Disturbed Interhemispheric Functional Connectivity Rather than Structural Connectivity in Irritable Bowel Syndrome

Abstract

Neuroimaging studies have demonstrated that irritable bowel syndrome (IBS)—a relapsing functional bowel disorder—presents with disrupted brain connections. However, little is known about the alterations of interhemispheric functional connectivity and underlying structural connectivity in IBS. This study combined resting-state functional magnetic resonance imaging (rs-fMRI) and diffusion tensor imaging (DTI) to investigate changes in interhemispheric coordination in IBS patients. Resting-state functional and structural magnetic resonance images were acquired from 65 IBS patients and 67 healthy controls (HCs; matched for age, sex and educational level). Interhemispheric voxel-mirrored homotopic connectivity (VMHC) was calculated and compared between groups. Homotopic regions showing abnormal VMHC in patients were targeted as regions of interest (ROIs) for analysis of DTI tractography. The fractional anisotropy (FA), fiber number and fiber length were compared between groups. Statistical analysis was also performed by including anxiety and depression as covariates to evaluate their effect. A Pearson correlation analysis between abnormal interhemispheric connectivity and clinical indices of IBS patients was performed. Compared to HCs, IBS patients had higher interhemispheric functional connectivity between bilateral thalami, cuneus, posterior cingulate cortices (PCC), lingual gyri and inferior occipital/cerebellum lobes, as well as lower interhemispheric functional connectivity between bilateral ventral anterior cingulate cortices (vACC) and inferior parietal lobules (IPL). The inclusion of anxiety and depression as covariates abolished VMHC difference in vACC. Microstructural features of white matter tracts connecting functionally abnormal regions did not reveal any differences between the groups. VMHC values in vACC negatively correlated with the quality of life (QOL) scores of patients. In conclusion, this study provides preliminary evidence of the disrupted functional coordination rather than anatomic coordination between interhemispheric regions within the cortex-thalamus circuit in IBS patients, which could partly account for the enhanced visceral information processing and impaired endogenous pain or emotion inhibition associated with IBS.

Microstructural White Matter Abnormalities in the Dorsal Cingulum of Adolescents with IBS

“…Although our study findings point to decreased FA in the right dorsal cingulum in young IBS patients compared to matched healthy controls, the pathogenesis underlying these WM changes cannot be discerned from the present data. WM abnormalities in FA and other non-FA metrics in the cingulum have been linked to anxiety disorders such generalized anxiety disorder, obsessive-compulsive disorder and post-traumatic stress disorder ( Lochner et al, 2012 ; Daniels et al, 2013 ; Wang et al, 2016 ), as well a various pain conditions, including complex regional pain syndrome (CRPS), temporomandibular disorder, chronic musculoskeletal pain, trigeminal neuralgia, and IBS ( Geha et al, 2008 ; Chen et al, 2011 ; Moayedi et al, 2012 ; Ellingson et al, 2013 ; DeSouza et al, 2014 ; Lieberman et al, 2014 ; Qi et al, 2016 ). Therefore, it is possible that the observed microstructural WM changes reflect sensitization of viscerosomatic nociceptive afferents, leading to functional reorganization in spinothalamic and corticolimbic tracts involved in processing pain and affect, including the dorsal cingulum bundle.…”

Functional network connectivity changes in children with attention‐deficit hyperactivity disorder: A resting‐state fMRI study

“…Thus, brain regions with high intensity show high VMHC values. VMHC can quantize FC between every voxel in two hemispheres and has been applied more and more extensively in the area of pathergasiology (Liang et al, 2017; Qi et al, 2016).…”

The Functional Network Processing Acute Electrical Itch Stimuli in Humans

“…In addition to the SII, functional coupling was also observed between the pIns in the right hemisphere and BG and aIns in the opposite hemisphere. Activity of the BG and insula is strongly synchronized between the hemispheres through the anterior commissure and/or corpus callosum (O’Reilly et al, 2013; Sun et al, 2015; Qi et al, 2016; Su et al, 2016). This may explain why the pIns increased functional connectivity with the BG and aIns not only in the same hemisphere but also opposite hemisphere.…”

“…However, though it did not reach our cluster size threshold, two regions in the right BG showed that intensity of functional connectivity with the right pIns had negative correlation with itch NRS (at least significant for intensity threshold for both regions). Considering strong interhemispheric connectivity of the BG (O’Reilly et al, 2013; Qi et al, 2016), functional network composed of the pIns and bilateral BG may play an important role in regulation of subjective itch sensation.…”