Trends in Neurosciences
Volume 26, Issue 9, September 2003, Pages 507-513
Journal home page for Trends in Neurosciences

Parsing reward

https://doi.org/10.1016/S0166-2236(03)00233-9Get rights and content

Abstract

Advances in neurobiology permit neuroscientists to manipulate specific brain molecules, neurons and systems. This has lead to major advances in the neuroscience of reward. Here, it is argued that further advances will require equal sophistication in parsing reward into its specific psychological components: (1) learning (including explicit and implicit knowledge produced by associative conditioning and cognitive processes); (2) affect or emotion (implicit ‘liking’ and conscious pleasure) and (3) motivation (implicit incentive salience ‘wanting’ and cognitive incentive goals). The challenge is to identify how different brain circuits mediate different psychological components of reward, and how these components interact.

Section snippets

Learning

Multiple forms of learning are mediated by different brain systems, and a change in any one of them might change rewarded responses 1, 2, 3, 4, 5, 6, 7. Learned responses require knowledge – of some type – about the relationships between stimuli and actions. Knowledge is required for reward prediction, for making anticipatory responses, for guidance by cues, and for goal-directed action. Learning processes can be either associative or cognitive. The products of learning can be declarative

Reward: more than learning

Alternatively, neural manipulations can alter an affective (emotional) or motivational process. Components of emotional and motivational processes have received less attention from neuroscientists than learning, but neurobiological studies have now illuminated several distinct components that need to be considered.

First, it is important to note that emotional and motivational components can exist objectively apart from conscious awareness of them. That is, they can occur implicitly. Why posit

Affect (core ‘liking’ and conscious pleasure)

If conscious pleasure is a subjective affective reaction, then what we have called ‘liking’ (in quotes) is an objective affective reaction (Box 1). ‘Liking’ for tastes involves activity in a distributed neural network that also has been implicated in drug reward. One neural component of ‘liking’ involves opioid neurotransmission onto GABAergic spiny neurons in the nucleus accumbens (especially in the shell region). Microinjection of opioid agonists into the accumbens shell causes increased

Motivation [incentive salience (‘wanting’) and cognitive wanting]

If the word wanting generally refers to a conscious or subjective desire, then the term ‘wanting’ (in quotes) can be used as a short-hand phrase to refer to an underlying implicit and objective motivation process: incentive salience. Rewards that are ‘liked’ are usually also ‘wanted’. Indeed, most traditional formulations of incentive motivation viewed ‘wanting’ and ‘liking’ to be so causally connected that they were considered effectively identical – two words for the same process. But

Interactions among wanting, learning and liking

Distributed and interconnected brain circuits allow learning, ‘wanting’ and ‘liking’ to interact in particular ways. Here are highlighted a few important interactions among these components of reward, and details of how to recognize them.

Neuroscience of reward: which component?

In closing, consider again the knockout mouse with distorted cocaine reward. Clearly, it is not enough to say that reward has changed without also asking which specific component of reward. Is there a change in learning? If so, in which form of learning (e.g. Pavlovian associations or cognitive expectancies)? Is there a change in emotional, affective and hedonic reactions to reward? If so, in which form of affect (e.g. immediate ‘liking’ reaction or cognitive representations of hedonic

Acknowledgements

Our work has been supported by grants from NIDA, NIMH, and NSF. We thank Susana Peciña for assistance in preparation of the manuscript and Fig. 2.

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