Earworms, stuck song syndrome, musical imagery repetition, involuntary musical imagery — it is a phenomenon with a number of names, but now researchers have a clue as to the brain regions associated with the condition. A new study by Nicolas Farrugia and other London-based researchers has found that involuntary musical imagery (INMI) is linked to areas of the brain involved in musical imagery and spontaneous cognition.

“To the best of our knowledge, this study is the first to investigate the neural basis of INMI. Our results link several facets of INMI with the variability of cortical structure, providing evidence that the structure of fronto-temporal, cingulate and parahippocampal areas contribute to both the occurrence and evaluative processing of the spontaneous internal experience of music,” they wrote in their study, which was published in the journal Consciousness and Cognition.

The researchers used structural magnetic resonance imaging (MRI) to examine neuroanatomical differences between 44 healthy participants at the Cambridge Medical Research Council’s Cognition and Brain Sciences Unit. The brain scans allowed the researchers to compare the thickness of the cerebral cortex, the folded gray tissue that makes up the outermost portion of the brain, with the self-reported frequency of INMI episodes. Cortical thickness roughly correlates with the number of neurons in that area of the brain.

The frequency of INMI episodes was associated with cortical thickness in the Heschl’s gyrus, the site of the primary auditory cortex in the human brain’s temporal lobe, and the right inferior frontal gyrus (rIFG), a region in the frontal lobe of the brain. Reduced cortical thickness of the right Heschl’s Gyrus was related to more frequent INMI episodes, while greater cortical thickness of the right inferior frontal gyrus was related to less frequent INMI episodes.

The Heschl’s Gyrus has been linked to auditory perception and voluntary musical imagery, while the inferior frontal gyrus appears to have a role in pitch memory, the researchers said. The inferior frontal gyrus mediates inhibitory control and could play in a role in suppressing unwanted INMI episodes, which would explain why greater cortical thickness in this region was linked to less frequent INMI episodes.

The study also implicated the Angular Gyrus and anterior cingulate cortex. Both of these brain regions are part of the Default-Mode Network, “a set of brain areas which are more active when participants are not focusing on a task,” the researchers said. The Default-Mode Network is active when a person is at rest and spontaneous neural activity in the network has been linked to mind wandering and daydreaming.