It is generally accepted that the mammalian pain system has both a sensory and an affective pathway, and that these can be dissociated to some degree both pharmacologically (with morphine, e.g.) and surgical lesions.  The anterior cingulate cortex (ACC) is a particularly important structure of the mammalian brain in this regard (Price 2000).  Allen et al. (2005) and Shriver (2006) argue that this dissociability provides a route to empirical assessment of the affective component of animal consciousness, and Farah (2008) uses it to distinguish suffering from “mere pain”.