Current work on central nervous system (CNS) mechanisms underlying behavior has expanded from consideration of specific sensory codes or motor controls to the analyses of global CNS states. These include states of arousal, alertness, attention, emotional states regarding emotion and motivation, and states of addiction, which carry great importance for medicine and public health. In this brief introduction, orderly neuroanatomical concepts of forebrain pathways regulating motivated behaviors are presented. Neuropeptides often coordinate large sets of responses associated with an individual behavioral state. Here, we emphasize some of the central roles for opioid peptides. We also mention a few outstanding unanswered questions related to this area of neuroscience.