Presentation

Hyun-Woong Kim¹, Jessica Kovar¹, Jesper Bajwa¹, Yasir Mian¹, Yune S Lee¹; ¹School of Behavioral and Brain Sciences, The University of Texas at Dallas

Introduction: Previous research has shown that the ability to discriminate musical rhythms predicts grammar proficiency in children (Gordon et al., 2015; Lee et al., 2020). Here, we investigated genetic factors mediating the relationship between multiple rhythm and grammar skills in adults. Methods: A total of 132 participants aged 18-37 years (mean: 20.2 years; 70 females) underwent an array of behavioral tasks measuring rhythm, grammar, and working memory skills. In the rhythm tasks, participants listened to a pair of rhythm sequences and decided if they were the same or different (rhythm discrimination), tapped their index finger consistently at their most natural and comfortable tempo (spontaneous tapping), and tapped along metronome beats at 36, 53, 80, and 120 beats-per-minutes (auditory beat tapping). In the grammar tasks, participants decided if each spoken sentence was grammatically correct (grammaticality judgment), and identified the gender of the agent in spoken sentences varying in syntactic complexity (i.e., subject- vs. object-relative) (sentence comprehension). In the working memory task, participants heard a sequence of alternating numbers and letters and subsequently repeated them back in numerical and alphabetical orders. After the behavioral tasks, participants were genotyped for the DRD1, DRD2, and COMT polymorphisms. Results: Partial correlation analysis revealed that higher spontaneous and auditory beat tapping consistency predicted higher sentence comprehension and grammaticality judgment accuracy even after working memory being controlled. The results indicated a double dissociation between rhythm and grammar skills. That is, when further controlled for each other, spontaneous tapping correlated only with grammaticality judgment whereas auditory beat tapping correlated only with sentence comprehension. We also found that higher rhythm discrimination accuracy predicted better sentence comprehension and grammaticality judgment performance. Critically, the correlation between rhythm discrimination and grammar performance was more pronounced in DRD1 G/A alleles than DRD1 A/A or G/G. Conclusion: Together, our findings demonstrate (1) that internal (i.e., spontaneous tapping) and external (i.e., auditory beat tapping) rhythm abilities play distinct roles in predicting individual differences in grammar performance and (2) that the relationship between perceptual rhythm and syntax processing is dependent on genetic variations (i.e., DRD1) affecting the dopaminergic system in the basal ganglia.

Topic Areas: History of the Neurobiology of Language, Writing and Spelling