Commentary: Meditation Effects within the Hippocampal Complex Revealed by Voxel-Based Morphometric and Cytoarchitectonic Probabilistic Mapping

Citation: Mukerji Househam A and Josipovic Z (2015) Commentary: Meditation Effects within the Hippocampal Complex Revealed by Voxel-Based Morphometric and Cytoarchitectonic Probabilistic Mapping. The discovery of experience-dependent structural plasticity in the adult human brain is, arguably, one of the most significant recent developments in neuroscience (Maguire et al., 2000; Gage, 2002). The evidence of structural changes related to cognitive and motor practices, and skill acquisition, has inspired considerable clinical research into their potential relevance for diagnostic and therapeutic methods (Prosperini et al., 2015). Meditation and mindfulness include a wide variety of cognitive and affective practices, usually done long-term, with a broad impact that ranges from stress reduction and immune response enhancement, to optimizing cognitive functioning and affect regulation (Lutz et al., 2007). Since the first morphometric study of the effects of meditation by Lazar et al. (2005), a number of findings have been made showing increases in the volume and density of gray matter, and in the axonal connectivity of white matter (for review see Fox et al., 2014). An interesting finding has been that such changes could occur not only after many years of meditation practice, but also after a short 8-week training (Hölzel et al., 2011). Increases in volume or density of gray matter have been found in a number of areas involved in mediating meditation experience, such as the frontal pole, orbito-frontal cortex, anterior cingulate, insula, sensory cortices, and the hippocampal complex (Lazar et al. An ongoing issue for morphometric studies using MRI and PET has been disentangling what exactly is contributing to the observed increases in cortical thickness. As pointed out early on Lazar et al. (2005), an increase in the gray matter thickness could mean an increase in the number of neurons, but also an increase in dendritic arborization, glial cells, cerebral vasculature, or a combination of these factors.