Monthly Archives: March 2010

Neurophysiology of Meditation, 2 of 2

These articles have taken steps to identify and understand physiological differences in well-focused minds compared to lay people, it is analogous to a study showing that professional athletes have more muscle mass, in a manner communicating to those of us who seek to perform better at either a physical sport or become better problem solvers, that the mind, like the body must be trained and shaped to overcome difficult challenges. The papers in these two posts converge in that both studies show meditation increases activity and over long-term practice, cause structural changes in regions associated with focus and concentration.

Fig 1 Larger GM volumes in meditators (co-varied for age). Views of the right orbito-frontal cortex, right thalamus, and left inferior temporal gyrus, where GM is larger in meditators compared to controls. The color intensity represents T-statistic values at the voxel level.

Where the last post attempts to capture a snapshot of the mind during a meditative act the paper in the following post attempts to show structural changes caused by long-term, regular meditation. The underlying anatomical correlates of long-term meditation-Larger hippocampal and frontal volumes of gray matter, by Luders, et al., asked a simple question: does regular meditation over many years cause any neuroanatomical changes in the meditator.

Image from National Geographic magazine

To find the answer the authors took 22 meditators with mean meditation experience of 24.18 years and acquired images of their brains using MRI. The images were then passed through Voxel-based GM volume analysis, at a local and global level. Next the images passed through Parcellated volume analysis software, combined the various software analysis would help to distinguish grey matter volume differences between the 22 long-term meditators and 22 control subjects with no meditation experience. As a result, this would to some degree, help the authors identify regions with grey matter (GM) differences, however it is not so clear how those changes can be specifically attributed to meditation alone. The data in figure 1 reveals increased GM differences in areas shown as activated by meditation in previous studies. The authors believe the results of this study provides enough positive data to continue to examine the relationship between meditation and GM volume, they nevertheless do acknowledge that on a global level there was no GM difference, only on a local level.

The future for neurophysiological research of focus and the clarity of thought relies significantly on better imaging technology; we must be able to see what pathways are becoming activated, when and during which thoughts. With increased complexity in our everyday lives, less time and more tasks to complete, being able to focus on the everyday problems and the overarching issues that are inherent with existence will become more relevant, research such as this may help to aid individuals and societies alike.

Citations:
Luders E, Toga AW, Lepore N, & Gaser C (2009). The underlying anatomical correlates of long-term meditation: larger hippocampal and frontal volumes of gray matter. NeuroImage, 45 (3), 672-8 PMID: 19280691

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Neurophysiology of Meditation, 1 of 2

Fig 1. Expert meditators & non-meditators asked to focus on a dot for extended time. A) 12 expert meditators had greater overlap of increased activation of attention-related brain regions. B) 12 non-meditators had less overlap and activation. Orange hues equal higher correlation between individuals & activation. Blue hues equal little to no correlation between regions of activation.

We have all found ourselves struggling to concentrate on a thought through all the chatter and imagery in our minds. Often, it is a work related problem, other times we try to understand our relationships and throughout our lives we attempt to ponder existence itself. The predicament with focus and the clarity of thought presents itself as an enticing case for study at a neurophysiological level. Meditation as a set of techniques that requires the practitioner to regularly conduct thought exercises or hold steady attention on an internal/external stimuli, can help to identify & understand neural structures implicated in concentration. There are several recent research papers which provide some excellent insight into the contemporary study of how the brain behaves and is ultimately changed through meditation. In Neural correlates of attentional expertise in long-term meditation practitioners by J. A. Brefczynski-Lewis & A. Lutz, et al. the authors scanned the brains of 3 groups as they were asked to concentrate on a dot, using fMRI.  The groups consisted of 16 non-meditators (NM), 11 non-meditators who were given an incentive of $50 if they were able to hold their attention (INM) and 14 expert Buddhist meditators (EM). Furthermore, the EM group was sub-divided into those with most hours of practice, with a mean of 44,000 hours (MHEM) and those meditators with less, mean of 19,000 hours (LHEM);each subgroup containing 4 meditators. Compared to NMs & INMs, EMs were found to have increased activation of attention-related brain regions of interest (ROI), while simultaneously having far less activation of regions unassociated with the task at hand, Fig 1. One of the most interesting results came from the comparison between expert meditator groups MHEMs and LHEMs; whereas LHEMs showed increased activation of ROIs & decreased activation of unassociated regions, MHEMs showed less activation of all brain regions while maintaining the most attention.

Fig 2. Bar graphs for amplitude of activation in the ‘‘early’’ part of the meditation block (the first 10 sec, excluding the first 2 sec because of hemodynamic delay) and the ‘‘late’’ part of the meditation block (120 sec to 200 sec)

What this all means- with a decent amount of practice one can cause greater activation of attention-related regions of the brain, while simultaneously reducing the level of “chatter” and the activation of unrelated brain regions. More interestingly, we see that even amongst expert meditators those with a mean 44,000 hours of meditative practice shows far less activation of all brain regions, including attention related ROIs, compared with meditators who have half as much practice(Fig 2); this demonstrates networks involved in meditation become optimized with increased use, that is it requires less activation, less resources to have the same concentration. Whatever goal one has, having greater focus with more ease will ensure greater success. This paper gives some live data of what is happening in the brain as one performs meditative tasks while showing us that those with extensive practice have a significantly different response, hinting at structural changes. What those changes could possibly be, is discussed in part two of this post.

Citations:
Brefczynski-Lewis JA, Lutz A, Schaefer HS, Levinson DB, & Davidson RJ (2007). Neural correlates of attentional expertise in long-term meditation practitioners. Proceedings of the National Academy of Sciences of the United States of America, 104 (27), 11483-8 PMID: 17596341

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Filed under Meditation, Neuroimaging, Neurophysiology, Neuroscience