Researchers have uncovered a link between musical training and how the brain processes language in left-handed individuals. In a study published in the Journal of Neuroscience, left-handed musicians were found to have a higher likelihood of atypical language lateralization, shifting language processing to the right hemisphere. The study identifies two distinct pathways to this phenomenon, suggesting that musical training impacts brain connectivity and structure related to language functions.
Language lateralization, or the tendency for language processing to be localized in one hemisphere of the brain, is typically a left-dominant process in most right-handed individuals. However, left-handed people are more likely to exhibit atypical lateralization, where language functions shift to the right hemisphere.
Despite decades of research, there is still limited understanding of how and why this happens in healthy individuals. Past studies have suggested that factors like interhemispheric brain connectivity may play a role, but there is no definitive explanation.
Musical training is known to alter brain structure and function, particularly in regions associated with auditory and motor control. Since music and language share many cognitive processes, the researchers hypothesized that musicianship might offer clues about the mechanisms behind atypical language lateralization.
“Atypical lateralization of language among left-handers has been known for more than 150 years. Despite this long history, its causes and consequences remain largely a mystery. Given our lab’s previous experience in neuroscience of music, we saw its potential connection to this topic,” said study author Esteban Villar-Rodríguez, a postdoctoral researcher at the Neuropsychology and Functional Neuroimaging research group at Jaume I University.
To explore the relationship between left-handedness, musicianship, and language lateralization, the researchers recruited 112 left-handed or mixed-handed participants, divided into two groups: 56 musicians and 56 non-musicians. To be considered a musician, participants had to have received formal musical training for at least six years.
Both groups were comparable in age and gender distribution, and none had a history of neurological or psychiatric conditions. The participants underwent several neuroimaging tests, including functional magnetic resonance imaging (fMRI) and diffusion-weighted imaging (DWI), to examine brain structure and function.
Participants performed two main tasks: a verb generation task and a word listening task. The verb generation task required them to think of verbs corresponding to presented nouns, a well-known method for assessing language production. The word listening task involved listening to words and tones while the researchers measured brain activity. This helped the team assess how the brain processed language compared to non-linguistic sounds like tones.
Using these tasks, the researchers calculated a “laterality index” for each participant, quantifying whether language processing was more left- or right-dominant. They compared these indices between musicians and non-musicians to understand how brain lateralization differs between the two groups.
The researchers also analyzed the structural connectivity of key brain areas, focusing on the arcuate fasciculus, a white matter tract that links regions involved in language, and the corpus callosum, which connects the two hemispheres of the brain.
The study revealed distinct pathways leading to atypical language lateralization in musicians and non-musicians. In both groups, atypical lateralization was characterized by increased interhemispheric connectivity, but the underlying mechanisms were different.
Among non-musicians, atypical lateralization was linked to underdevelopment in intrahemispheric connectivity, particularly in the anterior arcuate fasciculus. This region is crucial for connecting language-related areas within the same hemisphere, suggesting that in these individuals, the brain’s normal shift from interhemispheric to intrahemispheric control of language may not have fully developed.
In contrast, musicians exhibited enhanced interhemispheric connectivity through the posterior corpus callosum. This suggests that intensive musical training can lead to a different pathway for atypical lateralization, with the corpus callosum playing a key role in transferring information between the hemispheres.
The researchers also found that the more years of musical training a participant had, the more likely they were to exhibit atypical lateralization. Interestingly, musicians who specialized in a single instrument were particularly prone to this pattern.
“Sometimes, the answers to our questions are more complex than initially thought,” Villar-Rodríguez told PsyPost. “Historically, neuroscience has sought a singular explanation for the causes and consequences of atypical language lateralization. However, our findings reveal two alternative pathways—or answers—to this phenomenon, and we have the neuroplastic potential of musical training to thank for this discovery.”
Further analysis showed that individuals with atypical lateralization also demonstrated a mirrored organization of brain activity between language and tone processing. Specifically, rightward dominance in language production corresponded with increased rightward activation in the auditory cortex when listening to speech, and a leftward bias when listening to tones. This pattern was observed in both musicians and non-musicians.
However, the study focused solely on left-handers, so it is unclear whether similar mechanisms are at play in right-handers with atypical lateralization. While left-handers are more likely to exhibit this brain organization, right-handers can also show atypical lateralization.
“Our results are based on a healthy left-handed sample,” Villar-Rodríguez said. “Thus, we can’t be certain how our findings apply to the atypically lateralized right-handed population (which includes approximately 2-4% of right-handers).”
The long-term goals of this research are to gain a deeper understanding of the cognitive effects in individuals with atypical language lateralization and examine its connection to various neurological conditions. “Considering multiple possible pathways to atypical language lateralization might be useful in understanding its role in certain neurological conditions, such as epilepsy, autism, dyslexia, and schizophrenia,” Villar-Rodríguez explained.
The study, “Musicianship and prominence of inter-hemispheric connectivity determine two different pathways to atypical language dominance,” was authored by Esteban Villar-Rodríguez, Lidón Marin-Marin, María Baena-Pérez, Cristina Cano-Melle, Maria Antònia Parcet, and César Ávila.