It may come as a surprise, but music is a tried-and-true therapy for healing in the eyes of science. Numerous studies support its benefits in combination with other treatments, as well as on its own. Still, we don’t know much about its mechanism—we know that sound can provide physiological benefits, but not how.
A new study in mice, published Thursday in the journal Science, reveals a recipe for leveraging music as a potential pain reliever and providing a low-cost, widely accessible alternative to traditional pharmaceuticals.
A team of neuroscientists from China and the U.S. injected the hind paws of lab mice with complete Freund's adjuvant, a solution that causes inflammation and pain. Then they prodded the hind paws and observed the threshold at which the mice flinched—providing a measurement of each animal’s tolerance for pain.
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The team went on to play sounds at levels slightly higher than background noise and observed what kinds of effects these sounds had on the mice’s pain tolerance. It seems like the mice weren’t music snobs: They reacted equally to classical music, dissonant music, and white noise when each was played 5 decibels louder than ambient noise.
Whatever the music was, the overall effect was remarkable: The sounds being played led to significantly lower pain levels for the mice, a result that persisted even two days later.
“In the future, these findings could spur the development of alternative interventions for treating pain,” the authors wrote in the new paper.
Once they had evidence that the music therapy worked, the researchers peered into the mice’s brains and recorded the regions that lit up when they played the soothing sounds. They traced the effects through regions called the neocortex, thalamus, and brainstem to show how the music competed for airtime in the brain with pain signals from the paw.
According to an accompanying perspective article in Science written by Heidelberg University biologists Rohini Kuner and Thomas Kuner, previous explanations for the pain-relieving properties of music focused on sounds’ ability to distract listeners. While sound “likely contributes to distraction,” they wrote that the study details a new and distinct pathway for pain suppression.
They also speculated that the secret sauce that explains the 5-decibel effect was its ability to trigger defensive instincts in the mice. If so, a fight-or-flight response would have lowered their perceptions of pain as the mice focused on more pressing concerns, like avoiding a potential threat. “From an evolutionary perspective, it makes sense that sound-driven defense behaviors are acutely accompanied by pain suppression,” the Kuners wrote.
Even so, we need to study this phenomenon in more depth before we can start firing off pain-relieving noises to patients in need.
“Using rodents to study how music and sound are related to pain presents major challenges, not least because it is unknown how animals perceive music,” the Kuners wrote.
On this point, the Chinese and American team seems to agree. “The neural mechanisms underlying music-induced analgesia in humans are doubtlessly more complicated than those revealed in mice,” they wrote.
