Orbitofrontal cortex, in particular, plays a central role in the coding of reward (e.g., Breiter et al., 1997; Kringelbach et al., 2003; O’Doherty et al., 2001), with its responses varying as a function of satiety. In primates, orbitofrontal neurons that respond to food odors decrease their responses to the odor of a food eaten to satiety (Critchley and Rolls, 1996). In humans, O’Doherty et al. (2000) and Kringelbach et al. (2003) showed that when a particular food is eaten to satiety, the perceived reward value of its odor decreases, as does the activation induced by the odor in orbitofrontal cortex; perceived reward/pleasantness and activation nevertheless remain unchanged to the odor of unconsumed food. Likewise, Gottfried et al. (2003) showed that orbital activation to a conditioned visual stimulus (an abstract design previously paired with a food odor) also varied as a function of satiety in a similar manner, as did activation in the ventral striatum, cingulate cortex, amygdala, and insula.
