Absence of structural brain changes from mindfulness-based stress reduction: Two combined randomized controlled trials.

Studies purporting to show changes in brain structure following the popular, 8-week mindfulness-based stress reduction (MBSR) course are widely referenced despite major methodological limitations. Here, we present findings from a large, combined dataset of two, three-arm randomized controlled trials with active and waitlist (WL) control groups. Meditation-naïve participants (n = 218) completed structural magnetic resonance imaging scans during two visits: baseline and postintervention period. After baseline, participants were randomly assigned to WL (n = 70), an 8-week MBSR program (n = 75), or a validated, matched active control (n = 73). We assessed changes in gray matter volume, gray matter density, and cortical thickness. In the largest and most rigorously controlled study to date, we failed to replicate prior findings and found no evidence that MBSR produced neuroplastic changes compared to either control group, either at the whole-brain level or in regions of interest drawn from prior MBSR studies.

Color Tuning of Face-Selective Neurons in Macaque Inferior Temporal Cortex.

What role does color play in the neural representation of complex shapes? We approached the question by measuring color responses of face-selective neurons, using fMRI-guided microelectrode recording of the middle and anterior face patches of inferior temporal cortex (IT) in rhesus macaques. Face-selective cells responded weakly to pure color (equiluminant) photographs of faces. But many of the cells nonetheless showed a bias for warm colors when assessed using images that preserved the luminance contrast relationships of the original photographs. This bias was also found for non-face-selective neurons. Fourier analysis uncovered two components: the first harmonic, accounting for most of the tuning, was biased toward reddish colors, corresponding to the L>M pole of the L-M cardinal axis. The second harmonic showed a bias for modulation between blue and yellow colors axis, corresponding to the S-cone axis. To test what role face-selective cells play in behavior, we related the information content of the neural population with the distribution of face colors. The analyses show that face-selective cells are not optimally tuned to discriminate face colors, but are consistent with the idea that face-selective cells contribute selectively to processing the green-red contrast of faces. The research supports the hypothesis that color-specific information related to the discrimination of objects, including faces, is handled by neural circuits that are independent of shape-selective cortex, as captured by the multistage parallel processing framework of IT (Lafer-Sousa and Conway, 2013).

The relationship between mindfulness and objective measures of body awareness: A meta-analysis.

Although awareness of bodily sensations is a common mindfulness meditation technique, studies assessing the relationship between mindfulness and body awareness have provided mixed results. The current study sought to meta-analytically examine the relationship between mindfulness operationalized as a dispositional trait or a construct trained through short- (i.e., randomized controlled trials [RCTs]) or long-term mindfulness meditation practice with objective measures of body awareness accuracy. PubMed, Web of Science, PsycINFO, and Scopus were searched. Studies were eligible if they reported the association between mindfulness and body awareness, were published in English, and included adults. Across 15 studies (17 independent samples), a small effect was found linking mindfulness with greater body awareness accuracy (g = 0.21 [0.08, 0.34], N = 879). When separated by study design, only RCTs continued to show a significant relationship (g = 0.20, [0.02, 0.38], k = 7, n = 505). Heterogeneity of effects was low (I2 < 25%), although with wide confidence intervals. Effects were not moderated by study quality. Low fail-safe N estimates reduce confidence in the observed effects. Results suggest a small but potentially detectable relationship between mindfulness and body awareness accuracy. Future investigations could examine individual differences in body awareness as a mechanism within mindfulness interventions.

Still facial photographs of long-term meditators are perceived by naïve observers as less neurotic, more conscientious and more mindful than non-meditating controls.

The impact of meditation training on self-report psychological variables is well-established. Although meditation training is purported to have interpersonal impacts, whether naïve observers perceive differences associated with long- and short-term meditation training is largely unknown. The current study provided a stringent test of this possibility through observer ratings of a very thin slice of expressive behavior: still photographs. Photographs were drawn from a larger study investigating differences between long-term meditators (LTM) and meditation naïve participants (MNP) who were exposed to one of three experimental conditions. Photographs of ninety-nine targets (16 LTMs, 83 MNPs) were taken at baseline, prior to the randomization of MNPs to an eight-week mindfulness meditation course (mindfulness-based stress reduction; n = 27), an active control comparison condition (health enhancement program; n = 29), or a waitlist control group (n = 27) and again after the training period. Pre- and post-intervention photographs were then rated by 25 meditation teachers and 86 undergraduate raters on five domains theoretically linked to meditation training. Results indicated that relative to MNPs, LTMs were rated as less neurotic and more conscientious, mindful, and "comfortable in their own skin" at baseline (ds = 0.61 to 0.70, ps < .050), although not more agreeable or attractive. Results were largely unchanged when controlling for five observable confounds (age, gender, race/ethnicity, body mass index, attractiveness). No evidence was found supporting experimental effects of short-term meditation training on observer ratings. Thus, it seems that if meditation is associated with observable differences in facial behavior, effects may be limited to long-term training.