The Neuroscience of Meditation
Understanding the default network may eventually elucidate information about the mental diseases that seem to target it, including Alzheimer’s, autism and depression. While the activity of the external network is sometimes also affected in these diseases, it is “not nearly as broken,” says Jessica Andrews-Hanna, who recently completed her graduate studies in the laboratory of Randy Buckner at Harvard University on the default networks of aging people.
The diseases that involve the default network are varied but, for all of them, the network does not seem to turn off when it should. Perhaps because it loses that “push-pull” relationship with the external network in patients with severe Alzheimer’s and other cognitive problems, it remains perpetually “on.” Within the default network, activity is disorganized and connections are deteriorated. Its activity also does not seem to wane in studies of autistic people when they perform goal-related tasks, or of depressed people during rest.
All these studies suggest that there could be a striking similarity between the brains of meditators and those of people with dementia or depression. According to Andrews-Hanna, if it’s true that meditators maintain their two networks operating at the same time, their brain scans would be reminiscent of those of the mentally ill. “Presumably, in the meditators’ case, maybe it’s all cognitive; maybe they have the ability to say, ‘Now I want to control these two [networks] together,’” says Andrews-Hanna. “If you can turn the brain regions on and off when you want, that’s great.”
For now, neuroscientists are waiting to learn what Josipovic and Heeger find from their studies of meditators, which they hope will offer unique insight about the default network. The first step is to see if nondual contemplation — combining the external and subjective experiences — does correspond to differences in the default network. If it does, these studies will open up a new way to explore what was before a completely elusive network.
