Chronic itch, a highly debilitating condition, has received relatively little attention in the neuroimaging literature. Recent studies suggest that brain regions supporting itch in chronic itch patients encompass sensorimotor and salience networks, and corticostriatal circuits involved in motor preparation for scratching. However, how these different brain areas interact with one another in the context of itch is still unknown. We acquired BOLD fMRI scans in 14 atopic dermatitis patients to investigate resting-state functional connectivity before and after allergen-induced itch exacerbated the clinical itch perception in these patients. A seed-based analysis revealed decreased functional connectivity from baseline resting state to the evoked-itch state between several itch-related brain regions, particularly the insular and cingulate cortices and basal ganglia, where decreased connectivity was significantly correlated with increased levels of perceived itch. In contrast, evoked itch increased connectivity between key nodes of the frontoparietal control network (superior parietal lobule and dorsolateral prefrontal cortex), where higher increase in connectivity was correlated with a lesser increase in perceived itch, suggesting that greater interaction between nodes of this executive attention network serves to limit itch sensation via enhanced top-down regulation. Overall, our results provide the first evidence of itch-dependent changes in functional connectivity across multiple brain regions.
Keywords: AD, atopic dermatitis; ASL, arterial spin labeling; Atopic dermatitis; BA, Brodmann area; BOLD, blood-oxygen-level dependent; DMN, default mode network; ECG, electrocardiography; Eczema; GLM, general linear model; ITCH, evoked itch resting-state scan; Insula; L, left; MNI, Montreal Neurological Institute; MR, magnetic resonance; PCC, posterior cingulate cortex; PET, positron emission tomography; PMC, premotor cortex; Pruritus; Putamen; R, right; REST, baseline resting-state scan; S1/M1, primary sensorimotor cortex; SCORAD, SCORing atopic dermatitis scale; SPL, Superior parietal lobule; VAS, visual analog scale; aMCC, anterior mid-cingulate cortex; dlPFC, dorsolateral prefrontal cortex; fMRI, functional magnetic resonance imaging; fcMRI, functional connectivity magnetic resonance imaging; pMCC, posterior mid-cingulate cortex; vlPFC, ventrolateral prefrontal cortex..