Abstract
Previous cross-sectional studies reported positive effects of meditation on the brain areas related to attention and executive function in the healthy elderly population. Effects of long-term regular meditation in persons with mild cognitive impairment (MCI) and Alzheimer’s disease dementia (AD) have rarely been studied. In this study, we explored changes in cortical thickness and gray matter volume in meditation-naïve persons with MCI or mild AD after long-term meditation intervention. MCI or mild AD patients underwent detailed clinical and neuropsychological assessment and were assigned into meditation or non-meditation groups. High resolution T1-weighted magnetic resonance images (MRI) were acquired at baseline and after 6 months. Longitudinal symmetrized percentage changes (SPC) in cortical thickness and gray matter volume were estimated. Left caudal middle frontal, left rostral middle frontal, left superior parietal, right lateral orbitofrontal, and right superior frontal cortices showed changes in both cortical thickness and gray matter volume; the left paracentral cortex showed changes in cortical thickness; the left lateral occipital, left superior frontal, left banks of the superior temporal sulcus (bankssts), and left medial orbitofrontal cortices showed changes in gray matter volume. All these areas exhibited significantly higher SPC values in meditators as compared to non-meditators. Conversely, the left lateral occipital, and right posterior cingulate cortices showed significantly lower SPC values for cortical thickness in the meditators. In hippocampal subfields analysis, we observed significantly higher SPC in gray matter volume of the left CA1, molecular layer HP, and CA3 with a trend for increased gray matter volume in most other areas. No significant changes were found for the hippocampal subfields in the right hemisphere. Analysis of the subcortical structures revealed significantly increased volume in the right thalamus in the meditation group. The results of the study point out that long-term meditation practice in persons with MCI or mild AD leads to salutary changes in cortical thickness and gray matter volumes. Most of these changes were observed in the brain areas related to executive control and memory that are prominently at risk in neurodegenerative diseases.
Highlights
Alzheimer’s disease is a clinico-pathological continuum caused by abnormal deposition of misfolded beta-amyloid and tau proteins with progressive breakdown along the core neurocognitive networks in the brain
We try to address some of these issues as we investigate the impact of long-term daily silent, sitting meditation on brain gray matter volume and cortical thickness in MCI and mild AD patients
In within-group analysis between two-time points, we found a widespread increase in cortical thickness or gray matter volume in the meditation group, prominently over the left prefrontal cortex, and on the right
Summary
Alzheimer’s disease is a clinico-pathological continuum caused by abnormal deposition of misfolded beta-amyloid and tau proteins with progressive breakdown along the core neurocognitive networks in the brain. Around 10–15% of patients with MCI could convert to Alzheimer’s disease dementia (hitherto referred as “AD”), Petersen et al (2001) and over half of all converters are likely to do so within 5 years (Gauthier et al, 2006). The default component is passive mind wandering, from where the meditator has to repeatedly turn the attention back to the task at hand. Other techniques such as loving-kindness meditation and meditation on peace, where faces, thoughts, or scenes are visualized, respectively, could be considered variants of “focused attention” meditation
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