Occipital gamma activation during Vipassana meditation

Abstract

Long-term Vipassana meditators sat in meditation vs. a control rest (mind-wandering) state for 21 min in a counterbalanced design with spontaneous EEG recorded. Meditation state dynamics were measured with spectral decomposition of the last 6 min of the eyes-closed silent meditation compared to control state. Meditation was associated with a decrease in frontal delta (1-4 Hz) power, especially pronounced in those participants not reporting drowsiness during meditation. Relative increase in frontal theta (4-8 Hz) power was observed during meditation, as well as significantly increased parieto-occipital gamma (35-45 Hz) power, but no other state effects were found for the theta (4-8 Hz), alpha (8-12 Hz), or beta (12-25 Hz) bands. Alpha power was sensitive to condition order, and more experienced meditators exhibited no tendency toward enhanced alpha during meditation relative to the control task. All participants tended to exhibit decreased alpha in association with reported drowsiness. Cross-experimental session occipital gamma power was the greatest in meditators with a daily practice of 10+ years, and the meditation-related gamma power increase was similarly the strongest in such advanced practitioners. The findings suggest that long-term Vipassana meditation contributes to increased occipital gamma power related to long-term meditational expertise and enhanced sensory awareness.

Fig. 1

The power spectrum for electrode Cz is displayed for both meditation and control states. Grand average scalp maps across states are displayed for each of the major frequency bands so as to indicate scalp topography of the various frequencies

Fig. 2

The scalp maps for delta (1–4 Hz) and gamma (35–45 Hz) bands are displayed with meditation on the left and control task on the right. Both bands showed a statistically significant difference comparing meditation and control states and the scalp map indicating statistical significance is shown below. Statistical significance was determined using bootstrap statistics with false detection rate (FDR) correction for multiple comparison with the threshold significance set at P < 0.05, indicating bilateral frontal decreases in delta power (significant at F3, F4, F7, F8, C3, and C4) and parieto-occipital increases in gamma power (significant at P7, P8, O1, and O2) as meditation state effects. Similar analyses run on the theta, alpha, and beta bands indicated no statistical differences between states at any scalp site and are thus not shown

Fig. 3

Panel A indicates the grand average scalp map for the left and right muscle-independent components, respectively. Panel B presents the grand average power spectra for the muscle components for both meditation and control states. In panel C, the thin, colored lines indicate difference in power across the range of frequencies for the muscle components; meditation minus control period for all subjects (when more than one component was present for a given subject, the power spectrum for these components was averaged). The bold, black trace indicates the grand average spectrum difference for the contrast meditation minus control such that segments above 0 indicate greater average component activity during meditation and below 0 indicate greater average component activity during control period

Fig. 4

Panel A indicates the grand average scalp map for vertical and horizontal eye-movement independent components, respectively. Panel B presents the grand average power spectra for the eye-movement components for both meditation and control states. In panel C, the thin, colored lines indicate the difference in power across the range of frequencies for the eye-movement components between meditation and control period for all subjects. The bold, black trace indicates the grand average spectrum difference for the contrast meditation minus control such that segments above 0 indicate greater average component activity during meditation and below 0 indicate greater average component activity during control period

Fig. 5

Panel A indicates the grand average scalp map for the occipital alpha independent components. Panel B presents the grand average power spectra of the occipital alpha components in meditation and control states. In panel C, the thin, colored lines indicate the difference in power across the range of frequencies for the occipital alpha components between meditation and control periods for all subjects. The bold, black trace indicates the grand average spectrum difference for the contrast meditation minus control. The gray bar at the bottom of the figure indicates frequencies over which bootstrap statistics with FDR correction for multiple comparisons indicated statistically significant greater values in meditation than control state (25–55 Hz)

Fig. 6

a Experimental order and alpha power. Participants undergoing the control period followed by the meditation period tended to evince greater alpha power during meditation, whereas those undergoing the meditation period followed by the control period tended to evince greater alpha power during the control period. b Meditators with less than 5 years of daily meditation practice (n = 6, M = 2.5, SD = 1.4) vs. meditators with 10 and greater years of daily meditation (n = 10, M = 19.3, SD = 8.5) practice showed different tendencies with regard to alpha power across experimental sessions, with shorter-term practitioners showing a trend toward greater alpha during meditation and longer-term practitioners showing the opposite pattern

Fig. 7

a Meditators with 10 and greater years of daily meditation practice in solid circles (n = 10, M = 19.3, SD = 8.5), Meditators with less than 5 years of daily meditation practice in solid circles (n = 6, M = 2.5, SD = 1.4), smaller “+” indicates the mean average occipital gamma in control vs. meditation conditions in shorter-term meditators, larger “+” indicates the mean average occipital gamma in control vs. meditation conditions in longer-term meditators. b Interaction between meditation expertise and occipital gamma effect