Early musical training - sensitive period in brain white matter plasticity

MindBlog has noted a number of studies that document beneficial effects of early music training on adult brain function. Now Steele and collaborators make observations that may partially explain why musicians such as Yo-Yo Ma, Oscar Peterson, and Pablo Casals, who all began training in early childhood before the age of 7 years, are so highly skilled. The authors examine the bundle of nerve fibers, the corpus callosum, that links our two cerebral hemispheres. Playing a musical instrument requires the coordinated action of the two hands and interhemispheric interactions mediated by the corpus callosum have been shown to play a prominent role in bimanual coordination. They measure the connectivity of this nerve fiber bundle using MRI. Edited from their introduction:

...there may be a sensitive period when early musical training has greater effects on the brain and behavior than training later in life...A sensitive period is defined as a developmental window where experience has long-lasting effects on the brain and behavior ...studies in animals show that exposure or training during specific periods in development can produce enhanced structural and functional plasticity in visual, auditory, and somatosensory regions of the brain...Evidence for sensitive periods in humans comes from studies of second language learning showing that early exposure results in greater proficiency, studies of deaf children showing that receiving cochlear implants earlier results in better language development, and studies of blind persons showing greater neuronal reorganization following early blindness.

Musicians are an excellent model for investigating possible sensitive period effects on brain and behavior, as training often begins early and is quantifiable...Evidence for a possible sensitive period for musical training came from a study showing that the anterior corpus callosum (CC) was larger in musicians than non-musicians, and that the difference was greater for those who began training before the age of 7 years...However, none of these studies controlled for the fact that musicians who begin earlier typically have more training than those who begin later.

Here is their abstract:

Training during a sensitive period in development may have greater effects on brain structure and behavior than training later in life. Musicians are an excellent model for investigating sensitive periods because training starts early and can be quantified. Previous studies suggested that early training might be related to greater amounts of white matter in the corpus callosum, but did not control for length of training or identify behavioral correlates of structural change. The current study compared white-matter organization using diffusion tensor imaging in early- and late-trained musicians matched for years of training and experience. We found that early-trained musicians had greater connectivity in the posterior midbody/isthmus of the corpus callosum and that fractional anisotropy in this region was related to age of onset of training and sensorimotor synchronization performance. We propose that training before the age of 7 years results in changes in white-matter connectivity that may serve as a scaffold upon which ongoing experience can build.