Brain imaging approaches to the study of functional GI disorders: A Rome Working Team Report

Abstract

Progresses in the understanding of human brain‐gut interactions in health and disease have been limited by the lack of non‐invasive techniques to study brain activity. The advent of neuroimaging techniques has made it possible not only to study the structure and function of the brain, but also to characterize signaling system underlying brain function. This article gives a brief overview of relevant functional neuroanatomy, and of the most commonly used brain imaging techniques. It summarizes published functional brain imaging studies using acute visceral stimulation of the oesophagus, stomach and colon in healthy control subjects and patients with functional GI disorders, and briefly discusses pertinent findings from these studies. The article concludes with a critical assessment of published studies, and with recommendations for improved study paradigms and analysis strategies.

A sustained hypothalamic–pituitary–adrenal axis response to acute psychosocial stress in irritable bowel syndrome

“…The role of these brain regions in mediating the HPA axis response to acute psychosocial stress in IBS requires further investigation at a functional brain imaging level. However, it is well established that altered central processing of visceral pain plays a key role in IBS (Mayer et al 2009), and we have recently provided evidence that IBS is associated with a deficit in hippocampal-mediated cognitive function (Kennedy et al 2013). Thus, when considering our results along with previous pharmacological challenge tests (Dinan et al 2006) and a recent study describing elevated cortisol levels in anticipation of a public-speaking task (Heitkemper et al 2012), it is likely that HPA axis dysfunction in IBS is best characterized as an exaggerated response, or sustained activation following acute stress, which may, in part, be mediated by altered central processing of the stressful environment.…”

Abnormal Amygdala Resting-State Functional Connectivity in Irritable Bowel Syndrome

“…9 The insula is involved in emotional arousal and visceral sensory, autonomic visceral motor, and pain processing 33 and is consistently activated in healthy subjects exposed to visceral stimuli. 6 The insula is also an essential node in the homeostatic afferent network that is hyperactivated in IBS. 8,16,34 Increased insula activities in patients with IBS during rectal distension 35 and in response to cutaneous heat stimuli 36 have been reported.…”

“…3 With its high prevalence (observed in up to 20% of the population) 4 and the recurrent nature of the symptoms, IBS negatively affects the quality of life of individuals with this condition and is a health care burden for society 5 ; however, the neural basis for IBS has not been examined in detail, to our knowledge. Functional neuroimaging is the only means of identifying the human brain circuitry that is correlated with various phenotypic and behavioral manifestations of functional gastrointestinal disorders, including IBS 6 ; convergent neuroimaging studies have implicated an abnormal emotional arousal network that encompasses emotional, cognitive, and psychological aspects. 7 Hyperactivity of the amygdala within this network is a striking feature of IBS, which has been documented in many studies by using visceral or somatic stimuli.…”

“…7 Hyperactivity of the amygdala within this network is a striking feature of IBS, which has been documented in many studies by using visceral or somatic stimuli. 6,8 The amygdala networks are important in emotional regulation, modulation of sensory information, and processing of visceral information in relation to emotional stimuli. 9 On the basis of the importance of the amygdala in emotional systems and its implication in IBS, this study focused on examining amygdala functional connectivity in patients with IBS.…”

“…Resting-state functional MR imaging is a fairly new approach, which could resolve this issue 10 by measuring spontaneous blood oxygen level-dependent fluctuations in the brain during rest, 11 which has been used in the study of IBS. 6,12 Resting-state functional connectivity (RSFC)-the quantification method most frequently used in resting-state functional MR imaging studies 10,13 -measures interregional temporal correlation between a predefined seed region and functionally related regions 14 and has been used as a reliable and sensitive index in studies of healthy subjects and patients with various brain disorders such as Alzheimer disease, depression, and attention deficit/hyperactivity disorder. 11,15 However, there have been no prior studies using RSFC to investigate the amygdala functional connectivity in patients with IBS.…”