Reward-specific satiety and reward-specific motivation: neural bases and significance.

How choices are made between rewards is fundamental to understanding the behavior of humans and most other vertebrates. A key factor in the choices is reward-specific satiety, which is the sensory-specific decrease in the reward value of a particular reward when it is consumed to satiety. Another key factor is reward-specific motivation, the increase in the reward value of a reward when it is first provided. Here, we develop the theory based on experimental evidence in humans and other primates, that reward-specific satiety is implemented in orbitofrontal cortex reward value neurons by adaptation in the synapses from visual and taste cortical regions in which the neuronal firing is not influenced by reward-specific satiety. Correspondingly we develop the theory that reward-specific motivation (or incentive motivation) is implemented by shorter-term synaptic facilitation in the same synapses on to orbitofrontal cortex reward value neurons. We complement the theories with an integrate-and-fire neuronal network model of how these reward value computations are performed in the orbitofrontal cortex by synaptic adaptation and synaptic facilitation in the afferent connections to orbitofrontal cortex reward value neurons, to implement a profound influence on behavioral choice that has great adaptive value for humans and many other animals.