Sound Seen in a New Way

Typically, sound is not considered as more than just the music pulsing through earbuds, sirens and car horns, a neighbors house party, crickets on a summer night. Music has commonly been used for expression, enjoyment, education. It has been found to affect stress, which may be one reason people keep music at close hand throughout their lives. Sound is everywhere, even at times when we think there’s nothing to be heard…

One such sound is ultrasound, which is so high-pitched as to be inaudible to the human ear. Yet it has been harnessed for use in non-invasive medical examinations for quite some time now, sonograms being one common example.

A recent scientific study, published September 15, 2015, successfully discovered a new capability for sound: controlling neurons. The process has been called sonogenetics, the use of ultrasound to activate or silence specific neurons in the brain. Harassing the ability to target individual cells could revolutionize medical practices concerning cell malignancy or deterioration.

“A major challenge in neuroscience is to reliably activate individual neurons, particularly those in deeper brain regions. Current optogenetic approaches require invasive surgical procedures to deliver light of specific wavelengths to target cells to activate or silence them. Here, we demonstrate the use of low-pressure ultrasound as a non-invasive trigger to activate specific ultrasonically sensitized neurons in the nematode, Caenorhabditis elegans [worm].”

Light used during optogenetics scatters in tissue and does not easily reach the interior of a body. Sound waves, on the other hand, travel right through to the cells a doctor or scientist targets. It has in the past been tested in studies concerned with brain cancer and Alzheimer’s disease.

During the conducted experiment, ultrasound was directed at a worm that had been coated in gas-filled bubbles that conducted the ultrasound waves through affected pores called TRP-4. The worms inner neurons, specifically those that controlled movement, could thus be directly affected by ultrasound waves. In response to the sound waves, the worm entirely reversed its forward movement. Humans can similarly have gas bubbles injected into their bloodstreams to facilitate the passage of ultrasound waves, improving the outlook for further advances in sonogenetics.

C. elegens, the test subject. https://cbs.umn.edu/cgc/what-c-elegans
C. elegens, the test subject.

One thing to consider, however, is that worms have an extremely simple nervous system. Michael Hausser, professor of neuroscience at University College London, explained in an interview with the BBC that

“…the worm is only 1mm long…with the neurons only 25 micrometres beneath the surface: a quarter of the diameter of a human hair. This makes it an ideal organism for ultrasound to influence neural activity…It will be a much greater challenge to get such a technique to work in a big brain within a skull.”

Advances in scientific usage of sound presents a new way to appreciate just how significant a role sound plays in our world, heard and unheard. Just as music industries use sound to satisfy listeners, the medical and scientific industries are using sound to advance their healing abilities. Maybe one day ultrasound treatments will be as common as turning on the radio.

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