“There were a whole bunch of interventions we used to make sure that it would really feel strange and different and isolated,” Saxe said. “They had to let us know when they were going to the bathroom so we could make sure it was empty. We delivered food to the door and then texted them when it was there so they could go get it. They really were not allowed to see people.”
On a different day, each participant underwent 10 hours of fasting. After the 10-hour period of isolation or fasting, the participants were scanned in an MRI machine while looking at images of food, images of people interacting and neutral images such as flowers.
The researchers focused on the substantia nigra, a tiny structure in the midbrain that has been linked with hunger cravings and drug cravings.
The researchers found that when socially isolated subjects saw photos of people enjoying social interactions, the “craving signal” in their substantia nigra was similar to the signal produced when they saw pictures of food after fasting.
The researchers also found a participant’s normal level of social interaction affected their craving after isolation. “For people who reported that their lives were really full of satisfying social interactions, this intervention had a bigger effect on their brains and on their self-reports,” Saxe said.
Now that the researchers can observe the effects of social isolation on brain activity, Saxe said they can try to answer additional questions, such as how social isolation affect people’s behavior, whether virtual social contacts such as video calls help to alleviate cravings for social interaction and how isolation affects different age groups.