FOS and colitis: In order to elucidate the cortical regions that are involved in the processing of visceral nociception during acute colitis, we first compared the Fos expression levels (marker for neuronal activation) in several sensory and associative cortical areas in non-inflamed mice that were given either a noxious (80 mmHg) or non-noxious (20 mm Hg) CRD mechanical stimulation.