Fig 1.
The continuum of attentional engagement, from the high level of focused attention to more diffuse“open monitoring” or “open awareness” meditation.
The three meditation traditions we chose to include in our study can be placed along this continuum, each corresponding to a different focus of attention. Himalayan Yoga tradition uses a mantra to maintain the attentional focus, Vipassana tradition is primarily an open monitoring practice but the specific form assayed (as taught by S. N. Goenka) incorporates loose focus on the somatosensory awareness aspect and the Shoonya practice as taught in the Isha Yoga tradition is an open awareness meditation practice with no specific object to focus on.
Table 1.
Subject groups mean age and estimated hours of life-time meditation experience.
Number in parentheses indicate minimum and maximum hours of meditation. Symbol ± indicates the standard deviation.
Fig 2.
The first 10 minutes of the meditation block (MED) are considered a preparatory period helping to relax for the meditation practice. Meditators then switched to their specific meditation practice for the last 10 minutes of the block. Control subjects practiced breath watching throughout the whole MED block. For the sake of consistency, we kept the length of the instructed mind-wandering block (IMW) equal to the length of the meditation block. When analyzing the data we compared the last 10 minutes of the MED block to the last 10 minutes of the IMW block. Half the subjects passed the blocks in the order presented on panel A, the other half passed the blocks as shown on panel B.
Table 2.
Mean ratings on subjective reports and score on relaxation and hindrance MEDEQ items after meditation.
“Habitual” stands for the experience participants usually have when meditating at home and “Exp.” stands for their experience during the experiment.
Fig 3.
Spectral decomposition for occipital electrode Oz during the meditation condition in all 4 groups of subjects (CTR is the Control group; HYT is the Himalayan Yoga Tradition group; ISY is the Isha Shoonya Yoga group; VIP is the Vipassana group).
Shaded regions indicate the standard error of the mean. The grey shaded area indicates the region of statistical differences between the groups after correction for multiple comparisons (see Material and Methods). The region around 50 Hz has been blanked out on the plot as it corresponds to line noise and has been excluded from analysis.
Fig 4.
A. Spectral differences in the 60–110 Hz range between the control group and each of the meditator groups with MED and IMW conditions combined. A black dot at a given electrode site indicates significance at p<0.05 corrected for multiple comparisons (see Method). B. Spectral differences in the 60–110 Hz range between the Control group and each of the meditator groups during MED condition only. A black dot at a given electrode site indicates significance at p<0.05 corrected for multiple comparisons (see Method). C. Distribution of individual median 60–110 Hz activity over parieto-occipital electrode for combined meditation and IMW conditions in each group. D Median gamma power over parieto-occipital electrodes for the combined meditation and instructed mind-wandering conditions in the three meditator groups, as a function of log-scaled estimated hours of lifelong meditation practice (skipped Pearson’s r = 0.33, confidence interval (CI) = [0.06 0.53]). The grey shaded area shows the 95% bootstrapped CIs. A red dot denotes an outlier that was left out from the computation of the robust correlation analysis whereas the ellipse surrounds the data points included in it.
Fig 5.
A. Average scalp topography of independent components’ activity corresponding to eye related artifacts. B. Average scalp topographies of independent components’ activity for left and right temporal muscle activity. C. No difference was observed between groups for eye movement independent components’ spectral activity in the meditation condition. D. Pooled left and right muscle ICA components spectral activity for the meditation condition indicate no significant difference between the 4 groups of subjects. E. There is a positive correlation between the 60–110 Hz activity in the components of eye related artifacts and the 60–110 Hz activity recorded over the parieto-occipital electrodes in combined MED and IMW conditions (skipped Pearson’ s r = 0.33, CI = [0.10 0.56]). F. The 60–110 Hz activity in the artifactual components related to eye artifacts do not correlate with meditation experience (skipped Pearson’s r = −0.006, CI = [-0.29 0.30]). In both panels C and D the shaded area around the curves represents the standard error to the mean. In panels E and F the shaded area represents the 95% confidence interval (CI).
Fig 6.
A. Spectral differences in the 7–11 Hz range between the Vipassana group and the control, the Himalayan Yoga and the Isha Yoga groups. A black dot indicates significance at p<0.01 for a given electrode site after correction for multiple comparisons (see Material and Methods). B. Distribution of individual median 7–11 Hz activity over all electrodes during meditation in each group.
Table 3.
Summary of the main results.