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. 2019 Feb 22;10:210.
doi: 10.3389/fpsyg.2019.00210. eCollection 2019.

Spontaneous Visual Imagery During Meditation for Creating Visual Art: An EEG and Brain Stimulation Case Study

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Free PMC article

Spontaneous Visual Imagery During Meditation for Creating Visual Art: An EEG and Brain Stimulation Case Study

Caroline Di Bernardi Luft et al. Front Psychol. .
Free PMC article

Abstract

Experienced meditators often report spontaneous visual imagery during deep meditation in the form of lights or other types of visual images. These experiences are usually interpreted as an "encounters with light" and gain mystical meaning. Contrary to the well-studied intentional and controlled visual imagery, spontaneous imagery is poorly understood, yet it plays an important role in creativity of visual artists. The neural correlates of such experiences are indeed hard to capture in laboratory settings. In this case study we aimed to investigate the neural correlates of spontaneous visual imagery in an artist who experiences strong visual imagery during meditation. She uses these images to create visual art. We recorded her EEG during seven meditation sessions in which she experienced visual imagery episodes (visions). To examine the functional role of the neural oscillations we also conducted three separate meditation sessions under different transcranial alternating current (tACS) brain stimulation: alpha (10 Hz), gamma (40 Hz) and sham. We observed a robust increase in occipital gamma power (30-70 Hz) during the deepest stage of meditation across all sessions. This gamma increase was consistent with the experience of spontaneous visual imagery: higher during visions compared to no visions. Alpha tACS was found to affect the contents of her visual imagery, making them sharper, shorter and causing more visions to occur; the artist reported that these sharp images were too detailed to be used in her art. Interestingly, gamma and sham stimulation had no impact on the visual imagery contents. Our findings raise the hypothesis that occipital gamma might be a neural marker of spontaneous visual imagery, which emerges in certain meditation practices of experienced meditators.

Keywords: EEG; alpha oscillations; entrainment; gamma oscillations; meditation; spontaneous visual imagery; transcranial alternating current stimulation (tACS); visual arts.

Figures

FIGURE 1
FIGURE 1
Overview of the meditation sessions. (A) The sessions in which the EEG was recorded are represented in blue whereas the meditation sessions that occurred under tACS are in red. A practice day is represented in yellow. In these practice sessions, the participant practiced the meditation indicating the onset and offset of the visions with a button press (once she was on stage 3). The duration of each session is presented next to each box. In the brain stimulation session, the duration of the stimulation is described as Stim ON whereas the total duration of the meditation in “Med.”. It is important to notice that in the tACS sessions the meditation occurred simultaneously with brain stimulation. In those cases, the tACS stopped after 30 min while the meditation stopped shortly after (B) Example of the art produced by Lia Chavez during her meditation process. Each individual element of the part represents a vision, which are drawn during her meditation, with eyes closed. Carceri 11, 2014. Acrylic paint, charcoal, graphite, oil pastel, and ink on Japanese paper. 72 × 113 inches (182.88 × 287.02 cm) Lia Chavez.
FIGURE 2
FIGURE 2
EEG oscillations during the first meditation session. Gamma power changes from baseline during each stage or deepness of meditation (Stages 1, 2, 3) as indicated by the artist in the first session (sessions 1A and 1B). We analyzed the relative power over the traditional frequency bands: theta (4–8 Hz), alpha (8–12 Hz), beta (13–30 Hz), gamma 1 (30–45 Hz), and gamma 2 (55–80 Hz) as the percent signal change from stage 0.
FIGURE 3
FIGURE 3
EEG oscillations during the second meditation session. The figure display the gamma power changes from baseline during each stage or deepness of meditation (Stages 1, 2, 3) as indicated by the artist in the second session (sessions 2A and 2B). We analyzed the relative power over the traditional frequency bands: theta (4–8 Hz), alpha (8–12 Hz), beta (13–30 Hz), gamma 1 (30–45 Hz), and gamma 2 (55–80 Hz) as the percent signal change from stage 0.
FIGURE 4
FIGURE 4
Gamma oscillations during each stage of meditation in four sessions. (A) Occipital (O2, Oz, and O1) gamma power (30–80 Hz) during stages 1, 2, and 3 of meditation in the two main sessions (days 1 and 2) and the corresponding meditation sessions (A and B as first and second meditation round). The topography of gamma power in relation to baseline for each session is presented above each error bar. The topographical maps highlighted with a thick gray line correspond to stage 3 of meditation. (B) Frontal (AF4, AFz, and AF3) gamma power (30–80 Hz) during stages 1, 2, and 3 of meditation in the two main sessions (days 1 and 2) and the corresponding meditation sessions (A and B as first and second meditation round). The error bars represent +/–1 S.E.M. The asterisks represent the pairwise comparisons (Bonferroni Corrected) between the conditions: p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001.
FIGURE 5
FIGURE 5
Duration of visual imagery events during and after tACS brain stimulation and sham. Mean vision duration (s) during (A) and after (B) tACS in gamma and alpha frequency and sham.
FIGURE 6
FIGURE 6
Gamma oscillations during spontaneous visual imagery. (A) Right occipital gamma (35–80 Hz) power (P8, P10, PO4, PO8, O2) during visions (red) vs. no visions (blue) during meditation stage 3 following gamma, alpha, and sham tACS conditions. (B) Frontal gamma (35–80 Hz) power (F3,F4,T7,T8,C5,C6) during visions (red) vs. no visions (blue) during meditation stage 3 following gamma, alpha, and sham tACS conditions. Error bars represent +/–1 S.E.M across epochs (vision and no vision epochs of 2 s each). ∗∗∗p < 0.001.
FIGURE 7
FIGURE 7
Gamma oscillations during each stage of meditation following gamma and alpha stimulation sessions. Occipital (O2, Oz, and O1) gamma power (30–80 Hz) during stages 1, 2, and 3 of meditation (from brighter to darker red) following gamma and alpha tACS sessions. The power values are relative to baseline (stage 0). The error bars represent +/–1 S.E.M. The asterisks represent the pairwise comparisons (Bonferroni Corrected) between the conditions: p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001.

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