People who get no joy from listening to music — a condition called specific musical anhedonia — showed reduced functional connectivity between regions in their brains responsible for processing sound and regions related to rewards.
That’s the finding from a new study from researchers at the University of Barcelona and the Montreal Neurological Institute and Hospital of McGill University.
To understand the origins of specific musical anhedonia, which affects between three and five percent of the population, researchers recruited 45 healthy participants who completed a questionnaire measuring their level of sensitivity to music and divided them into three groups of sensitivity based on their responses.
The test subjects then listened to music excerpts inside a functional magnetic resonance imaging fMRI machine while providing pleasure ratings in real-time.
To control for their brain response to other reward types, participants also played a gambling task in which they could win or lose real money.
Using the fMRI data, the researchers found that while listening to music, specific musical anhedonics presented a reduction in the activity of the nucleus accumbens, a key subcortical structure of the reward network.
The reduction was not related to a general improper functioning of the nucleus accumbens itself, since this region was activated when they won money in the gambling task, the researchers reported.
Specific musical anhedonics, however, did show reduced functional connectivity between cortical regions associated with auditory processing and the nucleus accumbens. In contrast, individuals with high sensitivity to music showed enhanced connectivity, the study discovered.
The fact that people can be insensible to music while still responsive to another stimulus — such as money — suggests different pathways to reward for different stimuli, according to the researchers.
This finding may pave the way for the detailed study of the neural substrates underlying other domain-specific anhedonias, the researchers noted. It might also help us understand, from an evolutionary perspective, how music acquired reward value, the researchers added.
Lack of brain connectivity has been shown to be responsible for other deficits in cognitive ability.
Studies of children with autism spectrum disorder, for example, have shown that their inability to experience the human voice as pleasurable may be explained by a reduced coupling between the bilateral posterior superior temporal sulcus and distributed nodes of the reward system, including the nucleus accumbens, the researchers pointed out.
Their new study reinforces the importance of neural connectivity in the reward response of human beings, they add.
“These findings not only help us to understand individual variability in the way the reward system functions, but also can be applied to the development of therapies for treatment of reward-related disorders, including apathy, depression, and addiction,” said Dr. Robert Zatorre, an MNI neuroscientist and one of the paper’s co-authors.
The study was published in the journal Proceedings of the National Academy of Sciences.
Source: McGill University
Photo: Using the fMRI data, the researchers found that while listening to music, specific musical anhedonics presented a reduction in the activity of the Nucleus Accumbens, a key subcortical structure of the reward network. Credit:Hans Braxmeier.