Over the past decade mind and body practices, such as yoga and meditation, have raised interest in different scientific fields; in particular, the physiological mechanisms underlying the beneficial effects observed in mediators have been investigated. Neurosurgical studies have studied the effects of meditation on brain structure and function and findings have helped clarify the biological underpinnings of the positive effects of meditation practice and the possible integration of this technique in standard therapy. The large amount of data collected thus far allows drawing some conclusions about the neural effects of meditation practice. In the present study we used activation likelihood estimation (ALE) analysis to make a coordinate-based meta-analysis of neurosurgical data on the effects of meditation on brain structure and function. Results indicate that meditation leads to activation in brain areas involved in processing self-relevant information, self-regulation, focused problem-solving, adaptive behavior, and interception. Results also show that meditation practice induces functional and structural brain modifications in expert mediators, especially in areas involved in self-referential processes such as self-awareness and self-regulation. These results demonstrate that a biological substrate underlies the positive pervasive effect of meditation practice and suggest that meditation techniques could be adopted in clinical populations and to prevent disease.

1. Introduction

Mind and body practices such as yoga, meditation, progressive relaxation, or guided imagery use mental and physical abilities to improve health and well-being. Over the past decade these practices have received increasing attention in different fields of study in which the physiological mechanisms underlying the beneficial effects observed in trained individuals have been investigated. Increased knowledge about the physiological effects of mind and body practices makes it possible to explore their therapeutic potential, identify adverse effects, and safely integrate these techniques into standard therapeutic approach.

Meditation is a complex process aimed at self-regulating the body and mind and is often associated with psychological and neurophysiology’s modifications [1]. Meditation practices can be oriented toward the concentration of attention on a particular external, corporal, or mental object, while ignoring all irrelevant stimuli (focused attention meditation), or toward techniques that try to enlarge the attention al focus to all incoming sensations, emotions, and thoughts from moment to moment without focusing on any of them (open monitoring meditation) [2]. In any case, most meditation approaches use both types of practices complementary

Meditation practice has been found to promote well-being by fostering cognitive and emotional processes Specifically, it has been found to improve working memory and attention al processes as well as perceptual abilities t has also been found to promote prosocial behavior and emotional regulation The potential contribution of meditation to cognitive and emotional processes can be appreciated in the context of the model proposed by Lutz and colleagues [These authors posited that meditation practice induces enhancement of at least four different abilities: sustained attention, monitoring faculty (to detect mind wandering), the ability to disengage from a distracting object without further involvement (attention-al switching), and the ability to redirect focus to the chosen object (selective attention). A recent systematic review by Chiesa and colleagues allowed drawing some important conclusions about the positive effect of meditation on cognitive functions. Executive functions, attention, and memory were the main targets of meditation practice. In particular, as compared to the control group, mediators showed improved sustained attention conflict monitoring and reduced attention-al blink Mediators also performed better than controls in the classical working memory paradigms Concerning memory, significant improvement was found in meta-awareness and in specific autobiographical memories after meditation training. Partner and colleagues also found that meditation groups showed reduced interference from unpleasant pictures, suggesting that meditation also has a positive effect in decreasing emotional interference during performance of a cognitive task.

Interestingly, the current literature suggests that meditation has a potential effect on age-related cognitive decline [22, 23], probably due to the regulation of glucocorticosteroids, inflammation, and serotonin metabolism [23]. Furthermore, it has been hypothesized that the stress reduction promoted by meditation contrasts hippocampus vulnerability to neurotoxin and leads to increased hippocampus grey matter volume due to neuron preservation and/or iatrogenesis. Meditation has also been found to reduce a number of psychological and physical symptoms in clinical populations King and coworkers found that mindfulness-based cognitive therapy was an acceptable brief intervention therapy for combating PTSD: indeed, it reduced avoidance symptoms and PTSD cognition. There is also evidence that, compared to standard care, mindfulness-based cognitive therapy almost halves the risk of relapse in people who are currently well but who have experienced at least three prior episodes of depression and is comparable to antidepressant medication in reducing risk of relapse

The effects of meditation on brain structure and function have received increasing attention in neurosurgical studies (MRI, fMRI, and PET) and the number of published studies is steadily growing [32]. Specifically, the findings of neurosurgical investigations have allowed linking the positive effects of meditation to specific brain modifications. Neurosurgical studies of brain modification can be roughly divided into those investigating (1) nonfunctional correlates of meditation, (2) nonfunctional modifications after meditation training, and (3) structural brain modifications in expert mediators.

Functional studies on the brain correlates of meditation have assessed neural activation during meditation by requiring participants to undergo fMRI scans during meditation tasks. These studies have reported increased activation in areas associated with attention, mind wandering, retrieval of episodic memories, and emotional processing during meditation Specifically, increased activation in the prefrontal cortex parietal areas middle cingulate cortex, and hippocampus and parahippocampal formations has been reported.

Studies of functional brain modifications after meditation training have focused on functional and the metabolic changes after meditation training and/or in expert mediators compared with control participants. These studies adopted different paradigms : the effective Stoop task pain-related tasks , attention al paradigms emotional provocation and meditation tasks [. The results of these studies are very intriguing because they shed more light on the possible link between nonfunctional changes and the positive effect of meditation on different aspects of cognitive and emotional processes, such as perceptual and attention al processes as well as social behavior and emotional regulation