Research into plasticity in musicians is still in its infancy, but, already, many of the findings from animal studies have found parallels in studies of musicians. At one extreme, years of musical experience, especially in those musicians who begin training early on, might lead to an increase in grey and white matter volume in several brain regions. These anatomical alterations seem to be confined to a critical period. The fact that, in several studies, a correlation was found between the extent of the anatomical differences and the age at which musical training started strongly argues against the possibility that these differences are preexisting and are the cause, rather than the result, of practising music.