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How Does Scratching Relieve an Itch?

If you have an itch, you scratch it. Scratch and itch; they go together like peas and carrots and everyone—humans, apes, dogs and cats—knows it. What we didn't understand for a very long time was the physiological connection between the two—why a good scratch relieves a bad itch.

A study by a group of neuroscientists at the University of Minnesota recently explained the itch-scratch link.* The group hypothesized that the relief mechanism doesn't take place along the nerves of itchy skin, as had been thought, but deep in the central nervous system, in the same area that the itches themselves are communicated. Previous studies showed that neurons in the spinothalamic tract (STT)—a sensory pathway originating in the spinal cord that transmits information about pain, temperature and touch to the thalamus—were activated with the application of itch-inducing chemicals, and these are the neurons that send itch sensations to the brain.

In the new study, the UM researchers implanted recording electrodes in the spinothalmic tracts (STT) of macaques monkeys (the STT is at the base of the spinal cord; most STT neurons respond to pain and some to both pain and itch). Then researchers injected itch-inducing histamines into the monkeys' legs and watched as the STT neurons fired. They then scratched the monkey's itchy legs with a device that mimicked the feel of monkey fingers, and the firing rate of the STT neurons dropped rapidly.

The sudden drop, the researchers said, is the neurological equivalent of the relief you feel after a good scratch, indicating that itching and relief sensations are both rooted in the spinal cord and relief from an itch comes from inhibiting—via scratching—the STT neurons. Scratching basically tells all those tattle-tale neurons who are whining to the brain about an itch to just shut up already.

scratchingOf course, the itch and the scratch still hold plenty of mystery. When the team scratched the monkey's legs without first inducing an itch, the STT neurons fired in a normal response to stimuli, but the scratching didn't slow the firing.

Scratching also had no effect on neurons' response to an application of capsaicin, the spicy component in hot peppers. The STT neurons, it appears, react differently to the sensation of a scratch depending on whether an itch exists, and the nerve-dampening effect of scratching only works when the neurons are firing because of an itch, not pain. Somehow, the neurons know the difference. Itching isn't all physiological, either; it can be caused by emotional and psychological factors and can even be picked up as a "contagious itch" (a study showed that itching can be induced purely by visual stimuli: watching other people scratch).

Once all that is sussed out, though, the UM team's discovery could lead to ways of duplicating the end results and benefits of scratching (quiet, polite STT neurons) without its drawbacks. That's great news for people with the sorts of chronic itching associated with AIDS, Hodgkin's disease and the side effects of some pain medications. Chronic itching, of course, leads to plenty of scratching, which can lead to skin damage, infections and worse (remember the New Yorker article with the woman who scratched right through to her brain?)

* Davidson et al. Relief of itch by scratching: state-dependent inhibition of primate spinothalamic tract neurons. Nature Neuroscience, 2009; 12 (5): 544

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Interactive Chart Tells You How Long It Takes to Get Frostbite
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For many people, winter means dry skin and high heating bills. But if you find yourself outdoors in the right conditions, it can also mean frostbite. Frostbite occurs when the skin and the tissue beneath it freezes, causing pain, loss of sensation, or worse. It's easier to contract than you may think, even if you don't live in the Siberian tundra. To see if frostbite poses a threat where you live, check out this chart spotted by Digg.

The chart, developed by Pooja Gandhi and Adam Crahen using National Weather Service data, looks at three factors: wind speed, air temperature, and time spent outdoors. You can hover your cursor over data-points on the table to see how long you'd need to be exposed to certain wind chills for your skin tissue to freeze. If the wind chill is -22°F, for example (10°F air temperature with 5 mph winds), it would take 31 minutes of being outside before frostbite sets in. You can also look at the time scale above the chart to calculate it a different way. If you bring your cursor to the 40-minute mark, a window will tell that frostbite becomes a risk after exposure to -17°F wind chill for that amount of time. You can play with the interactive table at Tableau Public.

Chart of cold weather conditions.
Adam Crahen, Pooja Gandhi

If you can't avoid being outside in extreme wind and cold, there are a few steps you can take to keep your skin protected. Wear lots of layers, including multiple socks, and wrap your face with a scarf or face mask before venturing into the cold. Also, remember to stay hydrated. According to the American Academy of Dermatology, drinking at least one glass of water before going outside decreases your risk of contracting frostbite.

[h/t Digg]

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REM-Fit
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Stop Your Snoring and Track Your Sleep With a Wi-Fi Smart Pillow
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REM-Fit

Everyone could use a better night's rest. The CDC says that only 66 percent of American adults get as much sleep as they should, so if you're spending plenty of time in bed but mostly tossing and turning (or trying to block out your partner's snores), it may be time to smarten up your sleep accessories. As TechCrunch reports, the ZEEQ Smart Pillow improves your sleeping schedule in a multitude of ways, whether you're looking to quiet your snores or need a soothing lullaby to rock you to sleep.

After a successful Kickstarter in 2016, the product is now on sale and ready to get you snoozing. If you're a snorer, the pillow has a microphone designed to listen to the sound of your snores and softly vibrate so that you shift positions to a quieter pose. Accelerometers in the pillow let the sleep tracker know how much you're moving around at night, allowing it to record your sleep stages. Then, you can hook the pillow up to your Amazon Echo or Google Home so that you can have your favorite smart assistant read out the pillow's analysis of your sleep quality and snoring levels the next morning.

The pillow is also equipped with eight different wireless speakers that turn it into an extra-personal musical experience. You can listen to soothing music while you fall asleep, either connecting the pillow to your Spotify or Apple Music account on your phone via Bluetooth or using the built-in relaxation programs. You can even use it to listen to podcasts without disturbing your partner. You can set a timer to turn the music off after a certain period so you don't wake up in the middle of the night still listening to Serial.

And when it's time to wake up, the pillow will analyze your movements to wake you during your lightest sleep stage, again keeping the noise of an alarm from disturbing your partner.

The downside? Suddenly your pillow is just another device with a battery that needs to charge. And forget about using it in a place without Wi-Fi.

The ZEEQ Smart Pillow currently costs $200.

[h/t TechCrunch]

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