Quiet sounds relieve pain in mice


As early as the 1960s, dentists found that dental surgery was less painful for their patients while music was playing. Now a possible explanation for this observation seems to have been found in animal experiments: if mice suffering from pain hear noises, nerve tracts in their brain that are responsible for pain perception are inhibited. However, the pain-relieving effect only exists with soft tones and noises. A research team led by Wenjie Zhou from the Chinese University of Science and Technology in Hefei reports on this in the journal Science.

The researchers played music, noise or background noise to test mice with inflamed paws. Meanwhile, they touched the sensitive body parts more and more until the animals felt pain and drew their paws back. The scientists found that the animals could withstand stronger touches after listening to music or noises for around 20 minutes. However, these should only be slightly louder than the ambient noise. However, what the mice heard did not affect their pain perception. The simultaneous measurement of brain activity showed that the quiet noises inhibited nerve tracts that connect the auditory cortex to the thalamus. The brain region is involved in pain processing. This raised the pain threshold of the animals.

The researchers used additional measurements to verify that the noises were actually responsible for the pain relief: behavioral tests and determination of the “stress hormone” cortisone in the animals’ blood confirmed that what they heard had no effect on the mice’s anxiety and stress levels. The results could not be explained by distraction alone either: the researchers repeated their experiments on three different days. They then tested the mice’s pain sensitivity on two subsequent days without the influence of noise and found that the animals continued to suffer from less pain.



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