Low back pain and resting-state functional connection
The default mode network is a key area in the resting state, involving the posterior cingulate cortex, precuneus, medial prefrontal and lateral temporal cortices, and is characterized by balanced positive and negative connections classified as the "hubs" of structural and functional connectivity in brain studies.
Resting-state functional connectivity MRI is based on the observation that brain regions exhibit correlated slow fluctuations at rest, and has become a widely used tool for investigating spontaneous brain activity.
Functional magnetic resonance imaging studies have shown that the insular cortex has a significant role in pain identification and information integration, while the default mode network is associated with cognitive and memory-related aspects of pain perception.
However, changes in the functional connectivity between the default mode network and insula during pain remain unclear.
Shanshan Zhang and co-workers from Zhujiang Hospital, Southern Medical University in China compared the differences in the functional activity and connectivity of the insula and default mode network between the baseline and pain condition induced by intramuscular injection of hypertonic saline in healthy subjects.
Compared with the baseline, the insula was more functionally connected with the medial prefrontal and lateral temporal cortices, whereas there was lower connectivity with the posterior cingulate cortex, precuneus and inferior parietal lobule in the pain condition.
In addition, compared with baseline, the anterior cingulate cortex exhibited greater connectivity with the posterior insula, but lower connectivity with the anterior insula, during the pain condition.
This is a resting-state functional connectivity map showing positively (A) and negatively (B) correlated voxels for seed regions of interest (mPFC, PCC, LTC, aIC and pIC) in low back pain subjects (P < 0.001, K ≥ 10, uncorrected). Color area: Regions with differences between pain state and normal. mPFC: Medial prefrontal cortex; PCC: posterior cingulate cortex; LTC: lateral temporal cortex; aIC: anterior insula; pIC: posterior insula.
Credit: Neural Regeneration Research
These data indicate that experimental low back pain led to dysfunction in the connectivity between the insula and default mode network resulting from an impairment of the regions of the brain related to cognition and emotion, suggesting the importance of the interaction between these regions in pain processing.
The relevant paper has been published in Neural Regeneration Research (Vol. 9, No. 2, 2014).