Experiments on mice show that sound increases pain tolerance
Photo: iStock Imagine you are having a root canal at a dentist. But instead of local anaesthetic, you are listening to Eine kleine Nachtmusik. A new study that carried out experiments on mice, has shown that such a scenario could be possible someday.
A team of neurobiologists at the National Institute of Dental and Craniofacial Research in the United States, used mice to gain a deeper understanding of why music eases pain.
Scientists and medical professionals have been studying the numbing effects of sound since the 1960s using a variety of musical artists, including Michael Bolton and Wolfgang Amadeus Mozart.
The neurobiologists conducting the current study gave painful injections to mice on their paws. The rodents were then tested by having thin filaments inserted into their paws at various pressures to see how they would react.
The researchers viewed the mice’s licking, flinching, or pulling back of their paws as signs that they were in discomfort.
They played Johann Sebastian Bach’s Réjouissance to the rats at 50 or 60 decibels (dB) for 20 minutes each day in a room with a background noise level of 45 decibels.
A sound level of 50 dB or lower seemed to numb the animals. The mice didn’t flinch when the researchers prodded their swollen paws.
The animals were substantially more responsive to the stimulus when the noise was louder. It only needed a third of the pressure to elicit a response from the subjects, in comparison to when there was no music.
The researchers repeated the procedures. But this time they monitored a red fluorescent dye injected into the mice’s auditory cortex, the area of the brain responsible for processing sounds.
They discovered a lot of fluorescence in some dense areas of the thalamus, the centre of sensory processing. This indicated that there may be linkages between this area and the auditory cortex that contribute to the suppression of pain.
Further research by inserting tiny electrodes into the brains of the animals showed that the auditory cortex’s activity dropped in response to relatively mild noises.
The mice appeared to experience less pain when the team artificially disrupted the communication between the auditory cortex and the thalamus by directing light pulses to these particular neurons.
The scientists found that low sounds appeared to dampen pain processing in the thalamus by blunting neurological impulses between the auditory cortex and thalamus.
Even after the mice stopped hearing the music, the analgesic effects persisted for up to two days.
The researchers’ next goal is to experiment with humans. They can’t use intrusive techniques to examine the connections between the auditory cortex and thalamus in the human brain.
But they can play low-frequency sounds for volunteers and use magnetic resource imaging images to track their thalamus activity. The discoveries may provide scientists with new approaches to treating human pain, other scientists feel.
The study titled Sound induces analgesia through corticothalamic circuits was published July 7, 2022, in the journal Science.
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