Gray Matter and Functional Connectivity in Anterior Cingulate Cortex are Associated with the State of Mental Silence During Sahaja Yoga Meditation

Abstract—Some meditation techniques teach the practitioner to achieve the state of mental silence. The aim ofthis study was to investigate brain regions that are associated with their volume and functional connectivity(FC) with the depth of mental silence in long-term practitioners of Sahaja Yoga Meditation. Twenty-three long-term practitioners of this meditation were scanned using Magnetic Resonance Imaging. In order to identify theneural correlates of the depth of mental silence, we tested which gray matter volumes (GMV) were correlated withthe depth of mental silence and which regions these areas were functionally connected to under a meditation con-dition. GMV in medial prefrontal cortex including rostral anterior cingulate cortex were positively correlated withthe subjective perception of the depth of mental silence inside the scanner. Furthermore, there was significantlyincreased FC between this area and bilateral anterior insula/putamen during a meditation-state specifically, whiledecreased connectivity with the right thalamus/parahippocampal gyrus was present during the meditation-stateand the resting-state. The capacity of long-term meditators to establish a durable state of mental silence insidean MRI scanner was associated with larger gray matter volume in a medial frontal region that is crucial for top-down cognitive, emotion and attention control. This is furthermore corroborated by increased FC of this regionduring the meditation-state with bilateral anterior insula/putamen, which are important for interoception, emotion,and attention regulation. The findings hence suggest that the depth of mental silence is associated with medialfronto-insular-striatal networks that are crucial for top-down attention and emotional control

Resting state functional connectivity associated with sahaja yoga meditation

Neuroscience research has shown that meditation practices have effects on brain structure and function. However, few studies have combined information on the effects on structure and function in the same sample. Long-term daily meditation practice produces repeated activity of specific brain networks over years of practice, which may induce lasting structural and functional connectivity (FC) changes within relevant circuits. The aim of our study was therefore to identify differences in FC during the resting state between 23 Sahaja Yoga Meditation experts and 23 healthy participants without meditation experience. Seed-based FC analysis was performed departing from voxels that had shown structural differences between these same participants. The contrast of connectivity maps yielded that meditators showed increased FC between the left ventrolateral prefrontal cortex and the right dorsolateral prefrontal cortex but reduced FC between the left insula and the bilateral mid-cingulate as well as between the right angular gyrus and the bilateral precuneus/cuneus cortices. It thus appears that long-term meditation practice increases direct FC between ventral and dorsal frontal regions within brain networks related to attention and cognitive control and decreases FC between regions of these networks and areas of the default mode network

Reduced striatal volume in cocaine-dependent patients.

Long-term cocaine consumption is associated with brain structural and functional changes. While the animal literature on cocaine use and dependence has traditionally focused on the striatum, previous human studies using voxel-based morphometry have reported reduced volumes of gray matter in several brain areas, but not in the striatum. Brain magnetic resonance imaging was performed with 20 cocaine-dependent patients and 16 healthy age-, education- and intelligence-matched control men. The cocaine-dependent group had lower gray matter volumes in the striatum and right supramarginal gyrus compared to controls. Within the cocaine-dependent group, years of cocaine use were inversely associated with the volume of the bilateral middle frontal gyrus, left superior frontal gyrus, parahippocampus, posterior cingulate, amygdala, insula, right middle temporal gyrus and cerebellum. These results show that cocaine dependence is associated with reduced gray matter volumes in the target structures of the dopaminergic system. These findings are the first to suggest reduced gray matter in the striatum by means of voxel-based morphometry in human users, thereby linking human results to animal models of addiction. In addition, the relationship between years of use and grey matter volumes in numerous brain regions are consistent with these volume reductions arising as a consequence of the cocaine use