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.
Highlights
Irritable bowel syndrome (IBS), a common functional gastrointestinal disorder with an estimated worldwide prevalence of 10%–20% (Longstreth and Wolde-Tsadik, 1993), is characterized by chronically recurring abdominal pain or discomfort and altered bowel habits (Mayer, 2008; Chey et al, 2015)
All patients were recruited from the Digestive Disease Clinic of our hospital and were clinically diagnosed with irritable bowel syndrome (IBS) by a gastroenterologist with expertise in functional gastrointestinal disorders based on the Rome III criteria (Drossman, 2006) and the healthy controls were collected from the local communities
Scores for MMSE (>26) and MoCA (≥26) for all subjects were in the normal range, while lower MMSE and higher anxiety and depression symptom scores were observed in IBS patients relative to healthy controls (HCs) (P < 0.05; Table 1)
Summary
Irritable bowel syndrome (IBS), a common functional gastrointestinal disorder with an estimated worldwide prevalence of 10%–20% (Longstreth and Wolde-Tsadik, 1993), is characterized by chronically recurring abdominal pain or discomfort and altered bowel habits (Mayer, 2008; Chey et al, 2015). In the absence of detectable organic causes, IBS is referred to as a functional disorder, thought to result from a dysregulation of the brain-gut interaction (Mayer and Tillisch, 2011; Koloski et al, 2012; Weaver et al, 2016). Functional neuroimaging (resting-state and task response) allows for the quantification of the viscerosensory inputs that reach the brain, together with structural and diffusion tensor imaging (DTI), multimodal brain imaging makes it possible to identify the human brain circuitry that is correlated with various phenotypic and behavioral manifestations of functional gastrointestinal disorders including IBS (Mayer et al, 2009). Little is known about the interhemispheric functional synchronization and its associated anatomic connectivity in IBS
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