There are some songs which are stuck eternally and no matter how hard you try, you can never get it off your brain. It doesn’t really matter if you are a music fanatic, we are exposed to a variety of music in our daily lives. Watching a television or listening to radio, walking down the road or listening to people humming, we catch music pretty fast. Once you do that, the music in your head pops up without any warning and we can’t help singing to ourselves.
This phenomenon, called involuntary musical imagery (INMI), or more colloquially “earworms,” is a common experience, but people with certain personality traits such as neuroticism may experience it more so than others. While this much was known, its neural basis was a mystery, but a new study has finally offered us some insight. According to the findings, its frequency seems to be linked to the thickness of brain regions involved in musical imagery, or the ability to imagine absent sounds. Furthermore, its occurrence and processing seems to be associated with areas involved in emotions and memory.
For the study, researchers enrolled 44 healthy male and female participants ranging in age from 25 to 70. None of the volunteers had a history of neurological damage or hearing loss, and none were expert musicians. After completing a survey about their personal INMI experiences, including frequency and whether it can help with everyday activities, and their engagement with music so that differences in musical backgrounds could be controlled for, the researchers imaged their brains using an MRI machine. In particular, they were looking for morphological differences, such as greater volumes of brain tissue, which were associated with INMI.
Scientists found a correlation between INMI frequency and cerebral cortex (cortical) thickness in two brain regions: the right Heschl’s gyrus (HG) and the right inferior frontal gyrus (IFG). Interestingly, the former has previously been linked with auditory perception, or how our brain interprets the sounds we hear, and voluntary musical imagery, the conscious version of INMI. The latter, on the other hand, is thought to be involved in our memory of pitch.
Surprisingly, they actually found that people who displayed reduced thickness in the right HG tended to experience INMI more frequently, which doesn’t fit in with research in which musical experts tended to have thicker cortices than non-experts. A negative correlation was also observed for the right IFG, but this makes sense because this brain region plays inhibitory roles in the brain and thus may reduce spontaneous activity in other areas. So if the area is reduced in thickness, then its inhibitory action may also be reduced, thus increasing INMI frequency.
Researchers managed to conclude that “INMI is a common internal experience recruiting brain networks involved in perception, emotions, memory and spontaneous thoughts.”