Beat deafness

Beat deafness is a form of congenital amusia characterized by a person's inability to feel musical rhythm or move in time to it.

Generally, humans have the ability to hear musical beat and rhythm beginning in infancy. Some people however, are unable to move in sync with the beat and rhythm of music, suffering from what is known as beat deafness. Beat deafness is a newly discovered form of congenital amusia, in which people lack the ability to perceive or “hear” the beat in a piece of music. Unlike most hearing impairments in which an individual is unable to hear any sort of sound stimuli, those with beat deafness are generally able to hear normally, with the exception of beat and rhythm in music. Those with beat deafness are also unable to dance in step to any type of music. Even people who do not dance well can at least coordinate their movements to the song they are listening to, because they can easily keep time to the beat.

It is estimated that about 4% of people in Western Europe and North America are beat deaf. The first reported case was of a Canadian graduate student, whom researchers have identified as “Mathieu”. Phillips-Silver et al. (2011) examined the human ability to recognize musical beat in a sample of individuals who had had no previous musical training in their lives. The researchers presented a series of songs from different genres and the participants were instructed to simply bounce up and down to the beat of the music. Results indicated that all participants except for Mathieu were able to move in sync with the beat of the music. The researchers also presented video clips which showed a person dancing to music. Mathieu could not identify when the person was or was not dancing in time to the music. Other participants demonstrated no problem with this task.

When sound waves reach the ears, the energy they contain is converted into electrical signals, which are sent via the auditory nerves to the brain. Sound processing begins when these electrical signals reach the primary auditory receiving area in the core part of the temporal lobe. Signals then travel to the area surrounding the core, known as the belt area, and are then transmitted to the parabelt area, which is located next to the belt. Simple sounds such as pure tones are able to activate the core area of the brain, but both the belt and parabelt areas are activated by only complex sounds, such as those found in speech and music. The auditory cortex in the left hemisphere of the brain is responsible for processing beat and rhythm in music. The right auditory cortex is primarily used in distinguishing between different harmonics, which are simple pure tones that combine to create complex tones.

...
Wikipedia