Abstract
Several cortical regions are reported to vary in meditation practitioners. However, prior analyses have focused primarily on examining gray matter or cortical thickness. Thus, additional effects with respect to other cortical features might have remained undetected. Gyrification (the pattern and degree of cortical folding) is an important cerebral characteristic related to the geometry of the brain’s surface. Thus, exploring cortical gyrification in long-term meditators may provide additional clues with respect to the underlying anatomical correlates of meditation. This study examined cortical gyrification in a large sample (n = 100) of meditators and controls, carefully matched for sex and age. Cortical gyrification was established by calculating mean curvature across thousands of vertices on individual cortical surface models. Pronounced group differences indicating larger gyrification in meditators were evident within the left precentral gyrus, right fusiform gyrus, right cuneus, as well as left and right anterior dorsal insula (the latter representing the global significance maximum). Positive correlations between gyrification and the number of meditation years were similarly pronounced in the right anterior dorsal insula. Although the exact functional implications of larger cortical gyrification remain to be established, these findings suggest the insula to be a key structure involved in aspects of meditation. For example, variations in insular complexity could affect the regulation of well-known distractions in the process of meditation, such as daydreaming, mind-wandering, and projections into past or future. Moreover, given that meditators are masters in introspection, awareness, and emotional control, increased insular gyrification may reflect an integration of autonomic, affective, and cognitive processes. Due to the cross-sectional nature of this study, further research is necessary to determine the relative contribution of nature and nurture to links between cortical gyrification and meditation.
Highlights
The global significance maximum was located within the right anterior dorsal insula indicating a larger gyrification in meditators compared to controls
A recent functional imaging experiment revealed shorter neural responses in regions of the default-mode network (DMN) in meditators compared to controls suggesting that “the regular practice of Zen meditation enhances the capacity for voluntary regulation of spontaneous mental activity” (Pagnoni et al, 2008)
The group differences between meditators and controls as well as the links between local gyrification and number of meditation years point to cortical regions involved in processes related to meditation, with particular involvement of the anterior dorsal insula
Summary
Various brain regions have been reported to be anatomically different between meditators and controls, to show associations with the amount of meditation practice, and/or to change as a consequence of meditation exercises (Lazar et al, 2005; Pagnoni and Cekic, 2007; Holzel et al, 2008, 2010; Vestergaard-Poulsen et al, 2008; Luders et al, 2009, 2011a,b; Grant et al, 2010; Tang et al, 2010) Many of these aforementioned effects were evident across the lateral and medial surfaces of the cortex as well as buried beneath it (e.g., within the insula) suggesting the cerebral cortex to be heavily involved in processes related to meditation. Meditation practitioners who are seriously committed to a long-term practice provide an ideal human model for investigating brain plasticity given their ongoing, frequent, and regular mental efforts
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