Abstract
Music processing and right hemispheric language lateralization share a common network in the right auditory cortex and its frontal connections. Given that the development of hemispheric language dominance takes place over several years, this study tested whether musicianship could increase the probability of observing right language dominance in left‐handers. Using a classic fMRI language paradigm, results showed that atypical lateralization was more predominant in musicians (40%) than in nonmusicians (5%). Comparison of left‐handers with typical left and atypical right lateralization revealed that: (a) atypical cases presented a thicker right pars triangularis and more gyrified left Heschl's gyrus; and (b) the right pars triangularis of atypical cases showed a stronger intra‐hemispheric functional connectivity with the right angular gyrus, but a weaker interhemispheric functional connectivity with part of the left Broca's area. Thus, musicianship is the first known factor related to a higher prevalence of atypical language dominance in healthy left‐handed individuals. We suggest that differences in the frontal and temporal cortex might act as shared predisposing factors to both musicianship and atypical language lateralization.
Highlights
Since the postmortem findings from the studies by Broca (Broca, 1861) and Wernicke (Wernicke, 1874), we know that the language function is mainly left-lateralized
As a second part of our study, we aimed to find brain correlates of language lateralization that would support this relationship between musicianship and hemispheric dominance
We suggest that atypical language dominance and musicianship may both arise from specific anatomic and functional characteristics of the brain that enhance the role of the right inferior frontal gyrus (IFG) and right Heschl's gyrus (HG)
Summary
Since the postmortem findings from the studies by Broca (Broca, 1861) and Wernicke (Wernicke, 1874), we know that the language function is mainly left-lateralized (mostly processed by the left hemisphere). The brain bases underlying language lateralization and its modulation in the healthy population have historically been thought to be dependent on structural differences present in the temporal lobe. The logic behind this idea is the marked leftward hemispheric asymmetry present in some temporal regions and the importance of these regions for speech processing (Geschwind & Levitsky, 1968). The pars triangularis of the inferior frontal gyrus (IFG), or Broca's area, has been a focus of lateralization research, with some studies pointing to its rightward asymmetry as a marker of rightward language lateralization (Foundas, Leonard, Gilmore, Fennell, & Heilman, 1996; Josse, Kherif, Flandin, Seghier, & Price, 2009; Keller et al, 2018)
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