Reduces self-related thinking and mind-wandering

Garrison, K. A., et al. (2015). Meditation leads to reduced default mode network activity beyond an active task. Cognitive, Affective, & Behavioral Neuroscience, 1-9.

From the Abstract. Meditation has been associated with relatively reduced activity in the default mode network, a brain network implicated in self-related thinking and mind wandering. However, previous imaging studies have typically compared meditation to rest, despite other studies having reported differences in brain activation patterns between meditators and controls at rest. Moreover, rest is associated with a range of brain activation patterns across individuals that has only recently begun to be better characterized.

Therefore, in this study we compared meditation to another active cognitive task, both to replicate the findings that meditation is associated with relatively reduced default mode network activity and to extend these findings by testing whether default mode activity was reduced during meditation, beyond the typical reductions observed during effortful tasks.

In addition, prior studies had used small groups, whereas in the present study we tested these hypotheses in a larger group. The results indicated that meditation is associated with reduced activations in the default mode network, relative to an active task, for meditators as compared to controls. These findings … suggest that meditation leads to relatively reduced default mode processing beyond that observed during another active cognitive task.

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Neural mechanisms remain unclear (review)

Tang, Y. Y., Hölzel, B. K., & Posner, M. I. (2015). The neuroscience of mindfulness meditation. Nature Reviews Neuroscience, 16, 213–225. doi:10.1038/nrn3916. Abstract (including 180 references). Full text at lead author’s website.

Research over the past two decades broadly supports the claim that mindfulness meditation — practiced widely for the reduction of stress and promotion of health — exerts beneficial effects on physical and mental health, and cognitive performance. Recent neuroimaging studies have begun to uncover the brain areas and networks that mediate these positive effects.

However, the underlying neural mechanisms remain unclear, and it is apparent that more methodologically rigorous studies are required if we are to gain a full understanding of the neuronal and molecular bases of the changes in the brain that accompany mindfulness meditation.

Sex-divergent findings re hippocampal dimensions

Luders, E., Thompson, P. M., & Kurth, F. (2015). Larger Hippocampal Dimensions in Meditation Practitioners: Differential Effects in Women and Men. Frontiers in Psychology, 6, 186. To access full text, go to Abstract and retrieve provisional PDF.

hippopotamus-baby-beautiful-164-1On average, the human hippocampus shows structural differences between meditators and non-meditators as well as between men and women. However, there is a lack of research exploring possible sex effects on hippocampal anatomy in the framework of meditation.

Thus, we obtained high-resolution magnetic resonance imaging data from 30 long-term meditation practitioners (15 men / 15 women) and 30 well-matched control subjects (15 men / 15 women) to assess if hippocampus-specific effects manifest differently in male and female brains.

Hippocampal dimensions were enlarged both in male and in female meditators when compared to sex- and age-matched controls. However, meditation effects differed between men and women in magnitude, laterality, and location on the hippocampal surface. Such sex-divergent findings may be due to genetic (innate) or acquired differences between male and female brains in the areas involved in meditation and/or suggest that male and female hippocampi are differently receptive to mindfulness practices.

How does loving-kindness meditation alter brain and body?

Mascaro, J. S., Darcher, A., Negi, L. T., & Raison, C. (2015). The neural mediators of kindness-based meditation: a theoretical model. Frontiers in Psychology, 6, 109. To access full text, click here, then open PDF.

brain-budAbstract. Although kindness-based contemplative practices are increasingly employed by clinicians and cognitive researchers to enhance prosocial emotions, social cognitive skills, and well-being, and as a tool to understand the basic workings of the social mind, we lack a coherent theoretical model with which to test the mechanisms by which kindness-based meditation may alter the brain and body.

Here we link contemplative accounts of compassion and lovingkindness practices with research from social cognitive neuroscience and social psychology to generate predictions about how diverse practices may alter brain structure and function and related aspects of social cognition.

Contingent on the nuances of the practice, kindness-based meditation may enhance the neural systems related to faster and more basic perceptual or motor simulation processes, simulation of another’s affective body state, slower and higher-level perspective-taking, modulatory processes such as emotion regulation and self/other discrimination, and combinations thereof.

This theoretical model will be discussed alongside bestpractices for testing such a model and potential implications and applications of future work.

EEG measures manifestations of nondual awareness

Berman, A. E., & Stevens, L. (2015). EEG manifestations of nondual experiences in meditators. Consciousness and Cognition, 31, 1-11. Abstract

Highlights • Nondual states of consciousness reflect the culminating meditation experience. • These resulting states are differentiated from method or type of practice. • EEGs were recorded during meditation and states of nonduality. • Results suggest nondual states are neurologically distinct from general meditation. • Differentiating method and state will contribute to a more comprehensive taxonomy.

The holistic experiential benefits of meditation among a widely ranging population have been well established within the empirical literature. What remain less clear are the underlying mechanisms of the meditative process. A large impediment to this clarity is attributable to the lack of a unified and comprehensive taxonomy, as well as to the absence of clear differentiation within the literature between method of practice and resulting state.

The present study discusses and then attempts to identify within our sample a theoretically universal culminating meditative state known as Nondual Awareness, which is differentiated from the method or practice state. Participants completed an in-lab meditation, during which neurological patterns were analyzed using electroencephalography (EEG).

Analyses indicated significantly higher EEG power among slower wave frequencies (delta, theta, alpha) during the reported nondual events. These events appear neurologically distinct from meditation sessions as a whole, which interestingly demonstrated significant elevation within the gamma range.

Mindfulness in the brain

Fletcher, L. B., Schoendorff, B., & Hayes, S. C. (2010). Searching for mindfulness in the brain: A process-oriented approach to examining the neural correlates of mindfulness. Mindfulness, 1(1), 41-63. Full text.

Abstract. There has been great interest of late in trying to capture the benefits of meditation by scanning meditators’ brains. In this paper, we argue that a successful neuroscience of mindfulness needs to be based on an adequate psychological analysis.

We present a definition of mindfulness based on four psychological processes that are relatively well understood, and we show how this model may help organize neuroimaging research and create a bridge to clinical applications.

This framework provides an approach to neuroscience research grounded in psychological principles and theory. We propose that this is critical for advancing scientific endeavors such that the knowledge gained helps improve the human condition.

Interventions in mild cognitive impairment and Alzheimer’s disease

Larouche, E., Hudon, C., & Goulet, S. (2014). Potential benefits of mindfulness-based interventions in mild cognitive impairment and Alzheimer’s disease: An interdisciplinary perspective. Behavioural Brain Research. In Press. Abstract.

Highlights: • Hippocampal damage is central in MCI/AD and could be prevented or delayed by mindfulness-based interventions (MBI).  • MBI reduce MCI/AD adverse factors (stress, depression, metabolic syndrome).  • Multiple pathways could explain MBI’s effects on modifiable adverse factors.  • Effects seem based on neuro- endocrine, immune, and transmission regulation.  • MBI show great potential to prevent the neurodegenerative cascade leading to AD.

The present article is based on the premise that the risk of developing Alzheimer’s disease (AD) from its prodromal phase (mild cognitive impairment; MCI) is higher when adverse factors (e.g., stress, depression, and metabolic syndrome) are present and accumulate. Such factors augment the likelihood of hippocampal damage central in MCI/AD aetiology, as well as compensatory mechanisms failure triggering a switch toward neurodegeneration. Because of the devastating consequences of AD, there is a need for early interventions that can delay, perhaps prevent, the transition from MCI to AD.

We hypothesize that mindfulness-based interventions (MBI) show promise with regard to this goal. The present review discusses the associations between modifiable adverse factors and MCI/AD decline, MBI’s impacts on adverse factors, and the mechanisms that could underlie the benefits of MBI. A schematic model is proposed to illustrate the course of C specific to MCI/AD, as well as the possible preventive mechanisms of MBI. Whereas regulation of glucocorticosteroids, inflammation, and serotonin could mediate MBI’s effects on stress and depression, resolution of the metabolic syndrome might happen through a reduction of inflammation and white matter hyperintensities, and normalization of insulin and oxidation.

The literature reviewed in this paper suggests that the main reach of MBI over MCI/AD development involves the management of stress, depressive symptoms, and inflammation. Future research must focus on achieving deeper understanding of MBI’s mechanisms of action in the context of MCI and AD. This necessitates bridging the gap between neuroscientific subfields and a cross-domain integration between basic and clinical knowledge.