Alterations in the sense of time, space, and body in the mindfulness-trained brain: a neurophenomenologically-guided MEG study

Abstract

Meditation practice can lead to what have been referred to as "altered states of consciousness."One of the phenomenological characteristics of these states is a joint alteration in the sense of time, space, and body. Here, we set out to study the unique experiences of alteration in the sense of time and space by collaborating with a select group of 12 long-term mindfulness meditation (MM) practitioners in a neurophenomenological setup, utilizing first-person data to guide the neural analyses. We hypothesized that the underlying neural activity accompanying alterations in the sense of time and space would be related to alterations in bodily processing. The participants were asked to volitionally bring about distinct states of "Timelessness" (outside time) and "Spacelessness" (outside space) while their brain activity was recorded by MEG. In order to rule out the involvement of attention, memory, or imagination, we used control states of "Then" (past) and "There" (another place). MEG sensors evidencing alterations in power values were identified, and the brain regions underlying these changes were estimated via spatial filtering (beamforming). Particularly, we searched for similar neural activity hypothesized to underlie both the state of "Timelessness" and "Spacelessness." The results were mostly confined to the theta band, and showed that: (1) the "Then"/"There" overlap yielded activity in regions related to autobiographic memory and imagery (right posterior parietal lobule (PPL), right precentral/middle frontal gyrus (MFG), bilateral precuneus); (2) "Timelessness"/"Spacelessness" conditions overlapped in a different network, related to alterations in the sense of the body (posterior cingulate, right temporoparietal junction (TPJ), cerebellum); and (3) phenomenologically-guided neural analyses enabled us to dissociate different levels of alterations in the sense of the body. This study illustrates the utility of employing experienced contemplative practitioners within a neurophenomenological setup for scientifically characterizing a self-induced altered sense of time, space and body, as well as the importance of theta activity in relation with these altered states.

Keywords: body perception; magnetoencephalography (MEG); mindfulness meditation; neurophenomenolgy; space perception; theta rhythm; time perception.

Figure 1

Experimental protocol. The time and sequence of conditions in the two MEG sessions of “time” and “space.” Yellow—“There”/“Then,” blue—“Here”/“Now,” and purple—“Timelessness”/“Spacelessness” conditions. All epochs were initiated by an auditory cue (marked by arrows).

Figure 2

Rating of task success and stability. (A) Participants' rating (Mean ± s.e.m., n = 12) for success and stability during the different conditions. ^*p < 0.05, ^**p < 0.005, Bonferonni-corrected; (B) A scatterplot for the Timelessness vs. Spacelessness rated success. BTS, Both time and space; NTS, Not both Time and Space. Yellow dot refers to one OBE participant.

Figure 3

2D scalp maps of theta power SC contrasts. 2D topographic representations of significant sensor-level theta power (4–8 Hz) SC for the Timelessness vs. Now (Right), and Spacelessness vs. Here (Left). Crosses on the map represent significant clusters; color bar scale indicates t-values.

Figure 4

Beamforming source estimates for the overlap between Timelessness vs. Now and Spacelessness vs. Here contrasts in the theta (4–8 Hz) frequency. Axial, sagittal and coronal views (left to right) of group (n = 11) SAM pseudo-F source estimates overlayed on the Colin template. Note that in all images right and left sides are crossed. Green, orange, and red indicate Timelessness, Spacelessness and overlap between conditions, respectively. Top: left cingulate/precuneus and culmen (clusters 2 and 4, respectively, Table 3); Center: right cingulate/precuneus (cluster 1, Table 3); Bottom: right superior temporal gyrus (cluster 3, Table 3).

Figure 5

Beamforming source estimates for the overlap between Then vs. Now and There vs. Here contrasts in the theta (4–8 Hz) frequency. Axial, sagittal, and coronal views (left to right) of group (n = 11) SAM pseudo-F source estimates overlayed on the Colin template. Note that in all images right and left sides are crossed. Green, orange and red indicate Then, There and overlap between conditions, respectively. Top: left paracentral lobule and precuneus (cluster 3, Table 3). In the sagittal view, the same cluster (red) is compared with left cingulate/precuneus activity (cyan) for the Timelesness/Spacelessness overlap (cluster 2, Table 3). Note the clear separation between the superior cluster found in the Then/There overlap, and the inferior cluster found for the Timelesness/Spacelessness overlap; Center: right precentral and middle frontal gyrus (cluster 2, Table 3); Bottom: posterior parietal lobule (cluster 1, Table 3).

Figure 6

Differences in theta activity between the BTS (n = 5) and NTS (n = 6) groups over 4 overlapping ROIs. (A) Group × Cluster interaction. BTS, both time and space; NTS, Not both Time and Space; (B) Spacelessness (top) and Timelessness (bottom) group theta differences within the 4 clusters, calculated as BTS minus NTS. Color scale denotes log(theta power) values. Left column—right superior temporal gyrus (STG); Middle column—right posterior cingulated cortex (PCC); Right column—left PCC and cerebellum clusters.

Figure 7

Theta activity differences between the BTS (n = 4) and NTS (n = 5) groups over insula. (A) Group main effect. ^*p < 0.05. BTS, both time and space; NTS, Not both Time and Space. (B) Condition × Hemisphere interaction. R, right; L, left. (C) Group differences in theta activity, calculated as BTS minus NTS. Color scale denotes log(theta power) values.

Figure 8

OBE participant activity in the ROIs. Mean log theta power during the Timelessness and Spacelessness conditions, in the selected ROIs.