White matter plasticity in the corticospinal tract of musicians: A diffusion tensor imaging study

Abstract

With the advent of diffusion tensor imaging (DTI), the study of plastic changes in white matter architecture due to long-term practice has attracted increasing interest. Professional musicians provide an ideal model for investigating white matter plasticity because of their early onset of extensive auditory and sensorimotor training. We performed fiber tractography and subsequent voxelwise analysis, region of interest (ROI) analysis, and detailed slicewise analysis of diffusion parameters in the corticospinal tract (CST) on 26 professional musicians and a control group of 13 participants. All analyses resulted in significantly lower fractional anisotropy (FA) values in both the left and the right CST in the musician group. Furthermore, a right-greater-than-left asymmetry of FA was observed regardless of group. In the musician group, diffusivity was negatively correlated with the onset of musical training in childhood. A subsequent median split into an early and a late onset musician group (median=7 years) revealed increased diffusivity in the CST of the early onset group as compared to both the late onset group and the controls. In conclusion, these DTI-based findings might indicate plastic changes in white matter architecture of the CST in professional musicians. Our results imply that training-induced changes in diffusion characteristics of the axonal membrane may lead to increased radial diffusivity as reflected in decreased FA values. AbstractWith the advent of diffusion tensor imaging (DTI), the study of plastic changes in white matter architecture due to long-term practice has attracted increasing interest. Professional musicians provide an ideal model for investigating white matter plasticity because of their early onset of extensive auditory and sensorimotor training. We performed fiber tractography and subsequent voxelwise analysis, region of interest (ROI) analysis, and detailed slicewise analysis of diffusion parameters in the CST on 26 professional musicians and a control group of 13 participants. All analyses resulted in significantly lower FA values in both the left and the right CST in the musician group. Furthermore, a right-greater-than-left asymmetry of FA was observed regardless of group.In the musician group, diffusivity was negatively correlated with the onset of musical training in childhood. A subsequent median split into an early and a late onset musician group (median = 7 years) revealed increased diffusivity in the CST of the early onset group as compared with both the late onset group and the controls. In conclusion, these DTI-based findings might indicate plastic changes in white matter architecture of the CST in professional musicians. Our results imply that training-induced changes in diffusion characteristics of the axonal membrane may lead to increased radial diffusivity as reflected in decreased FA values.2

Differential Adaptation of Descending Motor Tracts in Musicians

“…In agreement with previous studies (Toosy et al 2003;Kraus et al 2007;Imfeld et al 2009), we found a right-greaterthan-left asymmetry of FA values in corticospinal motor tracts across all subgroups (see Fig. 2 and Tables 2 and 3).…”

“…Whereas our study complements the work of Bengtsson et al (2005) as well as that of Han et al (2009), differences have emerged between our results and those of Imfeld et al (2009) as well as those of Schmithorst and Wilke (2002), who found lower FA values in musicians relative to nonmusicians. Methodological issues might account for these differences such as the use of a subcortical ROI that included Brodmann Areas 1-4 (Imfeld et al 2009) leading to the inclusion of ascending sensory tracts, whereas our ROIs were defined to only include fiber tracts from distinct primary and nonprimary motor areas; and differences in scanning parameters may have to be considered as well. It is still unclear how diffusivity properties can be interpreted in terms of their underlying white matter structure (Beaulieu 2002;Wheeler-Kingshott and Cercignani 2009).…”

“…Functional specializations and differences in gross-anatomical markers have been demonstrated comparing different instrumental musician groups with each other (Pantev et al 2001;Bangert and Schlaug 2006); however, to the best of our knowledge, they have not been reported for white matter so far. Previous studies have focused on musicians versus nonmusicians white matter differences, but these studies differed in finding either higher or lower FA values within descending motor tracts (Schmithorst and Wilke 2002;Bengtsson et al 2005;Han et al 2009;Imfeld et al 2009). Whereas our study complements the work of Bengtsson et al (2005) as well as that of Han et al (2009), differences have emerged between our results and those of Imfeld et al (2009) as well as those of Schmithorst and Wilke (2002), who found lower FA values in musicians relative to nonmusicians.…”

“…Previous studies have focused on musicians versus nonmusicians white matter differences, but these studies differed in finding either higher or lower FA values within descending motor tracts (Schmithorst and Wilke 2002;Bengtsson et al 2005;Han et al 2009;Imfeld et al 2009). Whereas our study complements the work of Bengtsson et al (2005) as well as that of Han et al (2009), differences have emerged between our results and those of Imfeld et al (2009) as well as those of Schmithorst and Wilke (2002), who found lower FA values in musicians relative to nonmusicians. Methodological issues might account for these differences such as the use of a subcortical ROI that included Brodmann Areas 1-4 (Imfeld et al 2009) leading to the inclusion of ascending sensory tracts, whereas our ROIs were defined to only include fiber tracts from distinct primary and nonprimary motor areas; and differences in scanning parameters may have to be considered as well.…”

“…Previous studies comparing musicians with nonmusicians yielded contradictory results with regard to FA values in corticospinal motor tracts, and none of the studies related diffusivity measures to motor performance measures (Schmithorst and Wilke 2002;Bengtsson et al 2005;Han et al 2009;Imfeld et al 2009). Studies examining neural effects of long-term instrumental music practice have been complemented by studies showing white matter plasticity in response to the acquisition of other nonmusical sensorimotor skills (Scholz et al 2009;Hanggi et al 2010;Landi et al 2011) as well as in response to recovery from neurological disorders (Schlaug et al 2009;Wrigley et al 2009;Lindenberg et al 2010;Granziera et al 2012;Keil et al 2012;Zipse et al 2012) or neural effects of immobilization (Langer et al 2012).…”