The projection of anorectal afferents to cortex of the rat: Comparison of two methods of cortical mapping

Abstract

Background The rat has served usefully as a model for fecal incontinence and exploration of the mechanism of action of sacral neuromodulation. However, there is a gap in knowledge concerning representation(s) on the primary sensory cortex of this anatomical region. Methods Multi‐electrode array (32 channels) and intrinsic optical signal (IOS) processing were used to map cortical activation sites following anorectal electrical stimulation in the rat. A simple method for expanding a 32‐electrode array to a virtual 2700 array was refined. Key Results The IOS method identified activation of parietal cortex following anorectal or first sacral nerve root (S1) stimulation; however, the signal was poorly localized and large spontaneous vasomotion was observed in pial vessels. In contrast, the resulting high‐density maps showed two anatomically distinct cortical activation sites to anorectal stimulation. Conclusions & Inferences There are two distinct sites of activation on the parietal cortex following anorectal stimulation in the rat. The implications for sacral neuromodulation as a therapy for fecal incontinence are discussed.