Credit: Malagalabombonera, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons.
Why is it that some music can have us quietly tapping our feet, whilst other tunes can have us going mad in our bedrooms, belting out songs or rocking guitar riffs? Increasingly, scientists are discovering the reasons behind our behaviour when it comes to music. Theories abound, sometimes in conflict and sometimes in agreement, but the reality is the way our individual brains are wired can be part of the answer.
Which leads to something else: can we manipulate an individual’s neurological signals through music? The concept is gaining traction, especially when seeking to help sufferers of neurological conditions such as Parkinson’s. As Concordia University’s Dr Connor Spiech explains, working out why we groove today is helping to shape the treatments of tomorrow…
ScienceVega: What makes us ‘become music’ when we listen to it?
CS: There is a notion called ‘embodiment’ and in this sense, we’re talking about embodiment referring to somehow internalising the music into your body. So this can either be overt by synchronising our body movements to the music, and that can be dancing, it can be tapping your feet or nodding your head to the beat, or it could be singing along.
It can also be covert by our physiology synchronising to the music in some way: often your heart rate variability might stabilise a little bit or it might increase; with respiration, you tend to breathe in phase with important moments of the music; or your brain waves will synchronise to the beat. The music literally gets into your sensory systems, and it synchronises all sorts of body systems. Another covert response is our pupil dilations which can also actually synchronise to the beat of the music. Obviously light has an impact on your pupils, but so does music. When it gets harder to track the beat, your pupil finds it harder to couple to. Pupil synchronisation to the beat gets worse the harder it is to track the music.
All of these little cognitive effects, and they are very, very small, show people synchronising to the beat. They are all examples of covert physiological entrainment with the music, which is what neural resonance theory (NRT) is all about.
Credit: Connor Spiech/ Concordia University.
ScienceVega: What exactly is neural resonance theory?
CS: This is a theory primarily concerned with this physiological embodiment. The idea is that you have natural physiological rhythms inside your body that are going on all the time, so even when you’re not listening to music, your brain waves are oscillating at specific frequencies; you’re breathing at a specific rate; and your heart rate is hopefully going at a healthy 60-70 beats per minute. These physiological rhythms in your body will sometimes resonate to certain rhythms in our environment.
If you think about a wine glass that rings out and vibrates when you sing a specific pitch, or you play a tuning fork near it at that specific pitch, it rings out because that’s the resonance frequency of the glass. This frequency is its natural frequency because of its physical properties which make it ring out and coupled to that same rhythm when it’s exposed to it in the environment.
In this way, our brains are a bit like the wine glass. When we are exposed to rhythms in our environment our brain will react at that frequency too. Typically it is talked about in terms of beat perception. Most people have a preference to move around at about one to two Hertz, which is about 120 beats per minute or perhaps a little slower. That is the same speed we find in a lot of music, so the music itself of resonates within our nervous system and how we are perceiving the beat is through this resonance.
Pupils can dilate to the beat. Credit: Rossche, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
ScienceVega: How can NRT have positive effects on things like Parkinson’s, stroke or depression?
CS: For stroke and depression it is not so straightforward, but for Parkinson’s, there are positive outcomes that we’re already seeing. There is a therapy called rhythmic auditory stimulation (RAS), where you play a metronome, the tempo of which you can alter, and you match it to the participant’s own natural movement rate. You synchronise their walking to the metronome and the idea is that this metronome is inducing a resonance in the brain at their natural frequency for walking, and that this then entrains their movements, which makes the movement less variable.
One of the things with Parkinson’s is that shuffling gait as people walk. They have an irregular step length and walking is not particularly easy, but when they’re listening to the metronome, their step length becomes quite a lot more regularised and they can walk like normal, healthy people.
There are great videos of this on YouTube, and it’s pretty remarkable to see. The problem is that when the metronome stops, the benefits stop. And that leads us onto the question of whether we can use this to train neuroplasticity and almost ‘rewire’ the brain so that it works a little longer even after the sound goes off.
Sufferers of Parkinson’s can show remarkable improvement in their walking when music is played. Credit: rawpixel.com, CC0, via Wikimedia Commons.
ScienceVega: Why are you particularly interested in the impact music can have on our minds and bodies?
CS: I got into music cognition research for the same reason a lot of psychologists get into psychology; because of a selfish desire to understand myself better, and I also play music. After taking more neuroscience classes and getting deeper into the research, music starts to stand out as this really weird sensory experience that has super powerful effects on emotion for reasons that just aren’t as clear as they are in other sensory systems.
It’s pretty obvious why something like smell or taste can lead to very strong, especially negative, emotional reactions; you don’t want to eat rotten food because rotten food can poison you and the emotion serves to discourage you from eating it.
But it is far less obvious why organised sounds out in the environment have this weird ability to make us feel really strongly; feelings of pleasure and making us want to move along to the beat. It’s just weird.
ScienceVega: Why do we get ‘the pleasurable urge to groove’ when we hear music?
CS: That’s been the centre of my research for a while and there are two main theories in the literature that, right now, have answers for it. I don’t think they’re mutually exclusive but others do think they’re in opposition to each other. In line with NRT, the explanation there is resonance. We move to moderately complex rhythms specifically, because that is what our motor systems resonate to the most. I say ‘specifically’, because this is where we still have resonance, but there’s actually not that much there in the music. The beat itself in the music isn’t actually spoon fed to you in the sense that there’s not an event happening on every single beat location. Somehow, we’re still actually able to find the beat despite the beat not being contained entirely in the sound itself.
This is where movement seems to happen. You get resonance here, but you don’t get it at low complexity because it’s already in the sound. Your auditory system is entrained, but your motor system isn’t entrained. With moderate levels of rhythmic complexity, the motor system almost ‘comes online’ to help the auditory system find the beat because it’s not inherent in the sound. At high levels of rhythmic complexity, there’s no beat to move to, or to resonate to, so you can’t find the beat.
The other explanation is a theory called ‘predictive coding’, which again is getting at the same thing. It suggests that at low levels of rhythmic complexity, it’s too simple and it’s too predictable, so you don’t want to move to it. At high levels of rhythmic complexity, it’s too unpredictable and you can’t move to it. But at moderate levels of rhythmic complexity, you still know where the beat is, and then you’re using your movements to actually reinforce where you think the beat is.
A lot of music falls into the moderately complex kind of category, but you do find really complex music that people don’t really want to move to; some types of really avant-garde music don’t have a really strong beat, and because there is no beat, it makes it unpredictable as to when you should be moving. When you don’t know when you should move, then you don’t move to that kind of music.
Similarly for nursery rhymes and lullabies – the rhythm is so simple that you don’t really find yourself moving along to it that much. But it’s aimed at very young kids in their very early development and the reason why these babies and young kids like this kind of music is because their nervous system isn’t as developed. Their timing abilities aren’t as good as adults, but they can still get the music.
The reason why these babies and young kids like lullabies is because their nervous system isn’t as developed as an adult’s.
ScienceVega: How do different types of music impact on that urge to groove?
CS: Moderate rhythmic complexity seems to be that sweet spot that gets everybody to want to move. But what somebody thinks is moderately rhythmically complex is going to vary from person to person. Some people might move to jazz because they have a lot of experience with jazz; they know when the syncopations are going to occur. Whereas for others who don’t listen to a lot of jazz, the music is going to sound very chaotic. That’s a big part of why we all differ.
Some of my colleagues have shown that the two biggest things that make people want to move the most is, firstly, the music being from a genre that they like, and secondly, the music that they are familiar with. Intuitively this makes a lot of sense. Genre preference and familiarity both imply that you probably already know how to move to that kind of music, which seems to be a prerequisite for wanting to move to it.
ScienceVega: Do we ‘groove’ because we are in tune with a particular music or band, or is it because over time we in effect ‘train’ ourselves to like that sound?
CS: It’s probably both, and this is one of the big questions in the literature. Predictive coding definitely favours the latter explanation where you know you like a kind of music because you’ve previously been exposed to it. Through pure statistical learning, being shown the same thing over and over again, you like it more and you want to move to it more and this is what you become engaged with.
Neural resonance theory takes the opposite approach in that because of the way our bodies are innately wired makes us predisposed to like a particular type of music. They also have some flexibility in terms of learning to like new music too. Those internal oscillations in your body, we think, are quite flexible. And so the natural frequency of those can change with a lot of exposure.
ScienceVega: Why do people synchronise their movements more easily to rhythms with tempi closer to their preferred motor rates?
CS: This is a classic example of why neural resonance theory is so compelling. These preferred motor rates are thought to reflect your brain’s internal oscillations, and they are natural rates of oscillation specifically in the motor system. The idea is that tempi that are close to your preferred motor rate more effectively induce this neural resonance that then guides your movement.
It’s as though the rhythm is tapping into your brain’s natural resonance frequency in the motor system. It might explain tempi preferences and certain genres of music are associated with different tempos. For example drum and bass is really fast, so you could imagine somebody with a very high preferred motor rate might like faster music such as drum and bass.
But people don’t always listen to music that matches their current mental state – they also listen to music to deliberately change their mental state. We use music like medicine in that way. If you go to the gym when you’re tired, and you don’t really want to work out, what kind of music are you going to put on? Are you going to put on a lullaby to match your tired mental state or are you going to put on something upbeat to get your energy levels up?
Music has the ability to synchronise with our bodies. Credit: Sascha Kohlmann, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons.
ScienceVega: Where would you like your research to take you next?
CS: That’s a great question! I’ve got a lot of projects in the mix right now, but my main lines of research are looking at how movement itself supports and reinforces beat perception.
We are using magnetoencephalography, where a magnetic coil goes on your head and measures the tiny magnetic field changes from your brain activity, which runs on electricity. That’s nice, because magnetic fields don’t get distorted so much when they’re leaving the skull, whereas electricity does. Magnetoencephalography is sort of like a better version of electroencephalography, which is measuring the electric changes in brain activity in the head. We are using that to look at where in the brain some of this rhythm processing is happening and see how the brain synchronises with different kinds of rhythms.
We are also using transcranial magnetic stimulation where we put a magnet on people’s heads and if we induce a really quick changing magnetic field, we can actually induce electrical activity inside the brain without having to go into the head or run electricity directly into the head. That way we can disrupt or induce certain kinds of brain activity in certain small patches of brain tissue.
