Dopamine, one of the common neurotransmitters, underlies our ability to move, to learn, and to feel reward and euphoria. It accomplishes all of these roles by acting in four main pathways through the brain. For example, if dopamine transmission goes awry in the nigrostriatal pathway, Parkinson’s symptoms can occur. Alternately, dysregulation in the mesolimbic pathway can lead to gambling or drug addiction. This is because the mesolimbic pathway is involved in feelings of reward and pleasure.
Though neuroscientists are not sure what exact role dopamine plays in the reward system, we at least know that dopamine has an important role in regulating our sensations of euphoria. During enjoyable activities such as eating chocolate and having sex, an area of the brain called the ventral tegmental area releases dopamine into the reward pathway, which runs through parts of the brain responsible for emotion, such as the limbic system.
But while our desire for saturated fats and sex has obvious evolutionary benefits, cognitive musicologists do not understand why we experience intense pleasure when listening to music we enjoy. Linguist Steven Pinker has even referred to music as “auditory cheesecake” (Pinker, 1997). Though Pinker’s claim has been thoroughly criticised as being anti-music, recent research demonstrates how music does cause the same patterns of brain activation as that infamous cheesecake.
PET, a neuroimaging technique that shows brain activity, has been used to demonstrate that the mesolimbic pathway is active when we listen to music that gives us pleasure, though not when we listen to emotionally neutral music. Anne Blood and Robert Zatorre at McGill University enlisted the help of music students who commonly experience a “chill” or a “shiver down the spine” when they listen to certain pieces of music they enjoy. When the students experienced a chill in the PET scanner, Blood and Zatorre could see activity in the left nucleus accumbens and other areas that form part of the dopamine mesolimbic pathway.
However, seeing activation in a part of the brain associated with dopamine does not prove that dopamine is actually being released into one of its pathways. So Zatorre teamed up with “chill” expert Valorie Salimpoor to test if dopamine is released when participants experienced a chill. Participants listened to music that they enjoyed and were injected with a radioactive drug that binds to the same receptors as dopamine, called[11C]raclopride. The PET scanner measured the amount of [11C]raclopride that did not bind to receptors. This meant that if the brain released dopamine, the [11C]raclopride would not have as many receptors to bind to because the dopamine would be attached to those receptors already.
Zatorre and his colleagues found that dopamine was indeed released when the participants experienced a chill, primarily in the nucleus accumbens and other regions of the mesolimbic pathway. But they did not stop there. They also took fMRI scans of their participants, which allowed them to look at what parts of the brain were active on a more detailed timescale.
They found activity in the caudate, an area involved in regulating reinforcement of pleasurable stimuli, when the participants were anticipating the chill. At the actual time of the chill, however, activity moved to the nucleus accumbens. The team of neuroscientists believe their results show that dopamine is released in more than one area during a chill, and that leads to widespread effects throughout the brain, which explain why music has universal effects (Salimpoor et al., 2011).
However, it might not be that simple. Music preferences may be partially due to another function of dopamine: coordinating our ability to move. The nucleus accumbens, which is generally active when we enjoy something, also has links to other areas of the brain that neuroscientists know are involved in movement. One of the other four dopamine pathways is the nigrostriatal pathway, and it controls our ability to move. The nucleus accumbens projects to the substantia nigra, the “nigro” part of the nigrostriatal pathway. The interaction between the mesolimbic (reward) and the nigrostriatal (movement) pathways might be what makes us want to dance to music that we like (Koelsch, 2010).
This interaction has particularly important implications for Parkinson’s Disease patients. Parkinson’s occurs when the cells in the substantia nigra degrade. The lack of transmission in the nigrostriatal dopamine pathway leads to movement symptoms such as tremors and rigidity. Music therapists believe that music can ease the symptoms of Parkinson’s. One study found that motor responses and even emotional function improved when Parkinson’s patients participated in music therapy, by listening to relaxing music, playing instruments, and moving freely to music (Pacchetti et al., 2000). The rhythm of music seems to give Parkinson’s patients the ability to move and to control their movements. The researchers theorised that dopamine was released in both the nigrostriatal and the mesolimbic pathways, which allowed the patients both to move and to enjoy moving.
The effect that music has on dopamine release and transmission is still being studied by many neuroscientists, but it is becoming clear that music has an effect on the ancient and powerful reward circuits, as well as the pathways that allow us to move. Cognitive musicologist Henkjan Honing believes that comparing music to auditory cheesecake might not be as callous as it originally seemed (Honing, 2011). Music gives us chills and makes us dance; even with no convincing evolutionary explanation, we cannot ignore music’s power.