How does the brain process surprise in pleasant music?
People who find a piece of music highly enjoyable show increased activity and stronger connectivity in their brain's reward centers during unexpected musical moments.
Source
Surprise-related activation in the nucleus accumbens interacts with music-induced pleasantness
What they did
Researchers scanned healthy participants using fMRI while they listened to three naturalistic piano pieces of varying complexity. A separate group of musically trained judges annotated the locations and intensity of surprises throughout each composition. Outside the scanner, participants listened to the pieces again to continuously rate their subjective emotional arousal and pleasantness. The researchers then analyzed whether activity in the nucleus accumbens, a key reward region, differed between individuals who experienced high versus low overall pleasantness during the music.
What they found
The researchers found that musical surprises triggered brief increases in emotional arousal and prompted shifts in subjective pleasantness. At the neural level, highly surprising moments activated the auditory cortex, anterior insula, and ventral striatum across all participants. Crucially, only the participants who reported high pleasantness during a piece showed elevated nucleus accumbens activation in response to highly surprising musical events. Furthermore, in the most pleasant piece, this high-pleasantness group exhibited stronger functional connectivity between the nucleus accumbens and the auditory cortex during surprising moments compared to the low-pleasantness group.
The limits
What it doesn't show
To begin with, because the study relied on only three musical pieces from Western classical and art traditions, the findings may not generalize to other musical genres or cultural styles. Additionally, because the emotional ratings were collected during a repeated listening session, the musical events were no longer completely novel to the participants when they reported their pleasantness. Furthermore, the researchers did not measure the participants' subjective experience of surprise directly, relying instead on annotations from an independent group of musicians. Finally, because participants were not randomly assigned to the high- and low-pleasantness groups, other underlying individual differences could account for the observed neural variations.
Key terms
- Nucleus accumbens
- A key subcortical brain structure within the mesolimbic reward pathway that integrates emotional, cognitive, and motivational information.
- Superior temporal gyrus
- A cortical region housing primary and higher-level auditory processing areas, critical for tracking acoustic features and generating musical expectations.
- Predictive coding
- A theory proposing that the brain continuously generates and updates internal models of the environment to anticipate incoming sensory inputs.
- Prediction error
- The discrepancy between what an organism expects to experience and what it actually experiences, which serves as a signal to update future predictions.
- Functional connectivity
- The temporal correlation of neural activity between spatially distinct brain regions, suggesting they are working together to process information.
- Valence
- The subjective positive or negative quality of an emotional experience, often represented in this study as music-induced pleasantness.
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Quiz yourself
From a predictive-coding viewpoint, what purpose do musical surprises serve for an organism?
Common questions
Why did the researchers collect brain scans and emotional ratings in separate sessions?
They separated the fMRI scan from the rating task to prevent the cognitive effort of continuously reporting emotions from altering the natural brain activity associated with simply listening to and enjoying music.
How did the researchers determine which moments in the music were 'surprising'?
They had an independent group of musically trained judges listen to the pieces and mark the exact times they felt a musical surprise occurred, using a crowd-sourcing approach to rank the intensity of each surprise.
Did the participants' musical training or age affect the results?
No, the researchers confirmed that the high-pleasantness and low-pleasantness subgroups did not differ significantly in terms of age, gender, or prior musical experience.
What is the significance of the connection between the nucleus accumbens and the auditory cortex?
This connection represents the interaction between sensory processing (tracking musical patterns in the auditory cortex) and emotional reward (the nucleus accumbens), suggesting that enjoying musical surprises relies on these regions communicating effectively.
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