By using sophisticated imaging techniques that allow us to visualize the activity of the living human brain (see “Looking Into the Living Human Brain”), researchers at the UCLA Neuroenteric Disease Section have recently identified for the first time the regions within the brain that are involved in the perception and modulation of visceral sensations, including visceral pain. In addition, by comparing brain responses to an acute intestinal stimulus between healthy control subjects, patients suffering from IBS, and patients with ulcerative colitis, they were able to identify specific alterations in how the brains of IBS patients process and respond to acute colonic pain. These research results have recently been published in Gastroenterology. This is the first study which has been able to identify an objective biological marker that is only seen in IBS patients and that is located within brain regions, which are likely to be involved in the alterations in perception and autonomic responses that underlie the most common IBS symptoms. These findings are the first step in a better understanding of how these symptoms develop and how we can treat them by identifying specific targets for pharmacological therapy.

The most prominent brain region found to be activated in response to intestinal stimulation in healthy subjects was a specific area within the anterior cingulate cortex which forms part of the limbic system. The limbic system, which has also been referred to as the “visceral cortex” plays a prominent role in a wide range of functions—from maintaining homeostasis, to autonomic control of the digestive system, to pain perception to the generation of feelings and emotions, and to memory of past emotional states. The specific area within the anterior cingulate cortex identified in the brain imaging studies plays a prominent role in several aspects relevant to IBS symptoms: 1. It is the “executive area” in the regulation of colonic motility and water absorption which in turn determines the frequency and consistency of bowel movements. 2. It is part of the medial pain system which determines the affective component (i.e. the degree of suffering or unpleasantness) associated with pain perception. Specific regions with the medial pain system play an important role in suppressing the perception of pain by releasing endorphin molecules (the body’s own painkillers), while other regions participate in the memory formation of past painful experiences. 3. The brain region identified by the UCLA researchers plays a prominent role in the regulation of maternal behaviors and is crucial for mediating communication between newborns and their mother.

The results of this study have wide ranging implications for all patients suffering from IBS. The findings for the first time have established IBS as a biological disorder, which can no longer be labeled psychological or “not real” by the healthcare system. The current results are the basis for future research efforts delineating the networks and receptors within the brain that are responsible for such IBS symptoms as abdominal pain and discomfort, sleep disturbance, and altered bowel habits. A range of brain imaging studies are currently underway at UCLA which aim at unraveling these mechanisms. Brain regions and receptor systems identified by functional brain imaging studies are likely to become targets for new drug developments in the near future.

For more information about the research efforts by the UCLA Neuroimaging Group, please call (310) 268-3432.