Changes in Brain Volume and Cognition in a Randomized Trial of Exercise and Social Interaction in a Community-Based Sample of Non-Demented Chinese Elders
“Compared with those in the no-intervention group, participants in the Tai Chi and Social Interaction groups showed significant increases in total brain volume over the intervention period as well as improvements on several neuropsychological measures…
Tai Chi, which has been described as a type of moving meditation [37], requires continuous and sustained attention to maintenance of posture. Although advanced practitioners may be able to carry out the forms without much mental involvement, novices like those in the present study would require sustained attention. The higher level of intellectual involvement in this activity in comparison to walking around a circular course may have been a factor in leading to the disparity of results.”
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3788823/