As early as the 1960s, dentists found that dental surgeries with music playing were less painful for their patients. Now a possible explanation for this observation seems to have been found in animal experiments: When pain-plagued mice hear sounds, nerve pathways in their brains that are responsible for pain perception are inhibited. However, the analgesic effect exists only with soft tones and noises. A team of researchers 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 disturbing noises to experimental mice with inflamed paws. Meanwhile, they touched the sensitive parts of the body more and more until the animals felt pain and withdrew their paws. The scientists found that the animals withstood stronger touches when they had heard music or sounds for about 20 minutes. However, these were only allowed to be slightly louder than the ambient noise. On the other hand, what the mice heard did not affect their perception of pain. The simultaneous measurement of brain activity showed that the quiet noises inhibited nerve pathways that connect the auditory cortex to the thalamus. The brain region is involved in pain processing. As a result, the pain threshold of the animals increased.
The researchers checked in additional measurements that the noise was actually responsible for pain relief: behavioral tests and the determination of the "stress hormone" cortisone in the blood of the animals confirmed that the hearing had no influence on the fear and stress level of the mice. Even by distraction, the results could not be explained alone: the researchers repeated their attempts on three different days. Then they tested the pain sensation of the mice on two days without the influence of noises and found that the animals continued to suffer from less pain.
The results cannot be easily transferred to humans: In the human brain, there are even more brain regions relevant for pain perception that also react to music. However, the study provides the first neurobiological basis on which future studies with humans can build on. It would be conceivable that the quiet, pain-relieving noises could be used both in music therapy and as a supplementary offer in pain therapy.
