Sensory Receptors in the Skin

[Iniko Ujaama]

http://www.pbs.org/wgbh/nova/next/body/skin-can-smell/


When Your Skin Smells Sandalwood Oil, It Heals Itself

Your nose isn’t the only part of your body capable of taking a whiff.

In the past decade, scientists have discovered olfactory receptors lingering in strange places—in sperm, in the spine, and even in the kidneys. Now researchers in Hanns Hatt’s lab at Germany’s Ruhr University Bochum have identified scent receptors somewhere much more accessible: the skin. What’s more, these receptors appear to be involved in healing.


Sandalore, a synthetic sandalwood oil, binds to an olfactory receptor in the skin, prompting the healing process.

Here’s Bob Roeher, writing for New Scientist:

    They found that Sandalore—a synthetic sandalwood oil used in aromatherapy, perfumes and skin care products—bound to an olfactory receptor in skin called OR2AT4. Rather than sending a message to the brain, as nose receptors do, the receptor triggered cells to divide and migrate, important processes in repairing damaged skin.

    Cell proliferation increased by 32 per cent and cell migration by nearly half when keratinocytes [skin cells] in a test tube and in culture were mixed for five days with Sandalore.

In other words, your skin has the ability to smell, just not in the way we normally think of. Instead, certain odorants target “smelling” receptors in the skin, which prompt the healing process. Of course, just as one nose is different from another, so are the scent receptors in our skin. One person’s genetics might predispose them to greater olfactory sensitivity than another’s.

This discovery is another example of our skin’s unexpected abilities. This week, NOVA Next contributor Sujata Gupta reported on the skin’s ability to “hear” sound. And new findings about our sense of touch, too, have illuminated a possible sensory-social dimension of autism. In the future, we might see a growing number of treatments channeled through the skin, whether they are topical solutions or otherwise.

[Iniko Ujaama]

Music for Your Skin

I settle into an orange camp chair that has been stripped and fitted with 16 small, round voice coils, or speakers without loudspeaker cones. Carmen Branje hands me a pair of noise canceling headphones connected to his smartphone and launches a white noise app with instructions to jack up the volume as high as possible. Soon I feel as if I’m underneath a rushing waterfall. Branje hits play on a nearby computer and the chair begins to vibrate, though I can no longer hear the whir. The beat plays fast across my skin, the buzzes fluctuating from soft to intense as they flit up and down my back.

After a few minutes, the buzzing stops and I remove the headphones. Happy or sad? Branje asks. Happy, I respond. Definitely happy.

Audio-visual technologies have long dominated the media landscape, but touch-based, or haptic, technologies, could soon become more than a novelty. As far back as the 1950s, renowned psychologist and tactile researcher Frank Geldard noted that our narrow focus on the ears and eyes ignored other perfectly good channels of communication. The skin, he wrote in 1960, “is a good break-in sense: cutaneous sensations, especially if aroused in unusual patterns, are highly attention-demanding.”

Nowadays, with so many gadgets clamoring for the attention of our ears and eyes, using the skin as an alert system has started to gain traction. Cell phones buzz. The handheld controller in Wii vibrates when a user knocks out his opponent in a mock boxing match. General Motors recently installed vibrators inside the seats of its luxury cars to alert drivers when somebody enters their blind spot or when they’re drifting too far to one side. Researchers are looking at placing touch sensors along the body to improve bowing technique on the violin, facilitate rehabilitation after an injury or stroke, allow coaches to direct players on the field without yelling, and even help astronauts stay oriented in space.

But here, at the glass-walled Inclusive Media and Design Centre at Ryerson University in Toronto, Canada, the goals are loftier. Branje, who was a week shy of defending his doctoral thesis when I visited, believes our sense of touch can do a lot more than receive alerts. Cell phones vibrate at a single frequency, and so does the buzzer under one’s butt in a Cadillac. But Branje, himself a musician, thinks touch can be used to mimic an octave or the feel of a melancholic song. Someday, he says, maybe we’ll have a new genre of “music” based not on sound but touch. “Instead of an mp3,” he says, “I would send you a vib [vibrational] file.”

Hearing Speech Through Skin

Nobel laureate Georg von Békésy, a biophysicist at Harvard University, frequently lamented that those studying hearing, like himself, rarely researched the skin. Békésy’s research, inspired by his desire to understand difficult to access parts of the ear via the skin, showed that acoustic elements like pitch, loudness, and rhythm all had touch-based equivalents.

Anatomy backs up his discoveries. The skin is underlain with four mechanoreceptors that each respond to different forms of touch, such as a light tap, pressure, or pain. But in the 1980s, researchers found that those same receptors could respond to—or “hear”—different frequencies. Compared with the tens of thousands of mechanoreceptors in our ears, known as hair cells, the resolution of the tactile system is terrible. But their existence illustrates striking similarities between the two systems.

Much of our early understanding of the skin’s ability to receive sound comes from a line of research that blossomed in the 1970s and ’80s: enabling deaf people to “hear” the vibrational patterns that make up speech through their skin. That idea first emerged at a deaf school in the 1920s, says Janet Weisenberger, a psychologist at Ohio State University in Columbus, and an early researcher in the field. At that time, researchers essentially affixed miniature loudspeakers to user’s hands and fingers, but because the skin can’t feel anything above 1,000 hertz—which is where we distinguish among different vowels and consonants—users were able to detect that someone was speaking, but not comprehend what was being said.

Weisenberger and her team have studied a 16-vibrator device that could circumvent the skin’s frequency limitations by utilizing its abundant surface area. For instance, Weisenberger arrayed the device across users’ arms. A high-frequency note like the sound of the letter “s” would buzz near the elbow while a lower frequency note like “oo” would buzz near the wrist. The name Sue would thus vibrate in quick succession at the elbow followed by the wrist. In that way, people could be trained to recognize the patterns that went along with different vowels and consonants, Weisenberger says. The device “transformed frequency into location.”

That finding, coupled with others such as helping users distinguish between words that appear identical on the lips (look in a mirror and say pat and bat) significantly improved the accuracy of lipreading, which alone enables a user to understand a frustratingly low 30–60% of a conversation.

But before the device could reach prime time, another technology soon upended that work. Cochlear implants, which rose to prominence in the early 1990s, reroute sound from the damaged hair cells in the inner ear directly to the auditory nerve. Today, deaf individuals with cochlear implants have greater access to speech and sound than ever before. Funding and interest in haptic speech soon dried up. Yet the information gleaned from that work could serve another purpose—giving the deaf greater access to music.


A closer look at the voice coils on the Emoti-Chair


Branje's custom keyboard activates the voice coils on the Emoti-Chair.



full article: http://www.pbs.org/wgbh/nova/next/body/haptic-hearing/

[Iniko Ujaama]

Touch is the first sensory system to develop in babies, and for good reason. Physical connection is vital to our social and cognitive development, especially in infancy. Of course, its importance continues throughout life, but as babies our sense of touch plants the seed for the quality and tenor of our social interactions later on.

A particular type of nerve, found only under hairy skin (on the arm or face, for example), is responsible for the rewarding emotional import of touch. They’re called C-tactile (CT) afferents, and scientists believe they’re crucial to the development of the human brain, too.

They might even play a role in autism, writes Francis McGlone in a comprehensive report published yesterday in Neuron. He and his colleagues in Liverpool and Sweden suspect that since CT afferents trigger the same brain areas that are implicated in autism studies, then autism might be detectable early on. It makes sense—many autistic people have trouble processing visual, tactic, or  information because they’re prone to sensory overload. The otherwise simple act of looking someone in the eye or engaging in conversation is instead imbued with a very intense range of sensations.



Two Swedish scientists, Karl-Erik Hagbarth and Ake Vallbo, were the first to detect CT fibers in humans (they were previously discovered in cats, monkeys, and rats), using a technique called microneurography, in which a tungsten microelectrode penetrates the skin and records complex electrical signals underneath the surface.

Here’s Virginia Hughes, writing for Only Human:

                       

Deciphering the code of these nerves is difficult and takes a lot of patience. “It’s like putting a microphone into a United Nations convention — there’s lots of different languages you’re going to be hearing,” McGlone says. “I think five people on this planet can record from C-tactile afferents.” These trained scientists can hear the language (that is, a certain pattern of electrical waveforms) of the CT afferents only when the skin is gently stroked.

In 2009, McGlone’s team found that when they stroked subjects’ arms at different speeds, specific velocities of stroking generated the most pleasant sensations—and those velocities correlated with the velocities that activated CT nerves. Three years later, they saw that stroking CT fibers triggered brain activity in the posterior insular cortex and the mid-anterior orbitofrontal cortex, both involved in emotion processing. These are the same brain areas detailed in studies on autism. Hairless parts of the palm, by contrast, stimulated non-emotional parts of the brain.

A separate team at Yale University is looking into the effect of stroking on the brains of children with autism. Other senses—taste, hearing, and seeing—are grounds for investigation, too.

Perhaps most intriguing about the touch aspect, though, is the idea that it could influence autistic people’s sense of self. Here’s Hughes again:

   

Stroking CT fibers also activated a brain region called the angular gyrus, which is involved in our internal representation of our body. (In studies of epileptic patients, stimulating this region leads to dramatic out-of-body experiences.) This result is intriguing, McGlone says, because it suggests that CT afferents are involved not only in our awareness of others, but in our physical sense of self.

Using touch as a gateway could help us understand how autistic people experience the world, and possibly the origins of their unique way of perceiving it.

Article link:http://www.pbs.org/wgbh/nova/next/body/clue-to-autisms-roots-could-lie-beneath-the-skin/] [url]http://www.pbs.org/wgbh/nova/next/body/clue-to-autisms-roots-could-lie-beneath-the-skin/[/url]