The present investigation was designed to study the role of stress on the physiologic mechanisms of the colon in irritable bowel syndrome (IBS). Patients with IBS were compared with normal controls during resting and stress (mental arithmetic, cold pressor, and fear stressor). The results indicated that IBS patients had significantly higher motor activity than normals in the resting state but did not differ from them in the mean dominant frequency of the basal electrical rhythm (BER) or the proportion of the time they had 2-4 cycles per minute (cpm) slow-wave activity. Stress significantly increased motor activity in both groups although they did not differ significantly from each other during stress. Stress increased the proportion of 2-4 cpm slow-wave activity in IBS patients, but decreased in the controls. The type of stressor, however, did not influence either motor or electrical activity. Although IBS patients were significantly older than the controls and scored higher on the MMPI scales of Hypochondriasis, Hysteria, and Depression, these factors did not significantly influence differences in motor or electrical activity between the groups. The results are discussed in terms of the role of learning in the colon.
There is considerable evidence indicating that patients with irritable bowel syndrome respond to emotional and environmental stimulation with increased colon motor activity. It has been suggested also that increased colon motor activity is not confined to the colon and may be representative of a broader disorder affecting the rest of the gastrointestinal tract in this population. The results of our current study suggest that anger may have a significant, although differential effect on antral motor activity in IBS patients compared to normal controls. We found that while antral motor activity did not differ significantly in our groups during rest, anger decreased antral motor activity in IBS patients and increased antral motor activity in normal controls. The difference was not attributable to a difference in anger levels since the groups did not differ in their response to the standardized anger stressor. Rather, the difference in the antral motor response appears to be qualitative and a possible marker for irritable bowel syndrome. Our data further suggest that increased colon motor activity in IBS patients during emotional stress is not a result of a rise in motor activity throughout the gastrointestinal tract, but a phenomenon that may be unique to the colon in this patient population.
1) None of the four parameters of a conventional anorectal manometry can accurately separate patients with neurogenic incontinence from those with secondary forms of the disorder. 2) The anorectal motility index presented here can accurately separate the two groups. 3) This index is superior to the standard anorectal manometry in evaluating patients with fecal incontinence.
These experiments assessed (a) the Partial Reinforcement Effect (PRE) when extinction was measured by the perseverative behavior following the blocking of a learned maze route and (b) the effects of two conditions of partial extinction on the same perseverative behavior. Initial training of the rat Ss varied in both number of trials and reinforcement schedule. Perseverative behavior was evaluated by recording cumulative errors. The results indicated that the perseverative behavior increased with an increase in the number of training trials. Perseverative behavior was also observed to be greatest following 100% rather than a ratio schedule of reinforcement, a fixed ratio resulting in greater perseveration than a variable ratio. When 10 nonreinforced trials or 10 nonreinforced goal placements followed 100% reinforced training, the perseverative behavior following blocking was reduced. These results indicate that the typical PRE which has been observed (when the extinction series includes the performance of the instrumental act) is dependent on the stimulus cues provided by the change in reinforcement schedule.
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