David Byrne, one of my favorite musicians, is out with a new book that is part-memoir and part-collection-of-essays titled, “How Music Works.” In an excerpt featured in Smithsonian magazine, Byrne explains why sometimes he prefers silence over listening to music–and who can blame him? I’d be pretty tired of hearing artists copping my style for the past 10 years too. But at about a third of the way through, interestingly enough, Byrne switches gears and tries his hand at a little science writing.
Expounding on the neurological basis of how our brains process music, Byrne cites a UCLA study that proposed “our appreciation and feeling for music are deeply dependent on mirror neurons. When you watch, or even just hear, someone play an instrument, the neurons associated with the muscles required to play that instrument fire. Listening to a piano, we ‘feel’ those hand and arm movements, and as any air guitarist will tell you, when you hear or see a scorching solo, you are ‘playing’ it, too.” The mirror neurons to which he’s referring “fire” when an individual performs an action or observes another performing that same action. This has been interpreted to mean that
“when you observe someone performing a movement, particular mirror neurons embedded in your motor system are activated, enabling you to simulate yourself performing that movement using your own motor system. This simulation then allows you to access your own associated intentions, goals, emotions and social values (perhaps through activity of other brain areas including the limbic system) and assign them to the person you are observing.”
Mirror neurons have been implicated as the basis for our capacity to learn through mimicking, our ability to understand and anticipate both the actions and intentions of others. In addition, they are believed to be the foundation of human empathy–much of which is repeated by Byrne throughout the excerpt. Not surprisingly, it has also been proposed that impaired mirror neuron function underlies autism spectrum disorders. More hyperbolically, mirror neurons have also been proclaimed to be “the driving force behind the great leap forward in human evolution.” You’ll have to excuse me, but this is all starting to sound a bit, well, oxytocin-y.
Although it allows him to craft a neat and tidy story, Byrne’s narrow focus on mirror neurons is problematic because it disregards the skepticism surrounding both the existence and importance of mirror neurons. Originally identified in monkeys, mirror neurons have yet to be directly observed in humans, mainly because in order to do so you have to be able to stick a probe into the brain to detect single neurons. The existence of mirror neurons in humans is generally based on measurements of the activity from populations of neurons in functional magnetic resonance (fMRI) studies, which detect changes in blood flow that are correlated with neuronal activity. Regions of the human brain that “light up” in mirror neuron experiments correspond to where scientists have identified mirror neurons in monkeys. But as Dinstein et al. point out, interpreting these fMRI studies is complicated by the fact that other neurons also “light up” in regions of the brain not expected to contain mirroring activity. The best we can conclude from these studies is that there are areas of the brain that look and act like a mirror neuron system.
Even employing different methods that circumvent the limitations of fMRI can prove to be complicated. Adaptation is a counterintuitive process by which the activity of neurons specific for a particular action decreases as that action is repeated. For instance, let’s say there are specific neurons that fire when you drink from a cup. As you drink more and more from a cup the activity from those “drinking-from-a-cup” neurons diminishes. Therefore, the neurons for a specific action can be revealed by looking for the neurons that exclusively lose activity in response to the action being repeated. A 2009 study from Alfonso Caramazza’s lab tried to identify mirror neurons by exploiting this phenomenon. The assumption in this study was that the activity of mirror neurons would “adapt” in response to either the execution or the observation of an action as though they were equivalent. In this experiment, the action being performed or watched was a hand gesture. Adaptation was observed in scenarios where subjects only performed the gesture repeatedly or only watched the gesture repeatedly. Adaptation also occurred when subjects observed the gesture first and then performed it. However, adaptation did not happen when the subject first executed the gesture and then watched it. To Camarazza, these results called into question the existence of mirror neurons. Nevertheless, later in 2009, a study led by James Kilner that used similar techniques yielded conflicting data . This time adaptation was observed when a person performed an action first and then observed it.
Assuming a mirror neuron system does exist, determining its role in the human brain presents a whole different problem. One way scientists test the importance of a component within a system is to remove it and observe the consequences. For instance, you can remove a bike chain and see that without it you wouldn’t be able to pedal the bike. Unfortunately, scientists don’t have the luxury to remove parts of the brain to see what happens. This is where studying individuals with brain injuries or disorders might be informative. As stated before, it has been suggested that mirror neurons play a vital role in our capacity to understand and anticipate the actions and intentions of others. Because one of the features of autism spectrum disorders (ASD) is misunderstanding social cues, it has been hypothesized that this could be due to dysfunctional mirror neurons. In fact, a 2006 study revealed that when test subjects were asked to imitate facial expressions of others, fMRI scans revealed less brain activity in regions associated with mirror neurons in individuals with autism spectrum disorder than in the control group . However, even the links between mirror neuron dysfunction and autism are contentious. A study from 2010, revealed that regions of the brain thought to contain mirror neurons behaved similarly between people with autism and control groups.
Due to both inadequacies in imaging techniques and lack of evidence, the cognitive and empathic roles associated with mirror neurons remain speculative at best. The same can be said about the role of mirror neurons in how our brains process music. Unfortunately, Byrne skimps out on any discussion of this skepticism surrounding mirror neurons. Now, I recognize that as a writer and musician, David Byrne isn’t obligated to express any scientific skepticism. To his credit he at least uses some cautious language (“proposed,” “might explain,” etc.), but absent a healthy dose of skepticism, Byrne gives mirror neurons the appearance of settled science and the sheen of a TED talk. David Byrne remains one of my favorite musicians, but not science writer. Maybe next time Byrne writes about science he’ll hear the alarms of skepticism ringing over his much sought-after silence.
(Thanks to Jerry Nguyen, Justin Kiggins, and Pascal Wallisch for their input and discussion.)
1. Dinstein I, Thomas C, Behrmann M, Heeger DJ. A mirror up to nature. Curr Biol. 2008 Jan 8;18(1):R13-8. Review. Erratum in: Curr Biol. 2008 Feb 12;18(3):233. PubMed PMID: 18177704; PubMed Central PMCID: PMC2517574.
2. Dapretto M, Davies MS, Pfeifer JH, Scott AA, Sigman M, Bookheimer SY, Iacoboni M. Understanding emotions in others: mirror neuron dysfunction in children with autism spectrum disorders. Nat Neurosci. 2006 Jan;9(1):28-30. Epub 2005 Dec 4. PubMed PMID: 16327784.
3. Lingnau A, Gesierich B, Caramazza A. Asymmetric fMRI adaptation reveals no evidence for mirror neurons in humans. Proc Natl Acad Sci U S A. 2009 Jun 16;106(24):9925-30. Epub 2009 Jun 2. PubMed PMID: 19497880; PubMed Central PMCID: PMC2701024.
4. Kilner JM, Neal A, Weiskopf N, Friston KJ, Frith CD. Evidence of mirror neurons in human inferior frontal gyrus. J Neurosci. 2009 Aug 12;29(32):10153-9. PubMed PMID: 19675249; PubMed Central PMCID: PMC278815
5. Dinstein I, Thomas C, Humphreys K, Minshew N, Behrmann M, Heeger DJ. Normal movement selectivity in autism. Neuron. 2010 May 13;66(3):461-9. PubMed PMID: 20471358; PubMed Central PMCID: PMC2872627.
“…there is apparently no empirical result that can falsify the theory. If a mirror neuron shows up in an unexpected place, it is a new part of the mirror system. If a mirror neuron’s activity dissociates from action understanding, it was not coding understanding at that moment. If damage to the motor system doesn’t disrupt understanding, it is because that part of the motor system isn’t mirroring.”