CZ:Featured article/Current

Food reward

Food intake involves both 'homeostatic feeding' (energy demands) and ‘non-homeostatic feeding’; the latter is associated with food reward, which involves both 'liking’ (pleasure/palatability) and ‘wanting’ (incentive motivation) according to the salience theory. Experiments in mice suggest that ‘liking’ involves the release of mu-opioid peptides in brain, while ‘wanting’ involves the neurotransmitter dopamine ^[1].

Motivated behaviour and food as a reinforcer

The brain’s reward systems react to stimuli such as sight, smell and taste, and other cues that predict food. However, hunger cannot result in unconditioned goal-directed behaviour; ^[2] chance encounters with palatable foods are required before goal-directed behaviour can occur, which link the internal needs with the salience of environmental stimuli ^[3]For exa mple, an infant recognises and learns to seek out sweet tastes, but the desire for any particular food is controlled by the interaction of peptide levels (related to hunger) with neural circuits in the brain which store the animal’s past experience of that particular food. ^[4] Subsequently, the infant will taste both food and non-food objects indiscriminately until it has received reinforcing feedback from enough stimuli. A monkey’s appetite for yellow bananas requires that the monkey learns to relate the sight of the yellow skin of a banana with the sweet taste of the banana, plus the consequences of eating it. Preference for a particular food results only when the post-ingestional consequences of that food ’reinforce’ the tendency to eat that food. For these reasons, food is considered to be a strong reinforcer. When the response of a behaviour stimulated by a reinforcer increases the frequency of that behaviour; that is positive reinforcement or reward learning, and the positive events are called rewards ^[5]. The reinforcing efficacy of food reward is the ability of the reward to maintain rather than to establish behaviour; consequently the stimulus learning contributes to the response learning.

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notes
↑ Berridge KC (2007) The debate over dopamine’s role in reward: the case for incentive salience. Psychopharmacology 191:391–431 ↑ Changizi MA et al. (2002) Evidence that appetitive responses for dehydration and food-deprivation are learned Physiol Behav 75:295–304 ↑ Wise RA (2006) Role of brain dopamine in food reward and reinforcement Phil Trans R Soc Lond B Biol Sci 361:1149–58 ↑ Steiner JE et al.(2001) Comparative expression of hedonic impact: affective reactions to taste by human infants and other primates Neurosci Biobehav Rev 25:53–74 ↑ Epstein LH et al.(2007) Food reinforcement and eating: a multilevel analysis Psychol Bull 133:884–906

[1] Berridge KC (2007) The debate over dopamine’s role in reward: the case for incentive salience. Psychopharmacology 191:391–431

[2] Changizi MA et al. (2002) Evidence that appetitive responses for dehydration and food-deprivation are learned Physiol Behav 75:295–304

[3] Wise RA (2006) Role of brain dopamine in food reward and reinforcement Phil Trans R Soc Lond B Biol Sci 361:1149–58

[4] Steiner JE et al.(2001) Comparative expression of hedonic impact: affective reactions to taste by human infants and other primates Neurosci Biobehav Rev 25:53–74

[5] Epstein LH et al.(2007) Food reinforcement and eating: a multilevel analysis Psychol Bull 133:884–906

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CZ:Featured article/Current

Food reward

Motivated behaviour and food as a reinforcer

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