Forebrain mechanisms of dreaming are activated from a variety of sources

The central question facing sleep and dream science today seems to be: What is the physiological basis of the subset of NREM dreams that are qualitati vely indistinguishable front REM dreams ("apex dreams")? Two competing answ ers have emerged: (1) all ape. dreams are generated by RENT sleep control m echanisms, albeit sometimes covertly; and (2) all such dreams tine generate d by forebrain mechanisms, independently of classical pontine sleep-cycle c ontrol mechanisms. The principal objection to the first answer is that it l acks evidential support. The principal objection to the second answer (whic h is articulated in my target article) is that it takes inadequate account of interactions that surely exist between the putative forebrain mechanisms and the well established brainstem mechanisms of conscious state control. My main response to this objection (elaborated below) is that it conflates nonspecific brainstem modulation - which supports consciousness in general with a specific pontine mechanism that is supposed to generate apes dreamin g in particular. The latter mechanism is in fact neither necessary nor suff icient for apex dreaming. The putative forebrain mechanisms, by contrast, a rc, necessary for apex dreaming (although they are nor sufficient, in the l imited sense that all conscious states of the forebrain are modulated by th e brainstem).