ABSTRACT
Some functional neuroimaging studies have reported a segregation of brain systems that process the affective or hedonic aspects of physical pain and those that process the sensory-discriminatory aspects. This chapter discusses evidence from animal and human studies of the brain circuitry that enables the brain to create pleasure and displeasure. It then reviews how top-down influences such as homeostatic utility, internal motivational state, and surrounding contextual factors interact with sensory signals to shape hedonic value and decisions. The flexibility and constraints of top-down influences on sensation are still being explored, but it is likely that for the perception of most stimuli, the (un)pleasantness is more malleable than non-affective characteristics. Extensive evidence suggests that hedonic events can be functionally and neuroanatomically segregated into (dis)liking, motivational, and learning components. The chapter also discusses what mixed emotions can tell us about the nature of pleasure and displeasure in the brain.
