Keeping weight off: Mindfulness-Based Stress Reduction alters amygdala functional connectivity during weight loss maintenance in a randomized control trial.

Obesity is associated with significant comorbidities and financial costs. While behavioral interventions produce clinically meaningful weight loss, weight loss maintenance is challenging. The objective was to improve understanding of the neural and psychological mechanisms modified by mindfulness that may predict clinical outcomes. Individuals who intentionally recently lost weight were randomized to Mindfulness-Based Stress Reduction (MBSR) or a control healthy living course. Anthropometric and psychological factors were measured at baseline, 8 weeks and 6 months. Functional connectivity (FC) analysis was performed at baseline and 8 weeks to examine FC changes between regions of interest selected a priori, and independent components identified by independent component analysis. The association of pre-post FC changes with 6-month weight and psychometric outcomes was then analyzed. Significant group x time interaction was found for FC between the amygdala and ventromedial prefrontal cortex, such that FC increased in the MBSR group and decreased in controls. Non-significant changes in weight were observed at 6 months, where the mindfulness group maintained their weight while the controls showed a weight increase of 3.4% in BMI. Change in FC at 8-weeks between ventromedial prefrontal cortex and several ROIs was associated with change in depression symptoms but not weight at 6 months. This pilot study provides preliminary evidence of neural mechanisms that may be involved in MBSR's impact on weight loss maintenance that may be useful for designing future clinical trials and mechanistic studies.

Increased wiring cost during development is driven by long-range cortical, but not subcortical connections.

The brain undergoes a protracted, metabolically expensive maturation process from childhood to adulthood. Therefore, it is crucial to understand how network cost is distributed among different brain systems as the brain matures. To address this issue, here we examined developmental changes in wiring cost and brain network topology using resting-state functional magnetic resonance imaging (rsfMRI) data longitudinally collected in awake rats from the juvenile age to adulthood. We found that the wiring cost increased in the vast majority of cortical connections but decreased in most subcortico-subcortical connections. Importantly, the developmental increase in wiring cost was dominantly driven by long-range cortical, but not subcortical connections, which was consistent with more pronounced increase in network integration in the cortical network. These results collectively indicate that there is a non-uniform distribution of network cost as the brain matures, and network resource is dominantly consumed for the development of the cortex, but not subcortex from the juvenile age to adulthood.

Relationship of mindful awareness to neural processing of angry faces and impact of mindfulness training: A pilot investigation.

Mindfulness is paying attention, non-judgmentally, to experience in the moment. Mindfulness training reduces depression and anxiety and influences neural processes in midline self-referential and lateralized somatosensory and executive networks. Although mindfulness benefits emotion regulation, less is known about its relationship to anger and the corresponding neural correlates. This study examined the relationship of mindful awareness and brain hemodynamics of angry face processing, and the impact of mindfulness training. Eighteen healthy volunteers completed an angry face processing fMRI paradigm and measurement of mindfulness and anger traits. Ten of these participants were recruited from a Mindfulness-Based Stress Reduction (MBSR) class and also completed imaging and other assessments post-training. Self-reported mindful awareness increased after MBSR, but trait anger did not change. Baseline mindful awareness was negatively related to left inferior parietal lobule activation to angry faces; trait anger was positively related to right middle frontal gyrus and bilateral angular gyrus. No significant pre-post changes in angry face processing were found, but changes in trait mindful awareness and anger were associated with sub-threshold differences in paralimbic activation. These preliminary and hypothesis-generating findings, suggest the analysis of possible impact of mindfulness training on anger may begin with individual differences in angry face processing.

Mapping resting-state brain networks in conscious animals.

In the present study we mapped brain functional connectivity in the conscious rat at the "resting state" based on intrinsic blood-oxygenation-level dependent (BOLD) fluctuations. The conscious condition eliminated potential confounding effects of anesthetic agents on the connectivity between brain regions. Indeed, using correlational analysis we identified multiple cortical and subcortical regions that demonstrated temporally synchronous variation with anatomically well-defined regions that are crucial to cognitive and emotional information processing including the prefrontal cortex (PFC), thalamus and retrosplenial cortex. The functional connectivity maps created were stringently validated by controlling for false positive detection of correlation, the physiologic basis of the signal source, as well as quantitatively evaluating the reproducibility of maps. Taken together, the present study has demonstrated the feasibility of assessing functional connectivity in conscious animals using fMRI and thus provided a convenient and non-invasive tool to systematically investigate the connectional architecture of selected brain networks in multiple animal models.

A dynamic fMRI study of illusory double-flash effect on human visual cortex.

Functional MRI (fMRI) combined with the paired-stimuli paradigms (referred as dynamic fMRI) was used to study the "illusory double-flash" effect on brain activity in the human visual cortex. Three experiments were designed. The first two experiments aimed to examine the cross-modal neural interaction between the visual and auditory sensory systems caused by the illusory double-flash effect using combined auditory (beep sound) and visual (light flash) stimuli. The fMRI signal in the visual cortex was significantly increased in response to the illusory double flashes compared to the physical single flash when the inter-stimuli delay between the auditory and visual stimuli was 25 ms. This increase disappeared when the delay was prolonged to approximately 300 ms. These results reveal that the illusory double-flash effect can significantly affect the brain activity in the visual cortex, and the degree of this effect is dynamically sensitive to the inter-stimuli delay. The third experiment was to address the spatial differentiation of brain activation in the visual cortex in response to the illusory double-flash stimulation. It was found that the illusory double-flash effect in the human visual cortex is much stronger in the periphery than the fovea. This finding suggests that the periphery may be involved in high-level brain processing beyond the retinotopic visual perception. The behavioral measures conducted in this study indicate an excellent correlation between the fMRI results and behavioral performance. Finally, this work demonstrates a unique merit of fMRI for providing both temporal and spatial information regarding cross-modal neural interaction between different sensory systems.

Probing fast neuronal interaction using fMRI.

The paired-stimuli paradigms were used to study cross-modal neural interactions between the visual and auditory systems in human. It was found that the primary visual cortex was actively involved in the 'illusory double-flash' phenomenon. The similar paradigms were used to study the influence of MR scanner noise on human visual activities from the perspective of neural interaction. The results reveal that the gradient acoustic noise does interfere with the neural behavior in human visual cortex.