Brain imaging studies find that mindfulness training can change the human brain’s functional connectivity. That is, the degree to which various brain regions jointly covary in their activity. However, the causal direction of brain connectivity remains unknown due to the limitations of functional connectivity analyses that only indicate if synchrony occurs, but cannot clarify the brain regions that initiate these changes.
Effective connectivity analyses is a newer method that may be able to uncover the temporal sequence of brain functional activity
Santarnecchi et al. [Journal of Neuroscience Research] tested the effects of MBSR on brain activity compared to an inactive control group of healthy participants using fMRI functional and effective connectivity analyses of brain regions in a randomized controlled trial.
The researchers randomly assigned 46 meditation-naïve Italian adults (average age=30 years; 52% female) to either MBSR program or a wait-list control. MBSR was delivered in the standard 8-week group-based format that included 45 minutes of daily homework and a 7-hour retreat.
All participants underwent neuroimaging before and after the intervention period, both during a resting state and while engaging in mindfulness of the breath and body. Pre-treatment conditions and the post-treatment control condition were told to attend to sensations of breathing and bodily sensations, while the post-treatment MBSR condition was instructed to meditate as they had been taught in MBSR.
Imaging results showed that MBSR resulted in significant decreases in local regional homogeneity in the right anterior putamen and the right insula during the resting state compared to controls.
MBSR also resulted in a significant decrease in right cerebellum regional homogeneity during mindfulness practice compared to controls. Regional homogeneity is a measure of the degree to which adjacent fMRI voxels within a brain region show synchronous activity.
The effective connectivity analysis using the above regions as seeds revealed a number of functional changes as a result of mindfulness training:
During the resting state, the anterior cingulate cortex decreased its excitatory influence on the right anterior putamen.
During mindfulness practice, the right cerebellum decreased its inhibitory effect on the right posterior putamen and right orbitofrontal cortex; the left posterior putamen decreased its excitatory influence on the right cerebellum; and the left somatosensory cortex increased its inhibitory effect on the right cerebellum.
The role of the putamen is prominent in several of these findings. This makes sense as the anterior putamen is involved in executive functioning and attention, while the posterior putamen is involved in somatosensory processing. These processes play key roles in the attentional control and awareness of bodily sensations that are central to mindfulness.
This study uses a novel brain imaging methodology and shows that MBSR alters the influences of the anterior cingulate and orbitofrontal cortexes on the putamen, and the putamen on the cerebellum. Findings highlight the temporal patterns that play a key role in brain activity correlated with mindfulness training.
The study interpretation is limited by not including respiration and cardiac rates as covariates, as these might affect changes in the blood oxygenation levels that generate fMRI images.
Santarnecchi, E., Egiziano, E., D’Arista, S., Gardi, C., Romanella, S. M., Mencarelli, L., Rossi, S., Reda, M., & Rossi, A. (2021). Mindfulness-based stress reduction training modulates striatal and cerebellar connectivity. Journal of Neuroscience Research.
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