Dopamine-Opiate Modulations of Reward-Seeking Behavior: Implications for the Functional Assessment of Prefrontal Development

Abstract

Much of human behavior is organized around stimuli that we conceptualize as worthy of approach (e.g., positive reinforcers) or emotional attachment (natural rewards). Two separable emotional systems have been described that contribute to these reward-related processes. One of these is a system involved in approach to distal rewards, and the other mediates consummatory aspects of reward acquisition. In addition to their emotional functions, each of these systems is proposed to guide specific cognitive processes. Spatial working memory is viewed as the cognitive extension of an emotional system underlying anticipatory reward and approach to incentive stimuli. Both aspects of behavior share a common neurobiological substrate in the functioning of ascending brain dopamine systems. In contrast, the type of affective state that accompanies reward acquisition is consummatory in nature and serves to keep the organism close to objects and places of attachment. When this system is activated, behaviors promoted by the approach system, including spatial working memory, are inhibited. The consummatory system is mediated, at least in part, by endogenous opiates. In this chapter, the implications of a DA-based incentive system and an opiate-based consummatory attachment system are discussed in relation to the developmental assessment of spatial working memory skills as exemplified by Piaget’s A-not-B task. Specifically, it is proposed that young infants are predominantly guided by an opiate-based attachment system, leading to the A-not-B error and conditioned place preferences when they perform spatial memory tasks. Hence, the resolution of the A-not-B error may represent an affective, rather than a cognitive, milestone reflecting increasing maturity of brain dopamine systems underlying agency and approach to positive stimuli.