Fingerprints Are Tuned to Amplify Vibrations and Send Info to the Brain

By Nina Bai | January 30, 2009 5:50 pm

fingerprintFingerprints are for more than a good grip; they also allow fingers to feel fine textures, according to a new study. As fingers move across a surface, the intricate geography of the finger tips, known as epidermal ridges, help select and amplify just the right vibrations to convey information from the skin to the brain. Neuroscientist Ellen Lumkin compares the ridges on fingers to the cochlea in the ear. “Like the cochlea is a frequency analyzer for sounds, the fingertips are frequency analyzers for fingers,” says Lumpkin [Science News] Fingerprints help filter out the tactile equivalent of white noise.

When a finger sweeps over a finely textured surface, such as a cotton sleeve or a wooden coffee table, the interaction sends a large range of vibrations into the skin. Specialized sensors called Pacinian fibers, the tips of nerve fibers, detect only a select few of the vibrations — those right around 250 hertz — before sending the signal to the brain, where the touch sensation is processed [Science News]. But since Pacinian fibers are located relatively deep—about 2 millimeters—under the skin, researchers guessed that fingerprints help magnify the vibrations.

To study the effect of fingerprints, they created a tactile sensor that closely mimics the actions of our fingers. Their sensor can be equipped with either a smooth fingertip or a “fingerprinted” one. The researchers compared how these two types of fingertips performed on different textures by measuring their pressure variations with a microforce device [Ars Technica]. The “fingerprinted” sensor, which has parallel ridges about half a millimeter apart, imitates the human finger. Like sunglasses that filter out UV light and let the useful visible light through, the artificial fingerprints filtered out vibrations above and below 250 hertz, leaving only the vibrations that could be detected by Pacinian fibers [Science News]. The smooth sensor created less friction and picked up a wider range of unamplified signals, researchers reported in Science [subscription required]. Lead researcher Georges Debrégeas  says, “Fingerprints might actually improve the sensitivity of perception by enhancing the skin vibrations at a frequency that matches the best frequency of these Pacinian corpuscles,” [Nature News].

The researchers noted that their artificial fingerprints worked only if the direction of motion was perpendicular to the direction of the ridges. Thankfully, the whorls, arches, and loops on real human fingertips mean that swiping in any direction will activate the filtering effect. This could imply that the contours of our fingerprints are patterned to optimize texture perception [Ars Technica]. Understanding the physics behind touch could help scientists build better prosthetics for amputees or robots capable of a sensitive touch and delicate handiwork. But the first challenge, the researchers say, is to replicate the results from the elastic faux fingers using real human fingers.

Related Content:
DISCOVER: 20 Things You Didn’t Know About… Skin
DISCOVER: Emerging Technology: Fingerprinting Cybercriminals

Image: Science/AAAS

  • http://Yahoo.com Seth

    Truly amazing. I can just see the headlines on ICR now: Magical fingerprint IMPOSSIBLE for silly evolutionists! Wow. What’s really sad is that they don’t even do actual research. They only scan for articles that are written by those who do the research, and then utilize the G-D of the gaps. Wow though, that is impressive. Fingerprints are effing choice.

  • twilightened

    Actually i was expecting something like that. As far as we know, three senses of humans are working on a “vibration” pattern. Seeing, hearing and the sense of smell. I am not sure about the taste. Now sense of touch is also added. I believe it will follow as well. Pretty interesting though, when i first watched the TED talk about the sense of smell, and the new discovery of the technology of synthetic smell creation, the guy said that we used to think that chemical particles somehow fit in the appropriate blanks in the sensory nerves in the nose. But he said that the nerves actually sense the vibrations of the chemical elements, as they all vibrate in a different pattern. Here is the link for that video:

    http://www.youtube.com/watch?v=yzOcvINn8Iw

  • http://apps.jooopa.net Werner

    Awesome!!

  • http://handlines.blogspot.com h.l.

    “Thankfully, the whorls, arches, and loops on real human fingertips mean that swiping in any direction will activate the filtering effect. ”

    I wonder about this. Arch ridges can be relatively horizontal, i.e. ridges in one direction only (unlike loops and whorls). Does this mean that those with arch fingerprints are less sensitive to swiping sideways i.e. the same direction as the arch ridges? And those with whorls sensitive to any direction? And those with loops particularly sensitive to a side-ways swipe? That’s quite interesting to speculate about.

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    Truly amazing..

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    I always kindof assumed that, go scientists….

  • http://www.paypal.com/ Machelle Chafe

    I really liked your information but sorry to say but this time you may have been too sick when writing because your writing it feels rushed.

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