 Further, Lau and Rosenthal (2011) survey the empirical evidence pertaining to the difference between higher-order theories and first-order ones. While much is equivocal, and many questions are left unanswered, they point to a pair of studies that support a higher-order account. One is Lau and Passingham (2006), who are able to demonstrate using carefully controlled stimuli that there are circumstances in which people’s subjective reports of visual experience are impaired while their first-order discrimination abilities remain fully intact. They also find that visual consciousness in these conditions is specifically associated with activity in a region of dorsolateral prefrontal cortex. Then in a follow-up study Rounis et al. (2010) find that transcranial magnetic stimulation directed at this region of cortex, thereby disrupting its activity, also has a significant impact on people’s meta-visual awareness, but again without impairing first-order task performance. The degree to which the prefrontal cortex is required for having a conscious state and the view that the prefrontal cortex is the likely site of all higher-order thoughts are also the subject of vigorous continuing debate (Block 1995; Gennaro 2012, chapter nine; Kozuch 2014; Odegaard, Knight, and Lau 2017). 