Brain research in functional gastrointestinal disorders.

The current understanding is that functional gastrointestinal disorders (FGIDs) result from dysregulation of the bidirectional communication between the gut and the brain (i.e., the brain-gut axis), modulated by various psychosocial and environmental factors (i.e., the biopsychosocial model). This concept has led to a growing interest in the research of brain function in relation to gut motor and sensory function. Brain research on the mechanisms that are involved in the generation of gastrointestinal symptoms includes studies of the gut response to brain stimulation with technique such as transcranial magnetic stimulation or studies of the brain response to gut stimulation by cortical evoked potentials, positron emission tomography, and functional magnetic resonance imaging. Studies using these techniques have shown that visceral/gut sensation involves activation of several brain regions that are associated with various brain functions, including sensation, cognition, and affect. The complexity of the brain response to visceral stimulation and the multidetermined nature of FGIDs make studies of brain function in FGID patients difficult and demands great caution in interpreting their results. Nevertheless, brain research in FGIDs is an emerging field and suggests that patients with irritable bowel syndrome differ from healthy subjects in the way that their brain response to visceral (e.g., rectal) distention. These studies emphasize the role of the central nervous system in conducting and processing visceral signals and suggest that alteration in brain processes involving perception and affective responses might be key factors in the pathogenesis of functional gastrointestinal symptoms.