The Interdisciplinary Science of Consumption by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 978-0-262-02767-0
Publisher: The MIT Press
Published: 2014-04-14T16:00:00+00:00

Neurobiological Perspectives

9

Appetite, Consumption, and Choice in the Human Brain

Brian Knutson and Uma Karmarkar

According to the Tibetan Buddhist bhavacakra (wheel of life), people who have lived less-than-exemplary lives are reborn in lower realms. Those unfortunate enough to be sent to the realm of pretas (hungry ghosts) awaken as ravenous beings whose tiny mouths and necks block sustenance from entering their large but empty stomachs. The hungry ghosts thus continually suffer from insatiable appetites (Gyatso 1992). This seemingly exotic fate of the hungry ghosts symbolizes a more common earthly state of affairs: when appetite cannot be sated with consumption, as in the case of addiction, the rhythm of life is permanently disrupted. Without the eventual calming effects of consumption, excessive appetites may drive organisms to ruin. The plight of the hungry ghosts implies that appetite and consumption are different but must eventually connect.

From the perspective of neuroscience, this mythical dilemma raises a number of questions. Can different phases of reward processing be distinguished neurally? How do they interact? Can their coordinated function contribute to optimal choice and well-being? In this chapter, we attempt to define appetite and consumption psychologically, and then to describe human neuroimaging research indicating that these phases of reward processing can be visualized in the human brain. We then survey emerging research suggesting that neural study of these processes may help scientists to better predict choice and understand processes that promote decision making.

Definitions

More than 100 years ago, the ethologist Wallace Craig defined appetitive and consummatory behavior as follows (Craig 1918): “An appetite . . . is a state of agitation which continues so long as a certain stimulus . . . is absent. When the appeted stimulus is at length received it stimulates a consummatory reaction, after which the appetitive behavior ceases and is succeeded by a state of relative rest.” Craig’s prescient definition has a number of implications. First, the cycle of appetite and consumption has distinct behavioral components that occur sequentially. Second, although both appetite and consumption evoke arousal, appetite involves higher arousal than consumption. Third, consumption forms a negative feedback loop that can eventually reduce appetite. Fourth, although the terms appetitive behavior and consummatory behavior may have originally referred to eating episodes, they can also extend to a broader range of activities (see the chapter by Plassmann and Wager, the chapter by Preston, Kringelbach, and Knutson, the chapter by Preston and Vickers, the chapter by Kringelbach, and the chapter by Robinson, Robinson, and Berridge).

As with most scientifically useful definitions, Craig also clarified what appetitive and consummatory behavior are not. He argued that appetitive and consummatory behaviors were driven by positive motivation, but not by negative motivation (associated with avoidance behavior). He also specified that appetitive and consummatory behaviors were not reflexive (as might be assumed by later behaviorists), nor were they strictly yoked to goals (as might be assumed by later cognitive theorists). In this chapter, we use Craig’s ethological definition as a starting point. We further assume that,

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