Figure 5. Taste ‘liking’ reactions and detail map of nucleus accumbens hotspot.
Positive ‘liking’ reactions to sweet tastes or aversive ‘disliking’ reactions to bitter tastes are homologous in human newborn, young orangutan, and adult rat (left). Opioid hotspots and coldspots in the nucleus accumbens (medial shell shown in sagittal view; center). Green: the entire medial shell supports opioid-stimulated increases in ‘wanting’ to eat food after microinjections of opioid agonist DAMGO. Red: only a cubic-millimeter sized hedonic hotspot also generates increases in ‘liking’ for sweetness. Blue: in a small hedonic ‘coldspot’ opioid stimulation suppresses ‘liking’ reactions to sucrose, and in a larger purple zone suppresses ‘disliking’ reactions to quinine, all while still stimulating intake. Fluorescent Fos plume to DAMGO microinjection (right). Reprinted by permission from (Smith et al., 2010), based on data from (Peciña and Berridge, 2005).