Key result
Global signal regression diminishes connectivity clusters while task paradigm regression yields differences reflecting neuronal activity.
Why the study?
The lack of a clear methodology for analyzing insular functional connectivity during acute pain complicates interpretation of fcMRI data, particularly regarding the effects of global signal and task paradigm regression.
Observational
In fcMRI analysis of acute pain, the choice of global signal regression and task paradigm regression significantly impacts the resulting functional connectivity maps of the insula.
Insula fcMRI maps in acute pain require method-specific caution; leaves open optimal regression standardization for reliable neuronal insights.
The insula is uniquely located between the temporal and parietal cortices, making it anatomically well-positioned to act as an integrating center between the sensory and affective domains for the processing of painful stimulation. This can be studied through resting-state functional connectivity (fcMRI) imaging; however, the lack of a clear methodology for the analysis of fcMRI complicates the interpretation of these data during acute pain. Detected connectivity changes may reflect actual alterations in low-frequency synchronous neuronal activity related to pain, may be due to changes in global cerebral blood flow or the superimposed task-induced neuronal activity. The primary goal of this study was to investigate the effects of global signal regression (GSR) and task paradigm regression (TPR) on the changes in functional connectivity of the left (contralateral) insula in healthy subjects at rest and during acute painful electric nerve stimulation of the right hand. The use of GSR reduced the size and statistical significance of connectivity clusters and created negative correlation coefficients for some connectivity clusters. TPR with cyclic stimulation gave task versus rest connectivity differences similar to those with a constant task, suggesting that analysis which includes TPR is more accurately reflective of low-frequency neuronal activity. Both GSR and TPR have been inconsistently applied to fcMRI analysis. Based on these results, investigators need to consider the impact GSR and TPR have on connectivity during task performance when attempting to synthesize the literature.
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Ibinson et al. (2015) conducted an observational in Acute experimental pain. Global signal regression (GSR) and task paradigm regression (TPR) was evaluated on Changes in functional connectivity of the left (contralateral) insula. Global signal regression reduced the size and statistical significance of connectivity clusters, while task paradigm regression yielded connectivity differences reflective of neuronal activity.
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