Anyone who’s ever watched a horror film will know that the sound of two clashing notes evokes a visceral response in most people. Among Western listeners there’s a strong preference for consonance, which exists even from infancy; consonance is the pleasing mixture of two tones, while dissonance is their clashing. (For a good example of both, see this video.) It’s controversial whether the same preferences exist in other cultures, but new research indicates the preferences might be wired in our brains.
The prevailing theory of music in the brain is that dissonant combinations share frequencies that are a bit too close. When these frequencies are perceived by the cochlea, the part of the inner ear that translates sounds to nerve impulses, they can’t be well distinguished. Because similar frequencies are processed next to one another on the cochlea, their nerve signals can interfere with one another. The perception is a grating effect, called “beating.” Read More
Listen to this: Scientists, experimenting with guinea pigs, have used the electrical potential of the inner ear to power a 1-nanowatt wireless radio transmitter.
The cochlea, or inner ear, converts the mechanical energy of sound into electrical signals to the brain. The electrical potential in the ear comes from the difference in concentration of potassium ions in fluid separated by membranes in the inner ear, creating the equivalent of positive and negative poles of a battery. To this cochlear battery, researchers hooked up a wireless radio transmitter, with a power of one nanowatt, one billionth of a watt (for reference, a typical lightbulb is 60 watts), which radioed a measurement of the ear’s electrical potential to the researchers, according to their report in Nature Biotechnology.
Whatcha looking at? This is just my face.
This new leaf-nosed bat species was recently discovered in Vietnam. What’s with the strange nose? Scientists think that its protuberances and indentations help the bat in echolocation. Come to think of it, it does kind of resemble another excellent sound detector: the inside a cat’s ear.
As strange as the Hipposideros griffini’s nose is, it’s really got nothing on the star-nosed mole.
[via National Geographic News]
Image courtesy of Vu Dinh Thong / Journal of Mammalogy
Spiders are covered with fine hairs that can detect the faint movements of an enemy creeping closer, or a prey insect moving nearby. Scientists had long thought that these hairs functioned like the hairs humans have in our ears, which each tremble in response to a specific frequency and have to work together for us to hear sounds. But a new experiment suggests that each individual hair on a spider is capable of responding to a whole spectrum of sound, thus acting as an ear all on its own. As Dave Mosher writes at Wired:
The hairs responded best to sounds between about 40 Hz, a low rumble of bass, and 600 Hz, a car horn (humans ears can detect between 20 Hz and 20,000 Hz). That they picked up such a wide range of frequencies at all could overturn previous assumptions about how trichobothria [as the hairs are called] work.
“They operate like band-pass filters or microphones, not like the hairs in a human ear,” Bathellier said. In effect, each hair is its own ear that filters out background noise and zeroes in on biologically relevant information, such as an unwary cricket’s hopping or a spider’s sneaking.
How all these tiny “ears” work together, though, is still a mystery—further studies will have to investigate how the hairs’ vibrations affect spiders’ nervous systems.
What’s the News: A new type of ear bud hacks the ear’s reflexes, reducing its natural damping so you don’t have turn the volume up so high to get your jam on. It also cuts down on all that unsightly “leathering” on your eardrum…
Those delicious chills you get as your favorite piece of music reaches its climax? They’re the result of a glorious spike of dopamine in your brain–that’s the same neurotransmitter that’s involved in reward, motivation, and addiction.
In a nifty series of experiments published in Nature Neuroscience, researchers determined that music provokes floods of dopamine in music lovers. Study coauthor Valorie Salimpoor notes that dopamine has long been known to play a role in more physical activities like taking drugs and having sex, but this research highlights its role in other aspects of our lives.
“It is amazing that we can release dopamine in anticipation of something abstract, complex and not concrete,” Salimpoor said. “This is the first study to show that dopamine can be released in response to an aesthetic stimulus.” [Discovery News]
A brain is a terrible thing to waste–and your brain knows that. A new study of congenitally deaf cats has shown that some parts of their brains which would typically work on hearing are repurposed, and instead help out with vision. As a result of that clever efficiency, these deaf cats have superior peripheral vision and motion-detection abilities than cats with normal hearing.
Researchers say the human brain may perform the same trick.
For years, researchers have known that deaf people often have superior peripheral vision and motion detection, but just how the brain creates these advantages was unclear. “Over the years, we’ve speculated about how these changes might be taking place,” says neuroscientist Helen Neville of the University of Oregon in Eugene, but a clear cause has been elusive. [Science News]
The invention of the microscope allowed scientists to peer into the tiniest of cells. Now, imagine a device that can not just look into minute cells, but can also listen in on their activities.
A team of scientists is building a “micro-ear” that uses tiny beads and lasers to amplify and measure vibrations on a molecular scale. The team hopes the new device will become standard lab equipment soon, allowing scientists to listen to the movement of bacteria such as E. coli as well as microorganisms that cause diseases like sleeping sickness [The Daily Beast].
Bats and dolphins are two of the most celebrated users of echolocation, employing high-frequency sounds to locate prey, find their way, or to communicate. Now a new set of findings in Current Biology show that not only do the two different kinds of mammals use the same method, they also evolved nearly the exact same molecular means for hearing at high frequencies.
That second part was a surprise, study author Stephen Rossiter says: “It’s common on a morphological scale but it’s assumed not to occur at a DNA level because there are so many different ways to arrive at the same solution” [BBC News]. That is, while it’s quite common for different species to separately evolve similar features—like the tusks of elephants and walruses—it’s quite unlikely that natural selection working in separate species would settle an essentially identical gene and protein for growing tusks, hearing high-frequency sounds, or anything else. Or so the thinking went.
Tinnitus, the perceived ringing and buzzing in one’s ears, may not be fully understood, but what is known is that it can severely disrupt a person’s life. Treatment for the condition has been unreliable, but now scientists are reporting a new way to turn down the ringing by turning up music, according to a new study.
Scientists altered participants’ favourite music to remove notes which matched the frequency of the ringing in their ears. After a year of listening to the modified music, individuals reported a drop in the loudness of their tinnitus [BBC News]. Participants who listened to music in which notes of a different frequency were removed reported no such improvement. The treatment could be a cheap way to help the three percent of the population that suffers from tinnitus, say the researchers, who published their findings in the Proceedings of the National Academy of Sciences.