Thirst, though, represents only one side of maintaining homeostasis. It’s the other side of thirst. Gracheva, a neurophysiologist at the Yale School of Medicine, studies these rodents, native to North American grasslands, to understand how specific brain regions control thirst. Elena Gracheva (left) has traced how the brains of thirteen-lined ground squirrels (right) suppress their thirst response during many months of hibernation. “The circuit for vasopressin was normal, but thirst neurons were downregulated,” Gracheva said.