January 6, 2020Neurology
In 2012, Joyce Hays and Jules Mitchel attended a Symposium on Music, the Brain, Medicine and Wellness in celebration with the 40th Anniversary of the Santa Fe Chamber Music Festival, in Santa Fe, New Mexico. The conference, led by musician scientists, presented the state of the science in: the impact of music on 1) the developing brain, 2) cognition, 3) language, 4) memory, and 5) emotion. The symposium also showed how the use of music can promote healing in patients with serious medical conditions including cancer, neurologic diseases, and developmental disorders, and the influence of music on the well-being of individuals and their communities.
According to an article published in Nature Neuroscience (10 June 2019), a study involving primates suggest that speech and music may have shaped the human brain's hearing circuits. According to the authors, it was found that human brains are more sensitive to pitch, the harmonic sounds we hear when listening to music, than the macaque monkey, one of our evolutionary relatives. The project, Sound Health, is a joint project of the National Institutes of Health and the John F. Kennedy Center for the Performing Arts, and aims to understand the role of music in health.
The study apparently started with a friendly bet between two of the authors when both were working at the Massachusetts Institute of Technology (MIT). One team had been searching for differences between how human and monkey brains control vision only to discover that there are very few, as the brain mapping studies suggested that humans and monkeys see the world in very similar ways. But then, one of the authors heard about some studies on hearing being done by his co-author, who, at the time, was a post-doctoral fellow at MIT.
That is when they both got the idea to compare music perception of humans with that of monkeys. Based on his studies, one of the authors bet that they would see no differences. To test this, the authors played a series of harmonic sounds, or tones, to healthy volunteers and monkeys. Meanwhile, functional magnetic resonance imaging (fMRI) was used to monitor brain activity in response to the sounds. The authors also monitored brain activity in response to sounds of toneless noises that were designed to match the frequency levels of each tone played.
At first glance, the scans looked similar and confirmed previous studies. Maps of the auditory cortex of human and monkey brains had similar hot spots of activity regardless of whether the sounds contained tones. However, when the authors looked more closely at the data, they found evidence suggesting the human brain was highly sensitive to tones. The human auditory cortex was much more responsive than the monkey cortex when they looked at the relative activity between tones and equivalent noisy sounds. According to the authors, it was found that human and monkey brains had very similar responses to sounds in any given frequency range. It was only when added tonal structure was added to the sounds that some of these same regions of the human brain became more responsive. Thus, it was concluded that the results suggest the macaque monkey may experience music and other sounds differently. In contrast, the macaque's experience of the visual world is probably very similar to humans.
Further experiments supported these results. Slightly raising the volume of the tonal sounds had little effect on the tone sensitivity observed in the brains of two monkeys. Finally, the authors saw similar results when they used sounds that contained more natural harmonies for monkeys by playing recordings of macaque calls. Brain scans showed that the human auditory cortex was much more responsive than the monkey cortex when they compared relative activity between the calls and toneless, noisy versions of the calls. According to the authors, this finding suggests that speech and music may have fundamentally changed the way our brain processes pitch, and it may also help explain why it has been so hard for scientists to train monkeys to perform auditory tasks that humans find relatively effortless.