There is limited evidence as to whether meditation is the causative factor for altered brain structure. However, there is a possibility that pre-existing brain heterogeneities could explain these differences. Examinations of meditation-naive persons before and after undergoing brief meditation training in comparison to control groups bare on the edge of causality and indicate that only a few hours of meditation training are necessary to induce neuroplastic changes. The changes in the brain exhibited by those given a brief training have also been observed in almost all the same regions as long-term practitioners.