Meditation experience is associated with increased cortical thickness
Lazar, Sara W.; Kerr, Catherine E.; Wasserman, Rachel H.; Gray, Jeremy R.; Greve, Douglas N.; Treadway, Michael T.; McGarvey, Metta; Quinn, Brian T.; Dusek, Jeffery A.; Benson, Herbert; Rauch, Scott L.; Moore, Christopher I.; Fischl, Bruce
Neuroreport, November 28, 2005; 16(17): 1893-1897

This group of researchers measured the the thickness of the cerebral cortex in 20 participants with extensive Insight meditation practice and matched controls with magnetic resonance imaging. Insight meditation is a type of meditation involving focused attention on internal experiences. The meditators had an average of nine years of practice of about forty minutes a day. Particular cortical areas were thicker in meditators than in controls, especially those associated with attention, interoception, and sensory processing such as the prefrontal cortex, which controls attention and modulation of emotion and its expression, and the right anterior insula, which is involved in empathy and internal monitoring of the body. The differences were greatest in older participants, who had more meditation experience, suggesting meditation may have caused this difference to some extent. It also implies that meditation may offset the thinning of the cerebral cortex that can occur with age.

Mindfulness practice leads to increases in regional brain gray matter density
Britta K. Hölzel, James Carmody, Mark Vangel, Christina Congleton, Sita M. Yerramsetti, Tim Gard, Sara W. Lazar
Psychiatry Research: Neuroimaging, January 30, 2011; 191(1): 36-43.

Mindfulness-Based Stress Reduction (MBSR) is one of the most widely used mindfulness training programs and has been reported to produce positive effects on psychological well-being and to ease the symptoms of a number of disorders. This controlled longitudinal study used anatomical magnetic resonance imaging and voxel-based morphometry to compare the brain gray matter concentration of 16 healthy, meditation novices before and after an 8-week MBSR program. This group was also compared to 17 controls. Gray matter concentration increased in the left hippocampus, the posterior cingulate cortex, the temporo-parietal junction, and the cerebellum in the MBSR group compared with the controls. The results suggest that participation in MBSR is associated with changes in gray matter concentration in brain regions involved in learning and memory, emotion regulation, self-referential processing, and perspective taking.

Functional brain mapping of the relaxation response and meditation
Lazar, Sara W.; Bush, George; Gollub, Randy L.; Fricchione, Gregory L.; Khalsa, Gurucharan; Benson, Herbert
Neuroreport, May 15, 2000; 11(7): 1581-1585.

This experiment defined meditation as a “conscious mental process that induces a set of integrated physiologic changes termed the relaxation response.” It used functional magnetic resonance imaging (fMRI) to identify and characterize the brain regions that are active during a simple form of meditation. Significant increases in signal were observed in the hippocampus, parahippocampus, pregenual anterior cingulate cortex, temporal lobe, dorsolateral prefrontal and parietal cortices, striatum, and pre- and post-central gyri during meditation. Signal decreases were also found, although the researchers believe they were probably secondary to the cardiorespiratory changes that often accompany meditation. The results indicate that the practice of meditation activates neural structures involved in attention and control of the autonomic nervous system.

The unique brain anatomy of meditation practitioners: Alterations in cortical gyrification
Eileen Luders, Florian Kurth, Emeran A. Mayer, Arthur W. Toga, Katherine L. Narr, Christian Gaser
Frontiers in Human Neuroscience, 2012; 6

This study by Eileen Luders, an assistant professor at the UCLA Laboratory of Neuro Imaging, and her colleagues built on previous research that found that long-term meditators have larger amounts of gyrification than people who do not meditate. Gyrification is a folding of the cerebral cortex, the outermost layer of the brain. The cerebral cortex plays a key role in memory, thought, consciousness, and attention. More folding may mean faster and better information processing. In this experiment, they compared the MRI scans of 23 meditators with those of 16 controls that were matched for age, gender, and handedness. The meditators had an average of 20 years of experience of a variety of types of meditation such as Samatha, Zen, Vipassana, and more. They had greater gyrification than control subjects over a large part of the cortex, including the left and right anterior dorsal insula, the left precentral gyrus, the right cuneus, and the right fusiform gyrus. The more years a person had been meditating, the greater the extent of gyrification in the insula, which is thought to be a focal point for the integration of affective, autonomic, and cognitive processes of the brain. While many factors may be involved in these effects, the researchers say, “"The positive correlation between gyrification and the number of practice years supports the idea that meditation enhances regional gyrification." They may also provide further evidence of the brain’s ability to adapt to environmental changes.

Pain sensitivity and analgesic effects of mindful states in Zen meditators: A cross-sectional study
Grant, Joshua A., Rainville, Pierre
Psychosomatic Medicine, 2009; 71: 106-114

For this study, the scientists compared 13 Zen meditators with a minimum of 1,000 hours of practice to 13 non-meditators in their reaction to a pain when a computer-controlled heating plate was pressed to their calves at temperatures ranging from 43 degrees Celsius up to 53 degrees Celsius, depending on each participant's sensitivity. While quite a few of the meditators tolerated the maximum temperature, even without meditating at the time, all control subjects were well below 53 degrees Celsius. Overall, Zen meditators experienced an 18 percent reduction in pain intensity. During meditation-like conditions, it appeared meditators further reduced their pain partly through slower breathing: an average of 12 breaths per minute versus 15 breaths for non-meditators. Slower breathing may have had an influence because it keeps the body more relaxed.

Meditation states and traits: EEG, ERP, and neuroimaging studies
Cahn, B. Rael; Polich, John
Psychological Bulletin, Mar 2006; 132(2): 180-211
In this review of neuroelectric and imaging studies of meditation, Cahn and Polich saw that brain signals measured be electroencelphalogram (EEG) were slower overall after meditation. Activation of theta and alpha waves, both slow waves, was related to proficiency of practice. Some studies also indicated that practice changes attentional allocation and increased regional cerebral blood flow during meditation. Changes were seen in the anterior cingulate cortex and dorsolateral prefrontal areas in particular. Although results have been variable, they are beginning to demonstrate consistent outcomes for research and clinical applications. Psychological and clinical effects of meditation were also found.

Awareness of subtle emotional feelings: A comparison of long-term meditators and non-meditators<
Nielsen, L, & Kaszuiak, AW
Emotion, 6: 392-405
In this study of Zen and Mindfulness meditators with over ten years of experience, researchers report higher emotional clarity with lower physiological and experienced arousal as well as more subtle positive facial expression in response to masked emotional pictures. This observation is consistent with regulation of emotion early in the emotion process. Longer practice of meditation enabled a shift from attachment and reactivity to a more steady emotional response. In the practices studied, this transformation occurred over many years. Initially, an increase in attention, awareness of bodily feelings, use of thought to regulate emotional expression, and physiological reactivity to emotional stressors is seen. In later years, emotional clarity increases, and explicit attention to emotion may no longer be as needed. The clarity achieved may confer emotional regulatory skill, and attention to subtle emotional cues may have become automated.

A comparative randomised controlled trial of the effects of Brain Wave Vibration training, Iyengar yoga, and Mindfulness on mood, well-being, and salivary cortisol
Deborah Bowden, Claire Gaudry, Seung Chan An, and John Gruzelier
Evidence-Based Complementary and Alternative Medicine, Volume 2012, Article ID 234713: 13 pages

This randomised trial compared the effects of Brain Wave Vibration (BWV) training, which involves rhythmic yoga-like meditative exercises, with Iyengar yoga and Mindfulness. Iyengar provided a contrast for the physical components and Mindfulness for the “mental” components of BWV. Thirty-five healthy adults completed ten 75-minute classes of BWV, Iyengar, or Mindfulness over five weeks. Participants were assessed at pre- and postintervention for mood, sleep, mindfulness, absorption, health, memory, and salivary cortisol. Better overall mood and vitality followed both BWV and Iyengar training, while the BWV group alone had improved depression and sleep latency. Mindfulness produced a comparatively greater increase in absorption. All interventions improved stress and mindfulness, while no changes occurred in health, memory, or salivary cortisol. In conclusion, increased well-being followed training in all three practices, increased absorption was specific to Mindfulness, while BWV was unique in its benefits to depression and sleep latency.