Decoding meditation mechanisms underlying brain preservation and psycho-affective health in older expert meditators and older meditation-naive participants

Abstract

Meditation is a mental training approach that can improve mental health and well-being in aging. Yet the underlying mechanisms remain unknown. The Medit-Ageing model stipulates that three mechanisms - attentional, constructive, and deconstructive - upregulate positive psycho-affective factors and downregulate negative ones. To test this hypothesis, we measured brain structural MRI and perfusion, negative and positive psycho-affective composite scores, and meditation mechanisms in 27 older expert meditators and 135 meditation-naive older controls. We identified brain and psycho-affective differences and performed mediation analyses to assess whether and which meditation mechanisms mediate their links.Meditators showed significantly higher volume in fronto-parietal areas and perfusion in temporo-occipito-parietal areas. They also had higher positive and lower negative psycho-affective scores. Attentional and constructive mechanisms both mediated the links between brain differences and the positive psycho-affective score whereas the deconstructive mechanism mediated the links between brain differences and the negative psycho-affective score.Our results corroborate the Medit-Ageing model, indicating that, in aging, meditation leads to brain changes that decrease negative psycho-affective factors and increase positive ones through relatively specific mechanisms. Shedding light on the neurobiological and psycho-affective mechanisms of meditation in aging, these findings provide insights to refine future interventions.

Fig. 1

Voxel-wise differences between older expert meditators and older meditation-naive controls. The results are projected on medial and external 3D brain surface views of the MNI template. The clusters indicate areas where older expert meditators showed significantly greater (a) GMV, gray matter volume, and (b) perfusion than controls. Dark blue = bilateral inferior frontal gyrus (1), Green = left orbitofrontal cortex (2), Purple = bilateral posterior cingulate cortex (3), Pink = left temporal cluster (4), Light blue = left temporo-occipital cluster (5), Orange = right temporo-occipito-parietal cluster (6), Yellow = left temporo-parietal cluster (7). Results were evaluated for significance at p_uncorrected<0.005 combined with a minimum cluster size determined by Monte-Carlo simulations using the AFNI’s 3dClustSim program to achieve a corrected statistical significance of p < 0.05.

Fig. 2

Group differences for psycho-affective scores and meditation mechanisms. Boxplots illustrating the differences between the meditators (purple) and controls (orange) for the positive psycho-affective score (a) negative psycho-affective score (b), Attentional mechanism (c) Constructive mechanism (d) and Deconstructive mechanism (e). ***: All differences were significant with p < 0.0001.

Fig. 3

Diagram of the mediation models illustrating the predictor (gray matter volume, perfusion), potential mediators (attentional, constructive and deconstructive mechanisms) and outcomes (positive and negative psycho-affective scores). Direct effects in filled arrows (simple regressions between variables) are expressed as standardized regression coefficients and indirect effects in dotted arrows (multiple regressions in which the predictor and the mediator are both added in the model) as partial correlation coefficients. Significant models are highlighted in bold black while the non-significant one is in gray. All regressions are adjusted for age, sex, and education. *p < 0.05, **p < 0.01, ***p < 0.001.

Fig. 4

Design overview. a. 27 older expert meditators and 135 older healthy meditation-naive controls underwent neuroimaging acquisitions for different modalities and filled self-reported measures that were used to construct composite scores reflecting psycho-affective scores and meditation mechanisms. b. (1) Whole brain voxel-wise comparisons were performed to assess the structural and functional brain regions better preserved in expert meditators compared to controls. Volume and perfusion values were then extracted from the regions highlighted for further analyses. Then, both populations were compared on their measures of psycho-affective scores and meditation mechanisms using ANCOVAs (aov package – R studio). (2) Multiple linear regressions were performed between each psycho-affective score (dependant variable) and each meditation mechanism (independent variable) to assess, for each meditation mechanism, whether it predominantly influenced one psycho-affective score over the other. c. Mediation analyses were performed based on the results of 2), and the selection of the brain regions that best predicted each mechanism, to assess whether the meditation mechanisms mediated the relationship between brain regions and psycho-affective scores. Abbreviations: MRI Magnetic Resonance Imaging, PET Positron Emission Tomography; ANCOVA ANalysis of COVAriance.