When thirsty mice receive cues that water is available, electrical patterns are unleashed throughout their brains, leading the animals to seek and consume water.
Liqun Luo and Karl Deisseroth at Stanford University in California and their colleagues recorded neural activity in mice as they drank water. On each run of the experiment, the team exposed mice to one of two odours: one indicated that licking a spout would produce water; the other indicated that licking the spout would yield nothing.
In thirsty animals, the odour that signalled water availability triggered a wave of neural activity that spread through all 34 brain regions that the team monitored. This activity persisted until just after the animals drank. In animals that were not thirsty, however, an initial wave occurred but tapered off quickly, and the animals did not try to drink.
The researchers then took sated mice and artificially activated neurons known to sense thirst. This restored brain-wide activity to the ‘thirsty state’ and induced water-seeking behaviour in these animals.
The results help to explain how neural signals for thirst control the transformation of sensory cues about water availability into goal-directed behaviours such as drinking.