sLORETA intracortical lagged coherence during breath counting in meditation-naïve participants

Abstract

We investigated brain functional connectivity comparing no-task resting to breath counting (a meditation exercise but given as task without referring to meditation). Functional connectivity computed as EEG coherence between head-surface data suffers from localization ambiguity, reference dependence, and overestimation due to volume conduction. Lagged coherence between intracortical model sources addresses these criticisms. With this analysis approach, experienced meditators reportedly showed reduced coherence during meditation, meditation-naïve participants have not yet been investigated. 58-channel EEG from 23 healthy, right-handed, meditation-naïve males during resting [3 runs] and breath counting [2 runs] was computed into sLORETA time series of intracortical electrical activity in 19 regions of interest (ROI) corresponding to the cortex underlying 19 scalp electrode sites, for each of the eight independent EEG frequency bands covering 1.5-44 Hz. Intracortical lagged coherences and head-surface conventional coherences were computed between the 19 regions/sites. During breath counting compared to resting, paired t-tests corrected for multiple testing revealed four significantly lower intracortical lagged coherences, but four significantly higher head-surface conventional coherences. Lowered intracortical lagged coherences involved left BA 10 and right BAs 3, 10, 17, 40. In conclusion, intracortical lagged coherence can yield results that are inverted to those of head-surface conventional coherence. The lowered functional connectivity between cognitive control areas and sensory perception areas during meditation-type breath counting compared to resting conceivably reflects the attention to a bodily percept without cognitive reasoning. The reductions in functional connectivity were similar but not as widespread as the reductions reported during meditation in experienced meditators.

Keywords: EEG; breath counting; functional connectivity; intracortical coherence; lagged coherence; meditation; sLORETA.

Figure 1

(A) sLORETA-based intracortical lagged coherences that differed during breath counting compared to resting at p(corrected) < 0.05. All four connectivities were lower during breath counting. (B) Head-surface conventional coherences that differed during breath counting compared to resting at p(corrected) < 0.05. All four connectivities were higher during breath counting. Glass brain axial, sagittal, and coronal views, left ear left; ROI locations are indicated by dots. For ease of visualization, the intracortical ROIs are represented by the corresponding head-surface locations of the standard 19 electrode positions of the international 10–20 system.