In addition to the role of water in evoking a swallowing reflex, the perceptual consequences of water taste may play a critical role in regulating fluid intake (thirst) and the maintenance of hydration. The responses described here were recorded with passive stimulus delivery in a non-deprived state and in the absence of post-ingestional effects. It is possible, however, that homeostatic variables such as thirst may modulate the responses to water. For example, in an imaging study of thirst and water taste processing in the human gustatory cortex, the primary gustatory cortex (anterior insula and frontal operculum) was activated by water regardless of thirst but the secondary gustatory cortex (caudal orbitofrontal cortex) only showed water-evoked activation in a water-deprived state (de Araujo et al., 2003). The most likely source of this water-selective cortical activation is taste-related structures that receive input from the oropharyngeal area. The ability of cortical neurons to distinguish between water and other tastes supports the idea that water may be processed as an independent taste quality.