mercoledì 16 ottobre 2013

Neurotheology: Teasing Out the Benefits of Meditation

From: Dana Web Site - By Carl Sherman

September 10, 2013

The human brain is nature’s masterwork: From this highly organized lump of tissue emerge the wizardry of science and sublimity of art.
Too bad it can’t control itself. That same brain all too often torments its owner with unspeakable anxiety, suicidal sadness, and addiction to destructive chemicals, which the best efforts of psychiatric science and the psychotherapeutic arts can relieve with only limited success.

Recent advances in neuroscience offer glimmers of progress toward this elusive goal. With real-time fMRI [rtfMRI] neurofeedback, a mix of cutting-edge technology and fundamental behavioral principles, people have learned to self-regulate brain function in ways that, at least transiently, reduce anxiety and raise mood. [See The Promise of Neurofeedback]
Another highly active area of brain research suggests that a different path might lead to similar ends: meditation. In most of its varied forms, this age-old approach to self-mastery promotes increased awareness of and control over one’s mental activity. 

Originally a spiritual practice, meditation has now been adapted to clinical purposes. 

Mindfulness meditation, in particular, has proven helpful for a variety of mental maladies.
“Meditation can be thought of as a form of biofeedback, a very old-fashioned form, where people have insight into their feelings and mental states, self-reflect and use that as feedback,” says Michelle Hampson, assistant professor at the Yale Magnetic Resonance Research Center, an expert in rtfMRI who recently collaborated in a meditation study.

How meditation trains the brain?

The practice, simple as it sounds, appears to be powerful: Research in the past decade has offered compelling evidence that meditation changes the brain in many ways. [Richard  Davidson of University of Wisconsin,  a pioneering researcher in this field, reviewed  a number of these studies in a 2012  paper in NatureNeuroscience. ]
“In a young field you start with simple, cross-sectional comparisons of structure, then move toward longitudinal change,” says Britta Hölzel, of Massachusetts General Hospital and Harvard University. As in neuroscience generally, she says, “the trend is away from simple comparisons to more complex network analysis—functional connectivity.”
Hölzel’s earlier work showed structural differences between the brains of long-time meditators and controls, and also demonstrated changes—increased gray matter in areas involved in emotional regulation and other cognitive functions—after just weeks of meditation training. [Psychiatric Res. 2011, 191(1): 36-43].

In some of her subsequent research, “I’ve become more interested in functional imaging,” she says, “and in trying to understand the relation of brain changes to behavioral variables and well-being. We know from clinical research that Mindfulness Based Stress Reduction (MBSR) is very successful in improving symptoms, but not much about the mechanisms underlying that improvement.”
She recently investigated that question in people who had generalized anxiety disorder, the “worry disease” that, earlier research has shown, often responds well to mindfulness-based treatment. In a study reported in a 2013 issue of NeuroImage: Clinical, she used fMRI to compare brain function in subjects who had 8 weeks of MBSR,  and those who had a program of basic stress management education without meditation.
Participants who went through the MBSR program had measureably lower levels of anxiety than those who had stress management education  (both groups showed some reduction). There were changes in brain function, too: During an anxiety-inducing exercise, activity in prefrontal regions increased after MBSR training, and connectivity between prefrontal areas and the amygdala increased as well. The bigger the increase, the bigger the reduction in measures of anxiety.  
“I would think the change in functional connectivity fits in with changes in emotional regulation: People gain a different approach toward their own emotions” after MBSR, Hölzel conjectured.
Other researchers have been drawing similar connections between symptom reduction and brain changes after meditation. A special issue of Social Cognitive and Affective Neuroscience devoted to “Mindfulness Neuroscience,” for example, included studies of neural changes related to improvements in depression, social anxiety, and tobacco craving.  

Neurofeedback meets meditation?

For a more detailed look inside the meditating brain, some researchers have turned to real-time fMRI. “This type of technology can show us moment-to-moment how subjective experience lines up with increased and decreased neural activity,” says Judson Brewer, medical director of the Yale Therapeutic Neuroscience Clinic.
In a study reported online in NeuroImage in May 2013, Brewer and colleagues found that meditators’ description of self-reflection during meditation—how the mind focuses on an object, wanders off, then returns to the task—closely corresponds to activity in the posterior cingulate cortex (PCC), a part of the brain associated with self-referential thinking.
What was more, when the subjects watched readouts of their brain activity, experienced meditators (but not novices) were able to increase or reduce activity in the PCC at will—much as subjects who had undergone rtfMRI neurofeedback might have done. “Meditation is, in effect, training in altering that brain region. For meditators, it was confirmation of what they were already doing,” says Brewer.
Britta Hölzel sees the use of rtfMRI neurofeedback as “a nice complement for understanding the function of brain areas, and how this and our behavioral experience are related…. a way to gain more understanding of brain processes in meditation.

“[This study] was able to demonstrate directly how experienced meditators are better able to regulate their own brain function, beyond subjective report or attentional path.”
Hölzel sees the possibility of wider applications of rtfMRI in meditation research, including, perhaps, some aspects of her own work. “I’m attempting to understand functional connectivity findings better. rtfMRI is feasible for us in our institution, and would be a good potential way to get at that.”
In pragmatic terms, probing moment-to-moment brain activity with rtfMRI could make meditation training more efficient, Brewer says. “We could use brain readouts to test what instructions are easier to follow.”

Along these lines, Michelle Hampson conjectured that neurofeedback might be used to tailor training to the individual, “allowing subjects to figure out what works best for them in a reasonable time. Say, group studies found that three different kinds of instruction were helpful in learning to meditate. A person could try each, and see right away what happens in terms of brain circuits, even before they became aware of getting into a meditative state. The potential for personalization is promising.” 

Might a further step be to combine old and new modes of self-regulation for more potent therapeutic effects? 
Brewer’s group has received an NIH grant to study that possibility. “The aim is to see if rtfMRI neurofeedback can augment MBSR training,” he says. “One group of subjects will get eight weeks of MBSR alone, another group will receive it plus neurofeedback, and a third will have sham neurofeedback. We’ll compare how well they can learn MBSR.”
But even if rtfMRI neurofeedback were to prove an effective adjunct to meditation training, cost would be a major obstacle, observes Yi-Yuan Tang, director of the Texas Tech University Neuroimaging Institute. “It may not be practical [outside of the experimental context] … no one can pay for time in the scanner.”

EEG neurofeedback, an older but less precise measure that tracks electrical activity to monitor brain function, may offer an alternative. “Some people have had good experience in using that,” says Hölzel. “It’s more feasible and affordable.” (In fact, programs promising to aid meditation training with EEG are commercially available, although their validity hasn’t been proven.)

As research tools to deconstruct cognitive states like meditation, EEG and rtfMRI neurofeedback may ultimately be complementary, suggests Tang. "fMRI has very good spatial resolution, EEG good temporal resolution. Many people are thinking about combining them to get more precise information about real-time brain activity.”

Nessun commento:

Posta un commento