Investigating Effects of Mindfulness Training on DMN Connectivity and Dynamics

Background and rationale

Major Depression is one of the leading contributors to the burden of disease world-wide. While there are established treatments, a considerable proportion of patients do not respond sufficiently. About a third of people who suffer from depression develop an increasingly chronic and recurrent course that is accompanied by progressive changes in brain structure and functioning. These changes act to prevent recovery and play an important role in conferring an increased risk for associated physical and neurodegenerative disorders.

Training in mindfulness helps patients recognize and disengage from the maladaptive and habitual patterns of thinking that maintain the disorder and has been shown to have promising effects in the treatment of such persistent courses. Mindfulness-Based Cognitive Therapy (MBCT), a standard MBI consisting of eight weekly sessions, is now a recommended treatment for the prevention of relapse in highly recurrent courses of depression.

However, recent research indicates that beneficial effects are contingent on sustained practice and utilization of mindfulness skills beyond the actual intervention periods. There is now an increasing awareness of the need to support patients in establishing a sustained practice of mindfulness. Yet despite the fact that this need is now widely acknowledged, there are currently no established approaches to support patients in sustained practice and it remains unclear in how far, and at what levels, sustained practice may lead to visible changes in underlying neurobiological vulnerabilities. While standard MBIs have been shown to have significant beneficial effects in patients with persistent forms of depression, there is still a considerable proportion of patients who do not respond sufficiently - current trials suggest a response rate of about 50%. Few studies have investigated reversibility of neurobiological vulnerabilities in depression. However, research in healthy meditators suggests that sustained practice in mindfulness may have promising potential for this purpose. Establishing approaches to support patients in sustained practice and understanding its effects on neurobiological vulnerabilities therefore represents an important step in improving MBIs for this group.

Previous research has indicated that the psychological maintenance mechanisms that hold persistent forms of depression in place are associated with significant changes in the connectivity and dynamics of the DMN, a large distributed network of interacting brain regions that serves to imbue present moment experience with memory content and becomes active when people engage in mind wandering and other forms of task-unrelated thinking such as rumination. Research in patients with depression has shown that depression is characterised by significant deficits in suppressing DMN activity during performance of common working memory and other executive tasks. Furthermore, there is now considerable evidence for aberrations in connectivity within and from this network to other regions of the brain that are relevant in the regulation of attention and emotions.