but also many other emotional and cognitive aspects. Impaired satiety and reward
control systems can lead to overconsumption, particularly of more palatable,
energy-dense foods (Berridge et al. 2010 ; Castro and Berridge 2014 ; Kenney 2013 ).
The neurological basis of food sensory pleasure is a topic of increasing interest in
neuroscience and psychology. Functional imaging techniques (e.g., fMRI, PET) have
aided the discovery of localized hedonic hot spots (opioid/endocannabinoid/orexin
signals) in the brain. These amplify pleasurable reactions to palatable tastes (i.e.,
liking) in response to particular neurochemical or neurobiological stimulation (e.g.,
sweet taste). The liking mechanisms, responding to unconditioned stimuli (UCS),
include the hedonic circuits that connect hot spots in the forebrain limbic structures,
the nucleus accumbens, ventral pallidum, and brainstem parabrachial nucleus. The
subcortical primary mechanisms in liking can also produce conscious pleasure by
recruiting cortical brain circuits (Berridge et al. 2010 ; Castro and Berridge 2014 ) (see
Fig.10.3). In contrast, wanting refers to motivation triggered by reward-related cues,
conditioned stimuli (CS), like seeing food or images of food. Wanting is influenced by
liking and learning. Wanting can continue to be activated even when foods become
less likable or unpleasant. The wanting mechanisms include the more encompassing
mesocorticolimbic system or larger opioid networks: the nucleus accumbens, striatum,
and amygdala, as well as the mesolimbic dopamine systems (Fig.10.4)(Berridge
et al. 2010 ; Castro and Berridge 2014 ).
Neurologically, wanting and liking are GO systems and never generate strong
STOP signals even in the presence of sensory-specific satiety (Berridge et al. 2010 ;
Castro and Berridge 2014 ). For example, sweet desserts remain appealing even
after a large meal. In one experiment, PET images showed that, when subjects
consumed chocolate to the extent that they experienced sensory-specific satiety and
eating chocolate was no longer pleasurable, activation switched from the medial
Fig. 10.3 Model of incentive motivation separating wanting (incentive salience) from liking
(hedonic impact of sensory pleasures) (Berridge et al. 2010 )
10 Objective and Subjective Aspects of the Drive to Eat in... 213