Music, dance… How the brain and body move in rhythm
During their voyage to the Kerguelen Islands at the beginning of the last century, Raymond Rallier du Baty and his crew landed on Tristan da Cunha, which was then inhabited by shipwreck survivors whose contact with civilization depended almost entirely on ships straying off course. When one of the adventurers had the idea to play the accordion, he elicited unexpected reactions from the islanders. Deprived of the sound of any musical instrument, they began to dance frantically during an episode described by Rallier du Baty as a joyful frenzy.
Loïc Damm, University of Montpellier and Benoit Bardy, University of Montpellier
This episode serves as a reminder that music is more than just a cultural phenomenon—it is literally hardwired into us. And we still don’t fully understand the true extent of its influence.
Music encourages us to move, and we are able to synchronize our movements with its rhythms—a natural and universal tendency. The most prominent rhythmic element that we identify and use to guide our movements is the beat. The frequency of the beat defines the musical tempo.
Tapping, moving in time to the beat, or of course dancing are activities that may seem trivial, yet they rely on an essential ability: coordinating our body’s movements with regular, predictable auditory rhythms. This is known as the coupling of perception and action.
When it comes to synchronizing movement with the rhythm of the music, timing is essential. Imagine a dancer’s choreography: you expect the music and movement to be in sync. In other words, the frequency of the movement and the tempo of the music must align.
But that’s not enough. For their timing to be perfect, the music and movement must also be perfectly in sync: any misalignment is immediately noticeable. Imagine, for example, a musician playing behind the rest of the orchestra…
Linking perception and action
To synchronize our movements with the beat of the music, we need to perceive the rhythm accurately. This is actually far from straightforward: the wealth of rhythmic information in music still eludes even the most sophisticated specialized algorithms… And we’re not all on equal footing in this regard; our musical training, in particular, influences our ability to perceive and synchronize.
The interpretation of musical rhythms relies on a vast network of brain structures studied through neuroimaging. Several regions respond to and interact with the presence of a beat: some typically classified as predominantly “sensory” (such as the auditory cortical areas of the temporal lobe), and others as predominantly “motor” (such as the basal ganglia or the premotor and motor areas of the frontal lobe). They are involved in both the analysis and perception of rhythm.
But they are also activated when a movement is performed in time with an auditory rhythm…just as they are when there is no movement, in a simple perception task.
The traditional view of specialization in different areas of the brain—specifically the sensory and motor areas—thus tends to fade when it comes to perceiving a rhythm or moving in response to it.
Movement triggered by auditory stimuli is an example of sensorimotor coupling or perception-action. It can be described as the strengthening of connections between distinct brain regions, ranging from those that extract the temporal characteristics of auditory information to those that execute movement sequences.
Rhythms throughout our bodies
The range of human movement is broader than is commonly recognized, and it is rhythmic even in the absence of auditory stimuli. In fact, it extends from the voice to walking and running, encompassing virtually all forms of the most creative bodily movements.
Speech production is less intuitive; it actually relies on the activation of muscles that cause our vocal cords to vibrate, creating a distinctive rhythmic pattern! We become aware of this during a monotonous, sleep-inducing speech…
The most obvious form of rhythm is that of locomotion, which is likely the most widely preserved rhythmic physical activity among animals—including Homo sapiens. Walking consists of a simple alternation of left and right steps, achieved through the coordinated activation of the muscles in our legs.
Furthermore, our body’s anatomy, the length of our bones, and the distribution of our body mass limit the frequency of our movements, just as the characteristics of a pendulum determine the interval between the ticks of a clock. In biology, cycles, such as the walking cycle, are maintained over time by a combination of passive (mechanical) and active (muscular) mechanisms.
To achieve this delicate balance, proper muscle coordination appears to be an essential function of the entire nervous system. Bipedal locomotion alone, given the number of muscles involved, is a fascinating demonstration of their mastery of rhythms. This is illustrated by the existence, in vertebrates, of neural networks (called spinal locomotor networks) capable of generating patterns of muscle activity—that is, the coordinated activation of a set of muscles: such patterns result in structured movements such as walking.
Our brain acts as a filter between the body’s internal and external rhythms
Our brain also acts as a filter between our body’s rhythms and those of our environment.
Its ability to analyze a musical rhythm and extract its beat opens up the possibility of using that beat to provide a reference point for our movements by “injecting” it into the relevant areas of the brain.
However, in order to make their way through our musculoskeletal system, external stimuli must meet certain criteria. And this is where mechanics and neurophysiology come into play.
The stability of our own rhythms effectively determines the conditions for potential locomotor training: a musical tempo can only influence us if it is close enough to our walking pace. In this case, and provided there is an interaction between locomotion and music (for example, of a mechanical or neurophysiological nature), our pace will converge toward the tempo of the music: we are drawn in, and synchronization occurs.
When we consider the rhythm of our movements, our brain shows a natural preference for a tempo of around 120 beats per minute. Our walking, for example, is characterized by 70 to 130 steps per minute. In rats, however—which are smaller and walk at a faster pace—it is still auditory stimuli at 120 beats per minute that are most likely to have an influence. The optimal tempo for synchronizing with music may therefore depend on neurobiological constants that are conserved across species.
Rhythm: A Principle of the Brain’s Functional Organization
As early as the19th century, the naturalist Charles Darwin asserted that “the perception, if not the enjoyment, of musical tempo and rhythm is probably common to all animals, and undoubtedly depends on the common physiological nature of their nervous systems.” The idea that the mechanisms associated with this perception may have been preserved throughout evolution fits well with the notion that rhythm, just as it is a fundamental aspect of musical structure, is a principle of the brain’s functional organization.
Thus, while our species is capable of a unique form of voluntary, rhythm-based predictive synchronization, rodents already possess a capacity for spontaneous synchronization that could be considered an evolutionary precursor—less developed, to be sure, but already present. Without this capacity, we would not be able to produce the melodies that speak to us so viscerally.
The combination of neuroscience and movement science has recently led to a better understanding of how the brain functions when exposed to musical stimuli. As we have seen, these stimuli activate brain regions associated with movement, which in turn contribute to our perception of them: our ability to analyze musical rhythms is thus enhanced by movement: a coupling between perception and action that allows us to interact more effectively with our environment. We are even capable of extracting musical beats—the basic unit of rhythm—from the sounds we hear, enabling us to use music to guide our movement by synchronizing with it.
We are only just beginning to understand how pervasive these phenomena of synchronization are in our daily lives—whether we’re applauding in unison at the end of a performance or spontaneously matching our pace to that of the people around us in a crowd… It is up to science to objectively assess their impact, just as it has done with music… The fields of study related to social interactions, cognition, and many others are far from exhausted!
Loïc Damm, Postdoctoral Researcher, University of Montpellier and Benoit Bardy, Professor of Movement Sciences, founder of the EuroMov center, member of the Institut Universitaire de France (IUF), University of Montpellier
This article is republished from The Conversation under a Creative Commons license. Readthe original article.