Musical brains: The influence of musical expertise and gender on brain structure and lateralisation

Abstract

A growing literature has identified compelling links between musical expertise and structural and functional alterations in the brain. These are thought to reflect experiencedependent neuroplasticity, arising from the many years engaged in intensive, multi-modal training on a musical instrument, typically from a young age. Related research has identified enhancements of cognitive processes beyond the specific skills trained in music. There is evidence that musicians have enhanced visuospatial abilities, although whether musical training and expertise shapes or influences the neural organisation underlying these general cognitive processes is unknown. The main aims of this thesis were to investigate whether (i) musicians have reduced functional lateralisation of visuospatial processes; (ii) whether altered structural lateralisation, or altered white matter organisation in general, underpins functional and behavioural differences in visuospatial processes in musicians. The effects of gender were also examined, given its known influence on behavioural performance and neural representation of spatial processes. Thirty-three expert musicians and 30 non-musicians underwent functional magnetic resonance imaging (fMRI) while performing three visuospatial tasks: a Landmark task (a variant of a line bisection), 3D Mental Rotation (3DMR), and a Visual Search task. On the Landmark task, gender modulated the relationship between musical expertise and lateralisation: male controls had more strongly right-lateralised activation than female controls, but both male and female musicians were strongly right-lateralised and did not differ from each other. In Study Two, the connectivity of the corpus callosum, superior longitudinal fasciculus (SLF), and corticospinal tract was assessed using diffusion tensor imaging (DTI). Gender once again had a moderating effect in the corpus callosum and the SLF, with differences in white matter connectivity between male and female controls which were not present in musicians. Additional differences between musicians predominantly engaged in instrumental versus vocal training were observed for structural lateralisation of the SLF. Overall these results suggest the neural organisation underlying visuospatial attention, a non-musical cognitive process, was influenced by musical training and expertise, predominantly with a rightward shift in lateralisation in female musicians. The findings underscore the importance of considering moderating variables such as gender and instrument of training when studying the neural correlates of musical expertise.