Thursday, 17 October 2013

EEG profiles of meditation categories--Travis and Shear

Travis and Shear (2010) point to the potential usefulness of brain patterns as an objective language to discuss procedures and experiences resulting from different meditation practices.  They distinguish three categories: the two commonly accepted categories of focused attention (FA) and open monitoring (OM) meditation and a third category of automatic self-transcending (AST?).  They claim that different meditations can be assigned to these categories based on their eeg profiles.

The FA category is for meditations that involve staying focused on a given object and returning attention to it when the mind wanders.  The OM category is for meditations that involve non-reactive moment-to-moment monitoring of the content of experience.  The AST category is for meditation techniques “designed to transcend their own activity.”

They hypothesize that FA meditations would be characterized by increased activity in the gamma (30-50 Hz.) and beta2 (20-30 Hz.) bands because these bands are associated with highly focused attention to a specific object in the experiential field.   Beta1 (13-30 Hz.), which is associated with creating unity in our experiences, would be found in meditations in all three categories.  Posterior alpha2 (10-12 Hz.) activity should be increased in any type of sitting meditation in which the eyes are closed, since this band is associated with cortical idling.  Alpha1 (8-10), which appears to index level of internalized attention, alertness and expectancy,  should be most evident in any meditation that transcends its own activity.  Frontal midline theta (4-8) activity is a neural index of monitoring inner processes and should be most evident in meditation techniques that involve monitoring ongoing experience without high levels of control or manipulation of the contents of experience.  They note that changes in delta band activity have been noted in some studies of meditation, but not consistently.

For the purposes of summary, I will focus on only the most commonly practiced (and researched) forms of meditation that they discuss.  On the basis of their assumptions, they place loving-kindness-compassion meditation and Zen-3rd ventricle meditation in the FA category; Goenka style vipassana and Zen meditation in the OM category; and Transcendental Meditation in the AST category.

Loving-kindness-compassion meditation has been shown to produce relatively high gamma power, and there is a high positive correlation between gamma power and years of practice.  The Zen–3rd ventricle meditation, which involves focusing on a point near the crown of the head, is associated with higher beta2 activity.  Curiously, Travis and Shear do not discuss concentration meditation on the breath, which is probably the most commonly practiced form of meditation, and is usually classified as FA.

In their discussion of OM, Travis and Shear state that they could only find one study of Vipassana mindfulness meditation, and they rely for their discussion on a description of this study by Cahn and Polich (2006).  The technique studied was a Goenka style body-scan meditation.  Comparisons were made between resting and meditation conditions for 16 individuals who had practiced this style of meditation for an average of 20 years.  In this group, posterior alpha power was higher than central or frontal power with no differences in alpha between the two conditions.  Frontal theta increased during the meditation and occipital gamma power was higher.  A study of monks at three levels of experience doing zazen indicated higher levels of frontal midline theta while meditating among the most experienced monks only.

In the context of their discussion of OM, they also discuss studies of techniques that would usually be considered to be in the FA category (a Vedic form of samadhi meditation and a concentrative Qi-Cong meditation).  In studies of these techniques, higher midline frontal theta was also found along with higher theta coherence.

Travis and Shear’s discussion of AST focuses on Transcendental Meditation.  They recognize that other forms of meditation transcend their technique once automaticity is achieved, but they maintain that TM does this most efficiently.  Studies of TM meditators at different levels of experience suggest that they develop higher global alpha power and frontal alpha1 coherence.  Notably for this type of meditation there does not appear to be much difference between novices and expert.  This might be evidence for Travis and Shear’s claim of the efficiency of the technique.  It might also indicate that the technique does not result in progress.

While the idea that meditation techniques can be classified by EEG profile is very appealing, there was not an adequate basis in the studies available at the time that Travis and Shear wrote their article to make a convincing case.  FA with breath focus was not included in their survey, which strikes me as a very serious omission.  The studies included under the category of OM appear quite diverse from body-scan techniques to zazen to concentrative techniques that would normally be classified as FA.

Please feel free to comment or, if you wish, direct questions and comments to me at drampsych@gmail.com.

Cahn, B. R., & Polich, J. (2006). Meditation states and traits: EEG, ERP, and neuroimaging studies. Psychological bulletin132(2), 180.
Travis, F., & Shear, J. (2010). Focused attention, open monitoring and automatic self-transcending: categories to organize meditations from Vedic, Buddhist and Chinese traditions. Consciousness and cognition19(4), 1110-1118.

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