The ability to dance to music comes naturally to most members of the human species, and even exists in some species of bird, most famously a cockatoo and YouTube celebrity named Snowball.

But it doesn’t come naturally to everyone.

Researchers from McGill University and the University of Montreal (Phillips-Silver, 2011) have recently published a case study of a student named Matthieu, who not only can’t dance to the beat, but also can’t tell when someone else is dancing asyncronously, although he can dance in time if he is able to watch someone else doing it.

“Mathieu was discovered through a recruitment of subjects
who felt they could not keep the beat in music, such as in clapping
in time at a concert or dancing in a club. Mathieu was the
only clear-cut case among volunteers who reported these problems.
Despite a lifelong love of music and dancing, and musical
training including lessons over several years in various instruments,
voice, dance and choreography, Mathieu complained that
he was unable to find the beat in music. Participation in music
and dance activities, while pleasurable, had been difficult for
him.”

Experimenters put Matthieu and a group of control subjects through a series of tests in which they danced to various types of music. Measurements were gathered by way of a Wii controller (which contains a accelerometer) that was strapped to the trunk of each subject’s body and was able to track and quantify their movements. They also had participants tap their hands to the beat, while not dancing. Finally, they watched videos of someone else dancing (increasingly out of sync) to some Merengue music, and were to asked to identify if the person dancing in the videos was in sync with the music or not.

See the videos here.

Matthieu couldn’t tap a beat in time and the style of music didn’t seem to matter; across numerous styles of music, he couldn’t dance in sync with the groove.*

*He was able to sync himself somewhat to a techno beat, which is basically a glorified metronome but nonetheless slightly more complex.

However, he had no problem locking his movements to the beat of a metronome and could bounce with a consistent tempo without music, while showing normal levels of pitch and tonal perception. He demonstrated normal intelligence, presented no history of neurological or psychiatric disorders and showed so signs of obvious cognitive deficits. It seems Matthieu’s deficit is specific to perceiving the underlying pulse in a piece of music and moving his body to it. In other words, he’s got beat (rhythm) deafness.

Scientists have been aware of the condition for quite a while.

In an Australian Medical Journal from 1890, a surgeon from the Victorian Eye and Ear Hospital in Melbourne described a case of rhythm deafness in a 27-yr. old farmer named W.M.:

(Unlike Matthieu, the farmer’s deficit was much less selective; he also suffered from tone deafness and had severely reduced pain sensitivity)

More recently, Oliver Sacks touched upon rhythm blindness in his book Musiciophilia:

Google and PubMed searches find numerous casual references to “rhythm deafness”, but this does seem to be the first well documented case in the scientific literature. So, if its been talked about for so long but documented so infrequently, how rare is it?

Lead author Jessica Phillips-Silver suggested that it might be as rare as tone deafness, which affects about 4 to 5% of the population. If that’s the case, it could be a real challenge locating enough participants to conduct an fMRI study, which would help reveal the neural regions implicated in the condition. But the research team is confident, in part due to ample press coverage of the paper, that they’ll find more subjects.

So, what might an fMRI study reveal about the condition?

A 2005 study (Brown) examining the neural substrates of dance points to one possibility. In this study, subjects lay in a PET scanner and danced a tango with their legs only, both accompanied by music and free form (without music).



Participants in the dancing-to-music condition showed BOLD activation suggesting that audio-motor entrainment might be mediated through a connection between subcortical auditory areas and the cerebellum. This would make sense give that one of the primary functions of the cerebellum is to coordinate motor actions, particularly precision and accurate timing, by receiving input from the sensory system and integrating those incoming signals to execute fine tuned motor activity.

The authors suggest that the deficit might be primarily perceptual and point to the fact that he failed on a task which did not require body movement, nor does not have any basic motor impairments They also suggest that basal ganglia connections between auditory and motor cortices could play a role, particularly the dorsal auditory pathway leading to the dorsal premotor cortex. Silver and colleagues already have some neuroimaging work underway with Matthieu.

As for future directions, Silver-Phillips said that her group will be looking at exactly what level of musical complexity is required for Matthieu’s beat deafness to emerge. They’re also interested in exploring whether there is any sign of entrainment occurring on a neuronal level, even in the face of the behavioral deficit. In other words, maybe his neurons are dancing to the beat even if he’s not.

References
Phillips-Silver J, Toiviainen P, Gosselin N, Piché O, Nozaradan S, Palmer C, & Peretz I (2011). Born to dance but beat deaf: A new form of congenital amusia. Neuropsychologia, 49 (5), 961-9 PMID: 21316375

Brown, S. (2005). The Neural Basis of Human Dance Cerebral Cortex, 16 (8), 1157-1167 DOI: 10.1093/cercor/bhj057