The current dissertation investigated the relationship between brain structure, motor performance, and musical training. Two structural magnetic resonance imaging (MRI) techniques were used: voxel-based morphometry (VBM) and diffusion tensor imaging (DTI). The first study examined the structural correlates of visuomotor synchronisation performance in normal adults. DTI analyses showed that individual differences in synchronisation performance were negatively correlated with white-matter integrity in a region underlying bilateral sensorimotor cortex. Performance was also positively correlated with radial diffusivity in this region, suggesting the influence of a crossing fibre tract. Fibre tractography identified two fibre populations in this region: the corticospinal tract and superior longitudinal fasciculus (SLF). The SLF links parietal and auditory cortical regions previously shown to be engaged during performance of this task in a functional MRI study with the same sample. VBM analyses showed that grey-matter volume in cerebellar regions important for learning was related to the rate of improvement in synchronisation during learning of the task. The second study explored how musical training during early childhood may have long-lasting effects on brain structure and sensorimotor synchronisation performance. DTI was used to compare white-matter structure in three groups: (1) early-trained musicians (ET; before age seven), (2) late-trained musicians (LT; after age seven), and (3) nonmusicians. Groups were also tested on a visuomotor synchronisation task. ET and LT were matched for years of musical training and experience to isolate the possible effect of age of onset of musical training. Behaviourally, ET outperformed LT and nonmusicians on the synchronisation task. DTI results showed that ET had greater white-matter integrity than LT in the posterior midbody of the corpus callosum, a region connecting bilateral sensorimotor cortices. Measures of white-matter integrity extracted from this region correlated with both synchronisation performance and age of onset of musical training. These findings provide evidence that musical training during a potential sensitive period in development can differentially influence white-matter structure and behavioural performance. Our results are consistent with literature supporting the links between individual differences in brain structure and performance, and training and structural plasticity. They suggest that brain structure is the result of interactions between pre-existing factors, developmental factors, and training and experience
