The Effect of Inhibitory Control Processes Induced by Rectal Distension on Impulse Control Measured by Stroop Task Performance and Intertemporal Discounting.

The aim of this study will be to investigate the effect of rectal distension, controlled by electronic barostat, on cognitive control ability in healthy subjects. We will use the Stroop task and an intertemporal choice task as standard instruments. Like bladder control and rectal control, both Stroop task performance and intertemporal choices - though very different tasks at the surface - are dependent on the conflict monitoring function of the anterior cingulate cortex. The Stroop task requires the naming of the print color of a series of visually presented color words, and reaction time and error rates are typically used as performance indicators. When word color and word meaning do not match, performance of the task (color naming) requires the inhibition of a (near) automatic response (word reading). The intertemporal choice task consists of a series of choices between a sooner smaller monetary reward and a larger but later reward. The choices are constructed such that they allow the estimation of a discount parameter, which is an index for the level of impulsiveness manifested by the participant at the time the choices are made. The hypothesis is that the inhibition induced by the urge generated during rectal distension will improve cognitive inhibitory performance, as has previously been shown for bladder filling.