Maté describes the distress of patients with “functional” conditions, like irritable bowel syndrome (IBS), as well as chronic fatigue syndrome and fibromyalgia, which are not explainable by any anatomical, pathological, or biochemical abnormality or by infection. These patients have no explanation for their pain available from modern medicine and no course for relief of their symptoms. Maté critiques the biomedical model, which leaves no room for patients’ symptoms that are not verifiable by physical examinations or scans. He suggests that the nervous systems of people may differ greatly in their sensitivity to bodily processes, citing a study whereby a balloon was inflated in the bowels of participants. The IBS group (compared to a control group) experienced higher levels of self-reported pain, particularly in stretches of the bowel with gut wall tension (it is normal for stretches of the gut wall to tense and slacken through the process of digestion). In another study using a PET scan (indicating brain region activity), rectal distension caused prefrontal cortex activation in people with IBS but not in a control group, suggesting that the event had emotional significance for people with IBS, likely stress or distress. This suggests physiological hypervigilance in people who have IBS.