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More interesting were the differences between the so-called adepts and the novices. In the former, there was significantly greater activation in a brain network linked to empathy and maternal love. Connections from the frontal regions, so active during compassion meditation, to the brain's emotional regions seemed to become stronger with more years of meditation practice, as if the brain had forged more robust connections between thinking and feeling.
But perhaps the most striking difference was in an area in the left prefrontal cortex--the site of activity that marks happiness. While the monks were generating feelings of compassion, activity in the left prefrontal swamped activity in the right prefrontal (associated with negative moods) to a degree never before seen from purely mental activity. By contrast, the undergraduate controls showed no such differences between the left and right prefrontal cortex. This suggests, says Davidson, that the positive state is a skill that can be trained.
For the monks as well as the patients with depression or OCD, the conscious act of thinking about their thoughts in a particular way rearranged the brain. The discovery of neuroplasticity, in particular the power of the mind to change the brain, is still too new for scientists, let alone the rest of us, to grasp its full meaning. But even as it offers new therapies for illnesses of the mind, it promises something more fundamental: a new understanding of what it means to be human.