This third section of Notes on Dreaming continues Meissner's admirable efforts to integrate neurophysiology with Freud's dream theory. The author

points out that REM activity and dreaming cannot be considered as equivalent; dreaming occurs during NREM periods, and REM activity is seen in decorticate humans who presumably do not dream. REM periods seem to be produced by cyclic physiologic factors; that is, activation of septo-hippocampal circuits. This change in physiologic state sets the stage for changes in cognitive organization so that drive tensions come to serve as organizers of the dream content.