Evolution from four mental states to the highest state of consciousness: A neurophysiological basis of meditation as defined in yoga texts

Beyond the veil of duality-topographic reorganization model of meditation

Meditation can exert a profound impact on our mental life, with proficient practitioners often reporting an experience free of boundaries between a separate self and the environment, suggesting an explicit experience of "nondual awareness." What are the neural correlates of such experiences and how do they relate to the idea of nondual awareness itself? In order to unravel the effects that meditation has on the brain's spatial topography, we review functional magnetic resonance imaging brain findings from studies specific to an array of meditation types and meditator experience levels. We also review findings from studies that directly probe the interaction between meditation and the experience of the self. The main results are (i) decreased posterior default mode network (DMN) activity, (ii) increased central executive network (CEN) activity, (iii) decreased connectivity within posterior DMN as well as between posterior and anterior DMN, (iv) increased connectivity within the anterior DMN and CEN, and (v) significantly impacted connectivity between the DMN and CEN (likely a nonlinear phenomenon). Together, these suggest a profound organizational shift of the brain's spatial topography in advanced meditators-we therefore propose a topographic reorganization model of meditation (TRoM). One core component of the TRoM is that the topographic reorganization of DMN and CEN is related to a decrease in the mental-self-processing along with a synchronization with the more nondual layers of self-processing, notably interoceptive and exteroceptive-self-processing. This reorganization of the functionality of both brain and self-processing can result in the explicit experience of nondual awareness. In conclusion, this review provides insight into the profound neural effects of advanced meditation and proposes a result-driven unifying model (TRoM) aimed at identifying the inextricably tied objective (neural) and subjective (experiential) effects of meditation.

Neuroscience of the yogic theory of consciousness

Yoga as a practice and philosophy of life has been followed for more than 4500 years with known evidence of yogic practices in the Indus Valley Civilization. The last few decades have seen a resurgence in the utility of yoga and meditation as a practice with growing scientific evidence behind it. Significant scientific literature has been published, illustrating the benefits of yogic practices including 'asana', 'pranayama' and 'dhyana' on mental and physical well-being. Electrophysiological and recent functional magnetic resonance imaging (fMRI) studies have found explicit neural signatures for yogic practices. In this article, we present a review of the philosophy of yoga, based on the dualistic 'Sankhya' school, as applied to consciousness summarized by Patanjali in his yoga sutras followed by a discussion on the five 'vritti' (modulations of mind), the practice of 'pratyahara', 'dharana', 'dhyana', different states of 'samadhi', and 'samapatti'. We formulate the yogic theory of consciousness (YTC), a cohesive theory that can model both external modulations and internal states of the mind. We propose that attention, sleep and mind wandering should be understood as unique modulatory states of the mind. YTC allows us to model the external states, internal states of meditation, 'samadhi' and even the disorders of consciousness. Furthermore, we list some testable neuroscientific hypotheses that could be answered using YTC and analyse the benefits, outcomes and possible limitations.

Understanding Meditation Based on the Subjective Experience and Traditional Goal: Implications for Current Meditation Research

Owing to its benefits on various cognitive aspects, one's emotions, and well-being, meditation has drawn interest from several researchers and common public alike. We have different meditation practices associated with many cultures and traditions across the globe. Current literature suggests significant changes in the neural activity among the different practices of meditation, as each of these practices contributes to distinct physiological and psychological effects. Although this is the case, we want to find out if there is an underlying commonality among all these different practices. Thus, we ask the following questions related to different practices of meditation, the traditional goal of meditation and its significance-what is the central purpose of meditation? Do traditions define the final goal of all the practices of meditation? Are the purpose and goal of these practices different or is there a common goal to be attained through all these distinct practices? Embracing the traditional perspective, through this paper, we want to emphasize that, although these techniques and practices may appear different on the periphery, eventually, they seem to subject one to the same experience at the end, a natural meditative state (discussed in various spiritual traditions as the goal of meditation). In view of future studies on different meditation practices and also those exploring this subjective state, we offer some interesting ideas based on the traditional insights into meditation. In this context, we would also like to make a few comments on the way contemporary researchers view different practices of meditation.