Intrinsic brain abnormalities in irritable bowel syndrome and effect of anxiety and depression

This resting-state functional magnetic resonance imaging (rs-fMRI) study investigated intrinsic brain abnormalities in irritable bowel syndrome (IBS) and effect of anxiety and depression. Thirty IBS patients and 31 matched healthy controls underwent rs-fMRI scanning. Regional brain activity was evaluated by measuring the amplitude of low-frequency fluctuation (ALFF) and compared between IBS patients and healthy controls with a two-sample t-test. Areas with abnormal ALFF were further used as seeds in subsequent inter-regional functional connectivity (FC) analysis. Statistical analyses were also performed by including anxiety and depression as covariates to evaluate their effect. Compared to healthy controls, IBS patients showed decreased ALFF in several core default mode network regions (medial prefrontal cortex [MPFC], posterior cingulate cortex [PCC], bilateral inferior parietal cortices [IPC]), and in middle frontal cortex, right orbital part of the superior frontal gyrus (ORBsup), dorsal anterior cingulate cortex (dACC), and ventral anterior cingulated cortex (vACC), while they showed increased ALFF in bilateral posterior insula and cuneus. In addition, IBS patients revealed decreased inter-regional positive FC between MPFC and right ORBsup, between vACC and PCC, as well as decreased negative FC between MPFC and left posterior insula, while they showed increased negative FC between MPFC and cuneus. The inclusion of anxiety and depression as covariates abolished ALFF differences in dACC and vACC, but none of the FC differences. In conclusion: IBS patients had disturbed intrinsic brain function. High levels of anxiety and depression in IBS patients could account for their decreased intrinsic brain activity in regions (the ACC) involved in affective processing.