Animals and humans have the hormone ghrelin in their stomachs. Ghrelin tells animals as well as humans when they are hungry and helps regulate their metabolism, but scientists have never been certain how exactly it works.

To learn more about how ghrelin influences hunger, metabolism and memory, researchers at the USC Dornsife College of Letters, Arts and Sciences collaborated with international scientists on a study of rats. They disrupted the ability of the ghrelin hormone to communicate to the vagus nerve, a nerve that signals from the gut to the brain, and then monitored the impact on their feeding and cognitive behaviors.

The rats were not anxious but they began eating more frequently, said the study’s lead and corresponding author Scott Kanoski, an associate professor of biological sciences at USC Dornsife.

“We think that the increased eating frequency is related to their memory impairment. Memory from when you last ate will influence how soon you eat again. It led the rats in our study to eat sooner.”