When we listen to music with a catchy and consistent rhythm, we involuntarily blink in sync with the same beat, researchers have found. Accordingly, our eyes automatically react to what our ears perceive. In contrast to intentionally clapping or nodding our heads to the beat of the music, we cannot control or suppress the spontaneous blinking of our eyes during this rhythmic blinking. However, the phenomenon only occurs if we concentrate on the music and really listen.
When we listen to music, we often move to the beat. For example, we can tap our feet to the beat of the radio, nod our heads rhythmically at a concert, clap or dance to it. Some runners also adapt their steps to the music and consciously listen to songs with a certain number of beats per minute while jogging in order to maintain their pace. We can consciously control these and similar movements because our brain can synchronize them with the incoming auditory stimuli. This coordinating mechanism of the brain is called auditory-motor synchronization.
Rhythmic blinking
A team led by Yiyang Wu from the Chinese Academy of Sciences in Beijing has now investigated whether this everyday neurological process also occurs unconsciously. To do this, the researchers analyzed the spontaneous, unconscious blinks of 123 test subjects without any special musical training or talent. At the same time, they played Western classical music pieces to the test subjects at a steady tempo, including chorales by Johann Sebastian Bach – both forwards and backwards. In this way, they ensured that the participants responded to the beat and not to other musical stimuli. While the music was playing, the test subjects were also asked to wait until a red dot appeared on a screen in front of them.
The evaluation showed: The test subjects actually blinked in time. The subjects’ unconscious blinks spontaneously began to synchronize with the music. Their brain waves also involuntarily adapted to the beat of the music, as the team determined using parallel EEG measurements. This was apparently due to the smallest changes in the microstructure of the white matter of the superior longitudinal fasciculus (SLF) – a central nerve connection for sensory and motor signals in the brain. Accordingly, our brain and eyes react involuntarily to what we hear and synchronize with the auditory stimuli via this neural pathway. “We found that people’s spontaneous blinks move in time with the music – even without a request to move – revealing a previously unknown connection between listening to music and the oculomotor system – a tiny action that reveals a deep coordination between hearing and action,” says senior author Yi Du from the Chinese Academy of Sciences.
However, this automatic synchronization of eyes and ears was disrupted by the concentration task. As soon as the participants noticed the red dot, their blinking rhythm no longer matched that of the song. Whether the point appeared earlier or later and with or against the beat of the music didn’t matter, as Wu and her colleagues found. This means that we react to music unconsciously with our eyes, but only when we concentrate on the music. If we are distracted by other things, we no longer blink in time, the researchers conclude.
Application in music therapy and diagnostics
The findings now help to fundamentally understand how neuronal connections in the brain work and how different senses and brain functions interact with one another. This could be useful in music therapy in the future. Some neurological diseases in which body movements are impaired can be treated using auditory-motor synchronization. The more we know about the neural connections between these movement processes, the more effective these therapies become.
In addition, the methodology used could help in the diagnosis of neurological phenomena such as speech disorders or autism: “Since blinks can be easily measured, this behavior offers a simple, implicit insight into how we process rhythms and could one day support the clinical diagnosis of rhythm disorders,” explains Du.
Source: Yiyang Wu (Chinese Academy of Sciences) et al.; PLOS Biology, doi: 10.1371/journal.pbio.3003456