The default mode network has a crucial but poorly understood role in how meditation influences brain structure and function. This paper sets out some of the current thinking regarding self-generated thought.
Authors: Andrews‐Hanna, J. R., Smallwood, J., & Spreng, R. N.
Title: The default network and self‐generated thought: component processes, dynamic control, and clinical relevance
Summary: It is frequently suggested that neuroscience is still in its infancy, this becomes patently clear when you start to consider how little we know about the default mode network (DMN). The DMN, also known as the default network (DN) or the task-negative network (TNN) is most active when humans are in a resting state. In short, the DMN is the network that takes over when we are not actively engaged in a specific task. Surprisingly it was assumed that the brain was resting when not engaged in an externally focussed activity. This assumption was surprising because scientists know that their brains are capable of complex processes such as mind wandering when they are not reacting to the external environment. However, only when it was demonstrated that functional brain activity could reach similar levels in task and non-task modes did the investigation into the DMN begin in earnest. This has particular relevance for meditators and contemplative science, as the DMN is often the direct and indirect target for meditation methods.
Andrews‐Hanna, Smallwood and Spreng produced a review of the leading findings linked to the DMN, which they describe as an anatomically diffuse global network. Their primary focus is the DMN and self-generated thought, thought that arise without external sensory stimulus. Describing much of the recent research in the field they conclude that the DMN plays an integrated role in a wide range of neurological functions. Thus both normal and abnormal mental health is dependent on activity and functional connectivity within the DMN and links to other neural networks. The paper provides a useful background to contemplative scientists looking for an understanding of how meditation might influence human behaviour.
Meditation and mindfulness may help to keep your brain young
Authors: Fotuhi, M., Lubinski, B., Trullinger, M., Hausterman, N., Riloff, T., Hadadi, M., & Raji, C. A.
Title: A personalized 12‐week ” Brain Fitness Program” for improving cognitive function and increasing the volume of hippocampus in elderly with mild cognitive impairment.
Summary: The idea that brain function inevitably declines as people grow older is firmly established in both clinical and cognitive branches of psychology. This particular study is one of only a handful that I have seen to suggest, that even in retirement, people can maintain and even increase both structure and function in the brain. Participants of retirement age with a diagnosis of mild cognitive impairment (MCI) were asked to engage in a number of activities linked to brain health. They included: cognitive stimulation, Omega 3 supplements, some physical exercise, a change in diet and mindfulness meditation. Participant undertook a range of cognitive tests before the interventions and at the end of the experiment.
Results showed that 84% of participants saw an improvement in their cognitive performance. Further neuroimaging examinations revealed that a majority of a sample of the participants also demonstrated no decline or an actual increase in the volume of the hippocampus. Although this was a preliminary study with a number of methodological problems, it is suggestive that people may have a lot more control over brain structure and function than is generally assumed. This kind of ‘shotgun’ approach can support general theories but adds little to our understanding of the extent to which particular interventions (or combination of interventions) may offer benefit. It also makes the establishment of robust scientific theory a challenge, as no single theory can incorporate such a wide range of activities. For example with a new diet, can cognitive changes be attributed to the food that was no longer being eaten or the new food? Or a combination of the two? However simply to demonstrate that older adults can experience increased structure in certain brain regions is an important contribution to our understanding of the human brain.