Boston, Mass. — Interoception is the awareness of our physiological states; it’s how animals and humans know they’re hungry or thirsty, and how they know when they’ve had enough to eat or drink. But precisely how the brain estimates the state of the body and reacts to it remains unclear. In a paper published in the journal Neuron, neuroscientists at Beth Israel Deaconess Medical Center (BIDMC) shed new light on the process, demonstrating that a region of the brain called the insular cortex orchestrates how signals from the body are interpreted and acted upon. The work represents the first steps toward understanding the neural basis of interoception, which could in turn allow researchers to address key questions in eating disorders, obesity, drug addiction, and a host of other diseases.

Using a mouse model his lab developed at BIDMC, Mark Andermann, PhD, principal investigator in the Division of Endocrinology, Diabetes and Metabolism at BIDMC and Associate Professor of Medicine at Harvard Medical School, and colleagues recorded the activity of hundreds of individual brain cells in the insular cortex to determine exactly what is happening as hungry animals ate.

The team observed that when mice hadn’t eaten for many hours, the activity pattern of insular cortex neurons reflected current levels of hunger. As the mice ate, this pattern gradually shifted over hours to a new pattern reflecting satiety. When mice were shown a visual cue predicting impending availability of food — akin to a person seeing a food commercial or a restaurant logo — the insular cortex appeared to simulate the future sated state for a few seconds, and then returned to an activity pattern related to hunger. These findings provided direct support for studies in humans that hypothesized that the insular cortex is involved in imagining or predicting how we will feel after eating or drinking.