Felipe Fregni, an associate professor at Harvard Medical School who was involved with the research, has a theory on why that happened. “The students ingested fewer calories because they could make more rational decisions,” he says.
He says tDCS may have dialed up the activity in the students’ prefrontal cortices—where the stimulation was applied and where they make rational, considered decisions, which in turn dialed down the students’ initial knee-jerk reaction to eat food when they saw it. This makes good sense: The dorsolateral prefrontal cortex is known to be an area of the brain that enables us to inhibit temptation.
“It’s the part of the brain most developed in humans compared to monkeys, and it relates to some of the more advanced abilities we have,” says Roi Cohen Kadosh, a neuropsychologist at the University of Oxford who is another of the leading lights in tDCS research. “It’s involved in learning and working memory, and it’s highly connected to other brain regions, such as ones involved with addictions and rewards, and food is rewarding.”