From a Yale University press release:

Meditation is known to alter resting brain patterns, suggesting long lasting brain changes, but a new study by researchers from Yale, Harvard, Massachusetts General Hospital, and the Massachusetts Institute of Technology shows meditation also is associated with increased cortical thickness.

The structural changes were found in areas of the brain that are important for sensory, cognitive and emotional processing, the researchers report in the November issue of NeuroReport.

Although the study included only 20 participants, all with extensive training in Buddhist Insight meditation, the results are significant, said Jeremy Gray, assistant professor of psychology at Yale and co-author of the study led by Sara Lazar, assistant in psychology at Massachusetts General Hospital.

EurekAlert: Meditation associated with increased grey matter in the brain