11 April 2013
This is your brain on iTunes
by Will Parker
Researchers have been using an MRI scanner to work out what happens in our brain when we decide to purchase a piece of music after we hear it for the first time. The study, conducted at the Montreal Neurological Institute and McGill University, pinpoints the specific brain activity that makes new music rewarding and predicts the decision to purchase music.
The participants in the study listened to 60 previously unheard music excerpts while undergoing fMRI scanning, providing bids of how much they were willing to spend for each item in an auction paradigm. The researchers used an interface and pricing-structure that were similar to iTunes. To replicate a real life scenario as much as possible and to assess reward value objectively, individuals could purchase the music with their own money.
"When people listen to a piece of music they have never heard before, activity in one brain region can reliably and consistently predict whether they will like or buy it, this is the nucleus accumbens which is involved in forming expectations that may be rewarding," explained lead investigator Valorie Salimpoor. "What makes music so emotionally powerful is the creation of expectations. Activity in the nucleus accumbens is an indicator that expectations were met or surpassed, and in our study we found that the more activity we see in this brain area while people are listening to music, the more money they are willing to spend."
The study also revealed that the nucleus accumbens doesn't work alone, but interacts with the auditory cortex, an area of the brain that stores information about the sounds and music we have been exposed to. The more a given piece was rewarding, the greater the cross-talk between these regions. Similar interactions were also seen between the nucleus accumbens and other brain areas, involved in high-level sequencing, complex pattern recognition and areas involved in assigning emotional and reward value to stimuli.
The take-away, says Salimpoor, is that the brain assigns value to music through the interaction of ancient dopaminergic reward circuitry, involved in reinforcing behaviors that are necessary for our survival (such as eating and sex) with some of the most evolved regions of the brain, involved in advanced cognitive processes that are unique to humans.
"This is interesting because music consists of a series of sounds that when considered alone have no inherent value, but when arranged together through patterns over time can act as a reward," said co-researcher Robert Zatorre. "The integrated activity of brain circuits involved in pattern recognition, prediction, and emotion allow us to experience music as an aesthetic or intellectual reward."
The study suggests that the interactions between nucleus accumbens and the auditory cortex indicate that we create expectations of how musical sounds should unfold based on what is learned and stored in our auditory cortex, and our emotions result from the violation or fulfillment of these expectations.
"The brain activity in each participant was the same when they were listening to music that they ended up purchasing, although the pieces they chose to buy were all different," added Salimpoor. "These results help us to see why people like different music - each person has their own uniquely shaped auditory cortex, which is formed based on all the sounds and music heard throughout our lives. Also, the sound templates we store are likely to have previous emotional associations."
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Source: McGill University