Reward Neurophysiology and Orbitofrontal Cortex

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The (primate and human) orbitofrontal cortex receives taste, olfactory, visual, somatosensory, and auditory inputs from cortical regions which are toward the end of the unimodal cortical processing streams that build representations of what stimulus is present in each of these sensory modalities. Neurophysiological studies in primates show that it is the reward value of taste, olfactory, oral texture, and visual stimuli that is represented, as shown, for example, by the reduction to zero of the neuronal responses after feeding to satiety on a particular food. The reward is partly specific to a particular food, as shown by sensory-specific satiety-related neuronal responses. Visual and olfactory stimuli become rewarding by learned association with a primary (unlearned) reinforcer such as the taste of food. This learning can be reversed (in as little as one trial for visual stimuli) and may be facilitated by error neurons that respond when an expected reward is not obtained. Complementary neuroimaging studies in humans show that abstract reinforcers such as monetary reward are also represented in the orbitofrontal cortex, and that the expected value of a reward may be represented in the orbitofrontal cortex.