By Timur Katsnelson, Neurobiology, Physiology, and Behavior, ‘19
Author’s Note: Like everyone else, I love music- especially the works of my favorite artists. There is nothing better than listening or jamming out to your favorite song. The human love for music is a powerful binding force, but why do we even like it? What are the underlying physiological responses of our enjoyment? I wanted to explore the functions of our brain as they relate to enjoying music, and found some interesting results about what scientists have uncovered thus far.
One of the most distinguishing characteristics of the human brain is the ability to interpret and feel emotions regarding complex environmental stimuli such as visual arts and music. Even more interesting is the seemingly infinite amount of variation in how each individual perceives these stimuli, or rather, the reason why one person may love to listen to Vampire Weekend while another casually listens to a lo-fi playlist. There are structural similarities shared by all humans, crafted over millions of years of evolution, but they do not account for different tastes. Neuroscientists who study dopaminergic pathways and other neural structural mechanisms have made several initial steps in understanding what physiological functions music serves to humans. So far, it has been established that musical appreciation and preference are related to the connectivity of white matter between regions in the auditory cortex and the regions processing emotion; variations in activity from neurons related to emotional communication could explain our differences in musical taste. Answering questions about the effects of music on the brain will undoubtedly help to answer larger questions about music’s evolutionary purpose and its profound impact on human cultures.
Neuroscience of Pleasure and Reward
Motivation, emotion, and arousal can all be attributed to elevated activity in the reward centers of the brain. As these traits are known to have implications in addiction, their cellular manifestations have been studied for several decades. The ventral striatum, midbrain, amygdala, and some areas of the prefrontal cortex have all been demonstrated, in varying degrees, to being recruited in instances of drug use. The dopaminergic pathways of the brain refer to a series of densely-packed neuronal connections that are stimulated by the neurotransmitter dopamine to propagate signals. Collectively, these regions of the brain are responsible for our response to natural stimuli and our actions to either seek or avoid them.
The brain’s reward centers are also known to be active in communal interactions, suggesting that there is a benefit to acting in a socially-positive way. Interestingly, the emotions experienced by humans when listening to their favorite music is correlated to the engagement of the same dopaminergic pathways as those that are stimulated during drug use or social interactions. It is important to note that the similarities between which parts of the brain are engaged when listening to music, using drugs, or being with people do not imply that the physiological or psychological effects are closely mimicked in the process. Neurons communicate via action potentials. These synaptic changes in membrane voltage effectively signal messages to neighboring neurons, but nothing about them is inherently meaningful. Since all action potentials are the same, it is the frequency of their appearances that convey messages. As it relates to the similarities in regions activated by both drug use and music, increases in activity do not necessarily equal the same frequencies of action potentials. Nonetheless, positron emission tomography (PET) scans observing pleasurable responses to music in animals and humans show the same regions of the brain being activated. Increases in dopaminergic pathway activity in the nucleus accumbens (NAc), ventral pallidum, ventral tegmental area, amygdala, hippocampus, and other areas of the midbrain collectively correlate to the reward process [3].
The Brain’s Response to Music
There are several experiments that examine the neural response to music, or “aesthetic responses” as some scientific literature has described. PET studies visualized the neural relationship with ‘intensely pleasurable’ responses to music [2]. Intensely pleasurable responses are defined as euphoric sensations in reaction to music, characterized by “shivers-down-the-spine” or “chills” [1]. In addition to observing activity levels within the brain, researchers monitored heart rate and blood flow in the brain. When excited by external stimuli, the central nervous system commands a response throughout the body to heighten the senses and increase awareness. A study by Blood et al. measured heart rate and cerebral blood flow of subjects listening to chill-inducing songs. Increases in the intensity of stimulation from a song were shown to increase blood flow in areas of the brain’s reward centers, as well as the heart rate. It is known that pleasure derived from music activates regions between the brain’s auditory region, specifically the superior temporal gyrus, and the reward centers such as the ventral and dorsal striatum. Parts of the basal ganglia, the ventral and dorsal striatum are largely responsible for motor function as it relates to desire and reward. Despite these findings, the exact connection between physiological sensations and aesthetic responses in the brain are ambiguous [1].
Evolutionary Advantage?
The question of music’s evolutionary purpose has been postulated for over a century, including in Darwin’s The Descent of Man, and Selection in Relation to Sex [3]. To some experts, music is considered to be the result of an evolutionary exaptation. That is, music’s purpose was not selected for its current use by humans. Rather, it came about as a result of excited neural pathways that engage emotional responses [1]. Others suggest that music is an important communicative tool that possibly preceded speech and language [5]. In this case, the chills elicited by music are physiologically measurable emotional responses, which signify that music is effectively a resource for communicating emotions [3].
Based on this idea, some researchers wanted to examine responses to music between individuals and compare them to the structural foundations of their emotional expressiveness capacity. Musical anhedonia is used to describe a condition for those who do not exhibit any pleasure from music, as there is no dopaminergic response from the reward centers. The flat affective response of individuals with this condition could be compared to the brains of subjects with affective responses to music. One such study found that patterns of white matter networks between the superior temporal gyrus through the ventral and dorsal striatum predicted the amount of reward response elicited by music. As the name suggests, the superior temporal gyrus is part of the temporal lobe- which is associated with the auditory cortex. This path of white matter moves from the auditory processing system to the basal ganglia. The aforementioned ventral and dorsal striatum, both parts of the basal ganglia, are involved in motor function. However, there could be other reward-related responses elicited from these structures, such as chills. Some researchers postulate that music may have had its origins from chill-responses to pleasurable sounds in the evolutionary environment, which may have motivated our ancestors to create their own response-evoking sounds [3]. Chills are viewed as a form of communication, demonstrating a positive response to sounds. Therefore, finding this white matter network may suggest that, in addition to emotion, there is a structural aspect of music involved in communication [3].
Music’s Effect on Other Species
A less studied and even less understood aspect of music is its meaning and interpretation by other species. Understanding the effect of music on other animals could provide a glimpse into music’s inherent biological meaning. Although it is clear that the pleasures that humans experience from music are not necessarily akin to the experience of animals, research suggests that music genres can affect the mood or behavior of captive animals. Country music has been shown to improve the mood and well-being of cattle, as opposed to more harsh or erratic-sounding music such as rock and jazz. One study specifically showed that cows more readily entered milking parlours when exposed to country music. However, these foundational animal studies have strictly been observant of the behavior and activity of the cattle [4]. Examining the neurological differences in musical preference or indifference in cattle would provide more concrete evidence of the neurological change that leads to the observed behaviors.
Further Discussions and Research
The research discussed thus far provides clues into the baseline purposes of music and the nature of its evolutionary impact. Yet, there are still many interesting existential discussion topics surrounding the origins of music and its purpose. Grounded biological inquiry, however, will be the most essential tool to get closer to understanding the extraordinary impact of music on human culture, communication, and evolution. Moving forward, researchers should continue to address the differences between individual preference and capacity to respond to music by studying differences in neural matter and structure. Most evidence suggests that music has a strong correlation to emotional expression, so examining the mechanisms of communication and interpreting abstract stimuli as emotional cues will help researchers understand how music can be physiologically deciphered and responded to. On a broader scale, examining global differences in musicality could provide insight into how different cultures and languages relate to their historically popular forms of music and rhythms. Could phonetic or rhythmic patterns in language correspond to preferences for certain tempos, measures, rhythms, or lyrics in music? These questions would be better served in a separate discussion but for now, go back to enjoying your favorite song.
References:
- Blood, A. J., & Zatorre, R. J. (2001). Intensely pleasurable responses to music correlate with activity in brain regions implicated in reward and emotion. Proceedings of the National Academy of Sciences of the United States of America, 98(20), 11818-23.
- Matthew E. Sachs, Robert J. Ellis, Gottfried Schlaug, Psyche Loui (2016). Brain connectivity reflects human aesthetic responses to music, Social Cognitive and Affective Neuroscience, Volume 11, Issue 6, Pages 884–891.
- Psyche Loui et al. (2017). White Matter Correlates of musical Anhedonia: Implications for Evolution of Music. Frontiers in Psychology, Volume 8, Article 1664.
- Deborah L. Wells (2009). Sensory Stimulation as Environmental Enrichment for Captive Animals: A Review. Applied Animal Behaviour Science. Volume 118, Issues 1-2, Pages 1-11.
- Steven Mithen (2007). The Singing Neanderthals: The Origins of Music, Language, Mind, and Body.