Editorial: What can Neuroscience Learn from Contemplative Practices?

Contemplative practices like meditation and mindfulness have recently gained increased acceptance in science and clinical practice, although a number of issues related to their phenomenology and to experimental designs still remain (Dahl et al., 2015).

Meditation and mindfulness practices can also generate intense and unusual experiences and altered states of consciousness, such as states of reduced phenomenal content, or absorptions (Lutz et al., 2007). These are akin to states of deep relaxation, or even deep sleep, but without actually sleeping. They can have other unusual features, such as alterations in the sense of time and space (Berkovich-Ohana et al., 2013), or spontaneous perceptions of light patterns (Lindahl et al., 2014). An intuitive, but arguable, idea is that most of these states should lead to global decreases in cortical activity (Hinterberger et al., 2014;Berkovich-Ohana et al., 2015), or at least to decreases in the areas related to spontaneous thinking (Brewer et al., 2011). Perhaps even more interesting are the states of reduced phenomenal content accompanied by increased awareness. The subjects report experiencing their consciousness as being relatively "pure, " an awareness without a content. These may emerge at first as brief interruptions in one's usual stream of consciousness during meditation (Baars, 2013), then get progressively more stabilized and longer lasting, until eventually one can find the "pure" nondual awareness present as a background context of all one's experiences, including dreaming and deep sleep (Travis et al., 2002;Ferrarelli et al., 2013;Josipovic, 2014;Thompson, 2014). Baars (2013) discusses some possible ways of approaching the research of these states. Expanding the neuroscience view of consciousness to include certain perspectives found in contemplative traditions may help to resolve some of the current impasses in debates about the neural correlates of consciousness (Block, 2007;Cohen and Dennett, 2011;Lau and Rosenthal, 2011;Baars et al., 2013).

ONGOING CHALLENGES
One of the most challenging issues for meditation studies is the lack of accurate indices of subjects' experience during meditation, independent from subjects' reports. Several neurophysiological measures have been proposed over the years, however, it is not likely that any single measure can adequately capture the complexity of meditation experience (Davis and Vago, 2014). An interesting recent development are the attempts to obtain experience sampling data and provide neurofeedback via wearable devices and cell phones, as an adjunct to meditation training. As Brandmeyer and Delorme (2013) point out such attempts still await further scientific developments in sensor technology.
Several persistent methodological issues have plagued meditation research studies since the early days (Nash and Newberg, 2013;Dahl et al., 2015;Tang et al., 2015a). Reliance on self-report measures with inadequate controls for placebo effect and demand characteristic can make the results questionable. Obtaining neuroimaging and other physiological measures that parametrically co-vary with self-report measures can remedy this and facilitate assessing the meaning of results. However, more direct systematic replications of results are needed. Replication attempts can be compromised when subjects or researchers in the original and replication studies belong to schools of contemplative practice that define the same meditation differently. Largely due to funding limitations, most meditation studies are still of a pilot kind, with a small number of self-selected subjects, utilizing within-subject or cross-sectional designs, and often with inadequate control groups for the placebo effect. Large scale, randomized, longitudinal studies with active control groups can overcome some of these shortcomings (Tang et al., 2015a).

DIFFICULTY IN RELATING TO TRADITIONAL VIEWS
The extraordinary multiplicity of meditation techniques and seemingly contradictory effects they produce pose a significant challenge for researchers. While the current research-oriented taxonomies have addressed this problem through categorizing meditation techniques into two or three major styles (Lutz et al., 2008;Josipovic, 2010;Travis and Shear, 2010), further optimizing is needed for such taxonomies to be more accurate and comprehensive (Nash and Newberg, 2013;Newberg, 2014;Dahl et al., 2015).
Contrary to popular "one-size-fits-all" approaches and advertisements, different meditations can have differential effects depending on one's psychological and physical makeup, and on the stage of one's practice. Adverse effects of meditation and mindfulness, which are often discounted in traditional contexts, can be significant and are only recently being studied in a systematic way (Garland et al., 2015).
Taking meditation out of its cultural, religious, and philosophical contexts may miss the influences that these contexts can have on the observed results. Future research will need to include spiritual and religious motivations, ethical concerns, as well as interpersonal and cultural contexts (Nash and Newberg, 2013;Dahl et al., 2015). The views on the overall goal of contemplative practice can be diametrically opposed both between different traditions and within the sects of the same tradition, and can significantly influence how individuals practice, which experiences they cultivate, and which ones get selected for research (Davis and Vago, 2014).
Science alone, in its present form, may not be able to answer ontological and metaphysical questions about the nature of consciousness that are the focus of contemplative traditions . New scientific methods, and a more integrated approach that combines humanities and sciences, may be necessary to encompass the vastness of human experience that meditations can lead to.