Music and language. Language and music. These channels of human communication have so much in common - they are auditory, cognitive, vocal, dynamic, social, and multimodal. They are ubiquitous in human societies and an unmistakably diverse and crucial aspect of daily life. Over evolutionary history, language and musicality have been hypothesized to serve some common adaptive functions for communication, parenting, and social cohesion. As a classically-trained singer in my youth (before I trained as a scientist!), I often wondered why I was so obsessed with making lyrics and melodies fit together - why did it feel so natural to combine words and rhythms, including in the foreign languages I was singing in?

Fast forward two decades and the unfolding of my major scientific curiosity: to understand to what extent language and music emerge from common biology. A beautiful subfield has blossomed around questions about perception, learning, production, neural processing, clinical applications, and most recently, inter-individual variability, also termed individual differences. In our new study (Alagöz et al., 2024) in Nature Human Behaviour, we wanted to reimagine the curiosity about shared biological underpinnings of musical rhythm and language skills: this time, from the genomic perspective.

Genomic and neural substrates of rhythm and why they matter for communication

In our 2022 Genome-Wide Association Study of rhythm (Niarchou et al., 2022) we demonstrated that rhythm is highly polygenic: i.e., it is influenced by many independent areas of the genome. We found that a portion of the individual differences in people’s ability to keep time with a musical beat were tied to genetic variation. Detecting, perceiving, and synchronizing to the beat involves complex coordination of auditory and motor functions in widespread brain networks (Kasdan et al., 2022). The coordinated process of beat synchronization is foundational to our interactions with music, and its biological underpinnings. The relevance of these skills is not restricted to musicality: growing evidence shows correlations between individual differences in musical skills like rhythm and language skills like reading (even when you control for factors like education and general cognition; Nayak et al., 2022).

Shared genetic architecture: a putative mechanism for rhythm-language associations

So in our new study, we set out to find whether musical rhythm ability would share some of its underlying genetic influences with language-related traits, as predicted by our theoretical framing of the Atypical Rhythm Risk Hypothesis (Ladányi et al., 2020). The elevated presence of rhythm impairments in individuals with developmental disorders of speech, language, and reading suggested potential shared genetic architecture, but a rigorous test of this hypothesis would necessitate comprehensive characterizations of the genomic basis of language and of musical rhythm. Enter stage: our beat synchronization study published in 2022, which also happened to be a landmark year for the first large GWASs of language traits (Doust et al., 2022; Eising et al., 2022; Rajagopal et al., 2023).

So we joined forces with the world experts on language genetics: Simon Fisher’s Lab at the Max Planck Institute for Psycholinguistics, with work led by outstanding graduate student Gökberk Alagöz. Using data from their prior GWAS of dyslexia plus several other GWASs, we discovered overlap in genetic variation with our beat synchronization (musical rhythm) study.

Positive genetic correlations showed that genetic variants conferring predisposition to more accurate rhythm skills were partially shared with variants conferring predisposition to higher reading-related assessment scores, stronger connectivity of the language network in the brain, and higher grades in foreign language courses. Non-verbal cognition was not genetically correlated with rhythm, suggesting that the results are not simply confounded by general cognitive abilities.

https://www.nature.com/articles/s41562-024-02051-y/figures/1

Interestingly, we also found a positive correlation between rhythm and non-word repetition, a type of task that requires the participant to repeat sequences of nonsense syllables. This result is meaningful because non-word repetition is a great proxy for spoken language skills, and grammatical skills in particular. These genetic results were particularly exciting to me, because the behavioral correlations between rhythm and grammatical skills that we found ten years ago (Gordon et al., 2015) were what got me interested in individual differences and genetics, to begin with! (Happy dance!).

Rhythm impairment and Dyslexia: joint genetic signals and 16 pleiotropic loci

The result showed us that rhythm impairments are genetically correlated with history of dyslexia, a prevalent developmental condition that is characterized by difficulties with reading, spelling, and writing. These findings jived not only with reports from the field at the behavioral level in studies with much smaller sample sizes, but also with our framework from the Atypical Rhythm Risk Hypothesis predicting that rhythm impairment would share genome variation with reading-related disorders including dyslexia. As an aside, keep watching the literature for another upcoming paper using large-scale population health methods, from Srishti Nayak, myself and our team, showing impaired beat synchronization in individuals with a history of dyslexia.

In the current paper, we then generated a new set of genome-wide summary statistics capturing overlapping genetic signal between musical rhythm impairment and dyslexia, with a pipeline adapted for this project by Gökberk Alagöz and Giacomo Bignardi, in which we applied   genomic structural equation modelling to a simple bivariate scenario. The result was a shared genetic factor - the awkwardly-named but biologically-rich “F_gRI-D” (here for simplicity I’ll call it the rhythm-language genetic signal), which allowed us to uncover 16 different genomic loci with shared effects on musical rhythm and language traits. 

The Neurobiological architecture lurking between the genotype and the phenotype.

We were then poised to test this rhythm-language genetic signal for a number of potential neurobiological and evolutionary substrates to understand its biological consequences. On the evolutionary side, we found that the genetic underpinnings of the rhythm-language genetic signal was enriched in genomic regions conserved among primates, and depleted in parts of modern human genomes that are the remnants of Neandertal admixture. We also took first steps to looking at evolutionary characteristics of the rhythm-language genetic overlap, finding that a genetic variant associated with the rhythm-language genetic signal was located on the gene DLAT and showed a distinct evolutionary pattern: this variant was conserved in primates, but diverged on the human lineage. This particular gene also has known links to neurodevelopmental disorders, again reinforcing the primordial links between rhythm, communication and early brain development!

We then explored what type of cells might be impacted by shared genetic variation. What type of brain cells might be important - in adult brain function -  for rhythm and language? Neurons, of course, but focusing for a moment on one of the support cells: our rhythm-language genetic signal was enriched in gene regulatory regions of many neuronal and glial cells, including oligodendrocytes, which play a known role in myelination. That is, oligodendrocytes enable the maintenance of white matter tracts in the brain. And it’s that connectivity that is a key neurobiological aspect of the relationship between rhythm and language.

The connectivity matters, because human brains are special (or nearly so; Cannon & Patel, 2021; Patel, 2021) in their strong connectivity between auditory and motor regions. These white-matter connections are one possible source of co-evolved neurobiological underpinnings of language and musicality. It makes sense, because both music-making and speech require you to coordinate auditory and motor function in a sophisticated way. So we tested a small selection of evolutionarily and functionally relevant white matter tracts in relation to the rhythm-language genetic signal with a method that captures local genetic correlations, i.e., genetic correlations within specific portions of the genome. We focused on the left hemisphere tracts due to their role language processing. These results showed an association on Chromosome 20, where a part of the superior longitudinal fasciculus (SLF-I) white-matter tract is genetically correlated with rhythm-language, supporting the role of key components of the language network in manifesting phonological processing (relevant to speech and reading) and beat synchronization. Those traits could have co-evolved on existing neural architecture for auditory-motor learning, in line with emerging evidence in the field (Patel, 2021). These new results go deeper than the brain by taking us all the way down to the genome and possible evolutionary function.

So, do our genes determine our rhythm and language traits?

 TL:DR - Nope!

Longer answer: genes influence traits, and we see those influences statistically when we look at groups and subsets of people. But when you look at one individual at a time, we don’t have the tools to say if their rhythm and language are directly linked to their unique genetic profile. DNA variation from one individual to another plays a role - an important one - in our communication skills, but our genes are not the end of the story. We know that behavioral traits are influenced by our genes, but rarely are completely determined by our genes. In our Ethical, Legal and Social Implications (ELSI) framework for musicality genomics (Gordon et al., 2023), we strongly discouraged deterministic thinking about genetics. Environment also plays a role!  It’s most accurate to think about the variants on the loci we uncovered here as one factor in our collective neurodiversity: and many factors working in interaction make your brain a little different from the brains of every other human on the planet.

What’s next? The MAPLE framework propels us in new directions

Rhythm is just one part of the larger phenomenon of the roles music plays in society and in our health. As individuals, we vary greatly in all the dimensions of our human musicality (Honing et al., 2015): the myriad ways that we interact with music, encompassing our musical aptitudes/skills/abilities, our musical training and practice, our music listening habits, the emotional reward we derive from music, and more. What does all this have to do with language? Well - we've heard these ideas out in the world: does your "musical ear" help you to learn a second language faster? Do musically trained children have a predisposition for learning to talk more quickly and efficiently? We explored these possibilities and more in our paper by Nayak et al.: the Musical Abilities, Pleiotropy, Language, and Environment framework (MAPLE). Ongoing and future work uses the MAPLE framework to explore the multitude of possible ways that genetic pleiotropy between musicality and language may manifest in the human brain and interact with our environments over the lifespan. This work should give us all something to sing (or dance) and talk about!

Funding

Dr. Gordon was supported by NIH funding under Award Numbers R01DC016977, K18DC017383 and DP2HD098859. A full list of funding for the project is provided in the paper. The funders had no role in study design, data collection and analysis, the decision to publish or the preparation of the manuscript. I appreciate feedback  from co-authors Gokberk Alagöz and Giacomo Bignardi on an earlier draft of this blog post.

References

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