wearing them can’t feel when they have dropped or crushed something.Now Spetic, 48, is getting some of his sensation back through electrodes that have been wired to residual nerves in his arm. Spetic is one of two people in an early trial that takes him from his home in Madison, Ohio, to the Cleveland Veterans Affairs Medical Center. In a basement lab, his prosthetic hand is rigged with force sensors that are plugged into 20 wires protruding from his upper right arm. These lead to three surgically implanted interfaces, seven millimeters long, with as many as eight electrodes apiece encased in a polymer, that surround three major nerves in Spetic’s forearm.

On a table, a nondescript white box of custom electronics does a crucial job: translating information from the sensors on Spetic’s prosthesis into a series of electrical pulses that the interfaces can translate into sensations. This technology “is 20 years in the making,” says the trial’s leader, Dustin Tyler, a professor of biomedical engineering at Case Western Reserve University and an expert in neural interfaces.

As of February, the implants had been in place and performing well in tests for more than a year and a half. Tyler’s group, drawing on years of neuroscience research on the signaling mechanisms that underlie sensation, has developed a library of patterns of electrical pulses to send to the arm nerves, varied in strength and timing. Spetic says that these different stimulus patterns produce distinct and realistic feelings in 20 spots on his prosthetic hand and fingers. The sensations include pressing on a ball bearing, pressing on the tip of a pen, brushing against a cotton ball, and touching sandpaper, he says. A surprising side effect: on the first day of tests, Spetic says, his phantom fist felt open, and after several months the phantom pain was “95 percent gone.”

On this day, Spetic faces a simple challenge: seeing whether he can feel a foam block. He dons a blindfold and noise-­canceling headphones (to make sure he’s relying only on his sense of touch), and then a postdoc holds the block inside his wide-open prosthetic hand and taps him on the shoulder. Spetic closes his prosthesis—a task made possible by existing commercial interfaces to residual arm muscles—and reports the moment he touches the block: success.

Read the entire article here.

Image: Prosthetic hand. Courtesy of MIT Technology Review / Veterans Affairs Medical Center.

BigBang

Hearing and Listening

Auditory neuroscientist Seth Horowitz guides us through the science of hearing and listening in his new book, “The Universal Sense: How Hearing Shapes the Mind.” He clarifies the important distinction between attentive listening with the mind and the more passive act of hearing, and laments the many modern distractions that threaten our ability to listen effectively.

[div class=attrib]From the New York Times:[end-div]

HERE’S a trick question. What do you hear right now?

If your home is like mine, you hear the humming sound of a printer, the low throbbing of traffic from the nearby highway and the clatter of plastic followed by the muffled impact of paws landing on linoleum — meaning that the cat has once again tried to open the catnip container atop the fridge and succeeded only in knocking it to the kitchen floor.

The slight trick in the question is that, by asking you what you were hearing, I prompted your brain to take control of the sensory experience — and made you listen rather than just hear. That, in effect, is what happens when an event jumps out of the background enough to be perceived consciously rather than just being part of your auditory surroundings. The difference between the sense of hearing and the skill of listening is attention.

Hearing is a vastly underrated sense. We tend to think of the world as a place that we see, interacting with things and people based on how they look. Studies have shown that conscious thought takes place at about the same rate as visual recognition, requiring a significant fraction of a second per event. But hearing is a quantitatively faster sense. While it might take you a full second to notice something out of the corner of your eye, turn your head toward it, recognize it and respond to it, the same reaction to a new or sudden sound happens at least 10 times as fast.

This is because hearing has evolved as our alarm system — it operates out of line of sight and works even while you are asleep. And because there is no place in the universe that is totally silent, your auditory system has evolved a complex and automatic “volume control,” fine-tuned by development and experience, to keep most sounds off your cognitive radar unless they might be of use as a signal that something dangerous or wonderful is somewhere within the kilometer or so that your ears can detect.

This is where attention kicks in.

Attention is not some monolithic brain process. There are different types of attention, and they use different parts of the brain. The sudden loud noise that makes you jump activates the simplest type: the startle. A chain of five neurons from your ears to your spine takes that noise and converts it into a defensive response in a mere tenth of a second — elevating your heart rate, hunching your shoulders and making you cast around to see if whatever you heard is going to pounce and eat you. This simplest form of attention requires almost no brains at all and has been observed in every studied vertebrate.

More complex attention kicks in when you hear your name called from across a room or hear an unexpected birdcall from inside a subway station. This stimulus-directed attention is controlled by pathways through the temporoparietal and inferior frontal cortex regions, mostly in the right hemisphere — areas that process the raw, sensory input, but don’t concern themselves with what you should make of that sound. (Neuroscientists call this a “bottom-up” response.)

But when you actually pay attention to something you’re listening to, whether it is your favorite song or the cat meowing at dinnertime, a separate “top-down” pathway comes into play. Here, the signals are conveyed through a dorsal pathway in your cortex, part of the brain that does more computation, which lets you actively focus on what you’re hearing and tune out sights and sounds that aren’t as immediately important.

In this case, your brain works like a set of noise-suppressing headphones, with the bottom-up pathways acting as a switch to interrupt if something more urgent — say, an airplane engine dropping through your bathroom ceiling — grabs your attention.

Hearing, in short, is easy. You and every other vertebrate that hasn’t suffered some genetic, developmental or environmental accident have been doing it for hundreds of millions of years. It’s your life line, your alarm system, your way to escape danger and pass on your genes. But listening, really listening, is hard when potential distractions are leaping into your ears every fifty-thousandth of a second — and pathways in your brain are just waiting to interrupt your focus to warn you of any potential dangers.

Listening is a skill that we’re in danger of losing in a world of digital distraction and information overload.

[div class=attrib]Read the entire article following the jump.[end-div]

[div class=attrib]Image: The Listener (TV series). Courtesy of Shaftsbury Films, CTV / Wikipedia.[end-div]

Idea Soup

The Ascent of Scent

Scents are deeply evokative. A faint whiff of a distinct and rare scent can bring back a long forgotten memory and make it vivid, and do so like no other sense. Smells can make our stomachs churn and make us swoon.

The scent-making industry has been with us for thousands of years. In 2005, archeologists discovered the remains of a perfume factory on the island of Cyprus dating back over 4,000 years. So, it’s no surprise that makers of fragrances, from artificial aromas for foods to complex nasal “notes” for perfumes and deodorants, now comprise a multi-billion dollar global industry. Krystal D’Costa over at Anthropology in Practice takes us on a fine aromatic tour, and concludes her article with a view to which most can surely relate:

My perfume definitely makes me feel better. It wraps me in a protective cocoon that prepares me to face just about any situation. Hopefully, when others encounter a trace of it, they think of me in my most confident and warmest form.

A related article in the Independent describes how an increasing number of retailers are experimenting with scents to entice shoppers to linger and spend more time and money in their stores. We learn that

. . . a study run by Nike showed that adding scents to their stores increased intent to purchase by 80 per cent, while in another experiment at a petrol station with a mini-mart attached to it, pumping around the smell of coffee saw purchases of the drink increase by 300 per cent.

[div class=attrib]More from Anthropology in Practice:[end-div]

At seventeen I discovered the perfume that would become my signature scent. It’s a warm, rich, inviting fragrance that reminds me (and hopefully others) of a rose garden in full bloom. Despite this fullness, it’s light enough to wear all day and it’s been in the background of many of my life experiences. It announces me: the trace that lingers in my wake leaves a subtle reminder of my presence. And I can’t deny that it makes me feel a certain way: as though I could conquer the world. (Perhaps one day, when I do conquer the world, that will be the quirk my biographers note: that I had a bottle of X in my bag at all times.)

Our world is awash in smells—everything has an odor. Some are pleasant, like flowers or baked goods, and some are unpleasant, like exhaust fumes or sweaty socks—and they’re all a subjective experience: The odors that one person finds intoxicating may not have the same effect on another. (Hermione Granger’s fondness for toothpaste is fantastic example of the personal relationship we can have with the smells that permeate our world.)  Nonetheless, they constitute a very important part of our experiences. We use them to make judgments about our environments (and each other), they can trigger memories, and even influence behaviors.

No odors seem to concern us more than our own, however. But you don’t have to take my word for it—the numbers speak for themselves: In 2010, people around the world spent the equivalent of $2.2 billion USD on fragrances, making the sale of essential oils and aroma chemicals a booming business. The history of aromatics sketches our attempts to control and manipulate scents— socially and chemically—illustrating how we’ve carefully constructed the smells in our lives.

[div class=attrib]More from theSource here.[end-div]

[div class=attrib]Image: The Perfume Maker by Ernst, Rodolphe, courtesy of Wikipedia / Creative Commons.[end-div]