Fig. 1.

Naturalistic behavior assays of reward liking and negative fearful defense. Liking facial expressions are elicited by the taste of sucrose from newborn human infants, orangutans, and rats [top left, facial photographs fromSteiner et al. (2001) and Berridge (2000)]. Disliking expressions are elicited by the taste of quinine. NAc coronal map of opioid liking and wanting sites for food reward shows intensity of food wanting produced by morphine microinjections in the shell [bottom left, Peciña and Berridge (2000)]. Accompanying graph shows the increase in sucrose liking reactions caused by morphine microinjections in the accumbens shell. Conversely, anxiogenic and psychotic effects of addictive drugs may be related to natural fearful active defense reactions (right). Fearful defensive treading is elicited naturally from rodents by rattlesnake predators and centrally by GABA agonist microinjections in the caudal accumbens shell [California ground squirrel photograph by John Cooke from Coss and Owings (1989); rat photograph from Reynolds and Berridge (2001)]. Bar graph shows elicitation of fearful defensive treading along a rostrocaudal gradient in the NAc shell after GABA agonist microinjections (Reynolds and Berridge, 2001). Separate mesocorticolimbic channels for appetitive and aversive motivational functions is suggested by sagittal map of NAc shell rostrocaudal segregation of GABA-elicited positive feeding behavior (anteriorx symbols) versus fearful defensive behavior (posterior squares).