What mechanisms could contribute to these striking findings? Although speculative at this point, it has been proposed that processes occurring both at the synapse level and at larger scales, including rapid intracortical remodeling of dendritic spines and axonal terminals, glial hypertrophy, and synaptogenesis, might play a contributory role (Draganski and May, 2008, May and Gaser, 2006 and Anderson et al., 1994). Consistently, rapid (within an hour) formation of postsynaptic dendritic spines has been detected in vivo in the pyramidal neurons of the mouse motor cortex following motor training (Xu et al., 2009), and the extent of spine remodeling has been shown to correlate with behavioral improvements

after learning, suggesting that this mechanism of synaptic plasticity may contribute to motor selleckchem memory

formation (Yang et al., 2009). On the other hand, it should be noted that other animal studies demonstrated significant increases in synapse numbers in the rat M1 only after extensive training (Kleim et al., 1996 and Kleim et al., 2004). Slow learning has been linked with structural plasticity in white matter architecture as well (Table 1). Diffusion MRI-based measures, such as fractional anisotropy (FA), are believed to reflect white matter integrity (Fields, 2008), providing HDAC inhibitor a distinctive insight into the microstructural properties of white matter in vivo (Le Bihan et al., 2001 and Mori and Zhang, 2006). Cross-sectional studies, primarily with highly trained musicians, examined white matter correlates of skilled behavior (Bengtsson et al., 2005, Han et al., 2009 and Schmithorst and Wilke, 2002). Fractional anisotropy in the almost posterior limb of the internal capsule, which contains descending corticospinal fibers from the primary sensorimotor and premotor cortices, correlated with number of

practice hours during childhood in skilled musicians (Bengtsson et al., 2005). It has been proposed that these results may reflect experience-induced plasticity during a critical developmental period (Bengtsson et al., 2005). A recent pioneering study provided more direct evidence for experience-induced changes in white matter architecture, resulting from a relatively short period of practice (Scholz et al., 2009). In this study, it was shown that 6 weeks of juggling practice resulted in increased FA in a region of white matter underlying the intraparietal sulcus. Localized increases in gray matter were detected in close proximity to these white matter regions. Yet the magnitude of changes of gray and white matter showed no correlation and developed over markedly different time courses. Interestingly, individual differences in white matter mictrostructure appear to be related to variation in learning (Johansen-Berg, 2010, Della-Maggiore et al., 2009 and Tomassini et al., 2011).