Ya sea que la estemos escuchando a través los pequeños audífonos del iPhone en nuestro recorrido diario al trabajo o llorando en un concierto de John Mayer, hay un lugar especial en nuestros corazones para la música. Pero, ¿cuál es la base biológica de esa sensación mágica que sentimos al escuchar nuestra canción favorita?
Muchos científicos han teorizado que la naturaleza universal de la música debe tener un origen evolutivo. Charles Darwin, el naturalista mejor conocido por sus contribuciones a la ciencia de la evolución, sugirió que los humanos usan la música para atraer parejas, lo cual explicó minuciosamente en su libro El origen del hombre, y la selección en relación al sexo. Darwin creía que nos «esforzábamos por hechizarnos unos a otros con notas musicales y ritmos». Esta idea es comparable a los procesos de la selección sexual guiados por el canto de los pájaros, una teoría de selección de pareja bien conocida. Otros científicos han sugerido que «sentir el ritmo» es una forma de sincronizar los pasos para evitar ser escuchado por los depredadores.
We may never know the exact evolutionary reason for our love of music, but researchers continue to investigate the neurochemical mechanisms that underlie the enjoyment of music. Much research has focused on the role of music on the brain’s reward system. The reward pathway begins in the center of the brain in a region called the ventral tegmental area. Here, special neurons release the neurotransmisor dopamina., which gives you a jolt of pleasure and makes you feel good. In order to make sure you repeat this behavior in the future, the reward pathway is connected to areas of the brain that control memory and behavior, including the nucleus accumbens y prefrontal cortex. Not surprisingly, more dopamine is released when a person is listening to pleasant music.
But dopamina. is not the only neurotransmisor involved in the enjoyment of music. Other studies have found that serotonin is also important. Drugs that act on serotonin are commonly used to treat depresió. In fact, this neurotransmisor is associated with wakefulness and is important for the gut-brain interaction, so it is no surprise that serotonin levels in the nucleus accumbens rise when we are listening to music.
Of course, the reward and pleasure pathways are not the only neural networks activated when we listen to music. So what else might be going on? To answer this question, we must consider the fact that reward is experienced in two chemically distinct phases. The first ‘anticipatory phase,’ which is equivalent to ‘wanting,’ is driven by the dopaminergic neuronal pathways described above. The second ‘consummatory phase,’ which is the ‘liking’ part, is driven by a combination of dopaminergic pathways y opioid receptor activation. Opioids are substances that are medically used to relieve pain. These two phases activate different parts of the nucleus accumbens. Specifically, anticipatory pleasure is linked to a widely distributed network throughout the nucleus accumbens, while consummatory pleasure is linked to a more local aspect of this brain region (Footnote 1).
«…la tristeza provocada al escuchar música puede ser una característica del propio placer…»
Despite this anatomical difference, the dopaminergic y opioid systems are directly linked during feelings of pleasure and reward. Therefore, it seems likely that opioids — in addition to dopamina. — could be involved in the emotions we feel whilst listening to music. Earlier this year, a team of neuroscientists from McGill University conducted a study that explored how the brain’s endogenous (or self-made) opioids may be involved in controlling emotional responses to music.
In order to investigate the role of the opioid system in human subjects listening to music, the research team studied what happens when the opioid system is blocked using a drug called Naltrexone, or NTX. When NTX binds to opioid receptors, it acts as an antagonist, temporarily stopping the action of endogenous opioids that would act on this reward pathway. Previous studies have shown that administration of NTX reduces the rewarding feeling after physical activity, decreases the pleasant feeling after eating, and causes people to generally feel dampened highs and lows and reduced levels of joy and sadness. Based on this previous research, the team hypothesized that giving patients NTX would have the same general dampening effect on both the positive y negative emotional reactions to music, which can also be called musical anhedonia.
For their study, the research team ran a double-blind placebo controlled experiment, meaning that neither the team nor the participants knew if they were getting NTX or a sugar pill. Participants were asked to bring in two of their favorite music recordings that reliably produced intense feelings of pleasure for them. During the experiment, participants either listened to their self-selected music or ‘neutral’ music selected by the researchers. While they listened to the music, both objective and subjective measures were used to quantify their emotional response. These included measuring respiratory rates as well as using electromyography to measure the activity of muscles involved in smiling and frowning.
So what were the results? As expected, NTX reduced the extent of pleasure felt by participants when listening to music. Interestingly, NTX caused a great reduction in those feelings when participants were listening to their favorite songs compared to when they were listening to the control ‘neutral’ music. Importantly, not only did NTX reduce pleasurable feelings, it also reduced negative feelings too! Examination of the electromyograms revealed muscles involved in frowning were activated to a lesser extent in the presence of NTX. By dampening both the positive and negative feelings towards music, NTX had an overall ‘anhedonic’ effect on music.
The results of this study suggest that opioids are involved in regulating both positive and negative emotions that we experience when listening to music.
Although this may seem counter-intuitive since we are talking about pleasure from music, this idea also ties in with other research about the complex interactions that produce musical pleasure. In fact, previous research from the musical anhedonia research group suggests that the sadness elicited when listening to music can be a feature of the pleasure itself, perhaps by a provoking a shared feeling of sadness with other people and the composer of the music. This is why sadness whilst listening to music does not elicit a depressive neurochemical response, but is instead involved in an overall pleasurable experience and relates to the ‘chill’ sensation you get from certain songs.
Alas, the science of music is as complicated as a Bach fugue. Music elicits positive and negative emotions at the same time, while also producing a pleasurable sensation. In fact, this new field of research inspires other questions about the complex interactions of our emotions. Could we use what we’ve learned from music to explain other complex feelings, for example, nostalgia? Alongside these more abstract questions, the McGill University experiment shows that music may be governed by the same hedonic reward system as food, sex, and drugs, which have already been shown to elicit similar ‘anhedonic’ effects in the presence of NTX.
The fact that listening to music triggers such a well-defined neurochemical response may suggest an evolutionary origin for music, but it is hard to draw conclusions at this stage. This study has shown that the strong emotional response to music comprises positive and negative feelings – an advanced system that is likely to have evolutionary significance comparable to some of our most basic human needs like food and sex. It could be that the music reward pathway is hijacking an evolutionary system that was originally involved in something else related to these basic needs, such as responding to animal or human vocalizations.
Although ‘musical anhedonia’ doesn’t fully explain why we like music in the first place, it does explain how music sends shivers down the spine!
Footnote 1: Specifically, consummatory pleasure is linked to the rostro-dorsal quarter of the medial accumbens shell.
Artwork by Jooyeun Lee.
Mallik, A., Chanda, M. L., & Levitin, D. J. (2017). Anhedonia to music and mu-opioids: Evidence from the administration of naltrexone. Scientific Reports, 7, 41952.