Specific musical anhedonia, an inability to experience pleasure from music, affects 3-5% of the population. Researchers at the University of Barcelona and the Montreal
Neurological Institute and Hospital of McGill University have discovered
that people with this condition showed reduced functional connectivity
between cortical regions responsible for processing sound and
subcortical regions related to reward.
To understand the origins of specific musical anhedonia, 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 an fMRI machine while providing
pleasure ratings in real-time. To control for their brain response to
other reward types, participants also played a monetary gambling task in
which they could win or lose real money.
‘Musical anhedonics exhibit reduced functional connectivity between cortical regions associated with auditory processing and the Nucleus Accumbens.’
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.
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 fact that subjects could be insensible to music while still
responsive to another stimulus like money suggests different pathways to
reward for different stimuli. This finding may pave the way for the
detailed study of the neural substrates underlying other domain-specific
anhedonias and, from an evolutionary perspective, help us to understand
how music acquired reward value.
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.
This latest research reinforces the importance of neural connectivity
in the reward response of human beings.
"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," says Robert
Zatorre, an MNI neuroscientist and one of the paper's co-authors.