Fibre-specific laterality of white matter in left and right language dominant people

Language is the most commonly described lateralised cognitive function, relying more on the left hemisphere compared to the right hemisphere in over 90% of the population. Most research examining the structure-function relationship of language lateralisation only included people showing a left language hemisphere dominance. In this work, we applied a state-of-the-art fixel-based analysis approach, allowing statistical analysis of white matter micro- and macrostructure on a fibre-specific level in a sample of participants with left and right language dominance (LLD and RLD). Both groups showed a similar extensive pattern of white matter lateralisation including a comparable leftwards lateralisation of the arcuate fasciculus, regardless of their functional language lateralisation. These results suggest that lateralisation of language functioning and the arcuate fasciculus are driven by independent biases. Finally, a significant group difference of lateralisation was detected in the forceps minor, with a leftwards lateralisation in LLD and rightwards lateralisation for the RLD group.

Automated summary

Language is predominantly lateralised to the left hemisphere in over 90% of the population. Research using fixel-based analysis found a consistent pattern of white matter lateralisation, with the arcuate fasciculus showing leftward lateralisation regardless of functional language dominance. In addition, a significant group difference in lateralisation was observed in the forceps minor, with leftward lateralisation in the LLD group and rightward lateralisation in the RLD group.