Biofeedback therapy improves bowel symptoms and anorectal function in patients with dyssynergic defecation, however its mechanism of action is not known. The investigators hypothesize that biofeedback therapy enhances gut-brain-gut communication by altering cortical processing of information and improving cortically mediated neuromuscular function of the gut. The investigators' specific aims are; (1) To evaluate the afferent cortical evoked potentials in response to the electrical stimulation of the anorectum (i) before and after biofeedback therapy and (ii) compare responders with nonresponders. (2) To evaluate the corticofugal tracts (efferent) by recording the anal and rectal electromyographic responses following noninvasive lumbosacral and transcranial magnetic stimulation (i) before and after biofeedback therapy and (ii) compare responders with nonresponders.