Figure 3. ‘Liking’ for sweetness is never enhanced by hypothalamic electrodes or by dopamine elevation.
Turning on stimulation of lateral hypothalamic electrodes in the same rats as in Figure 4 causes more ‘disliking’ reactions (e.g., gapes) to sucrose, while not altering positive ‘liking’ reactions (e.g., lip licks), even though the stimulation made the same rats avidly eat more food. Elevation of dopamine in mutant mice only suppresses positive ‘liking’ reactions to sucrose at the highest concentration (while not altering lower ‘liking’ for dilute sucrose solution; aversive reactions were not observed and are not shown), even though the mutants ‘wanted’ sweet rewards more than control wild-type mice. Modified from Berridge and Valenstein (1991) and from Pecina et al. (2003).