Adjusting to a shifting reality

Alex Eben Meyer

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How do we learn? How do we make sense of the changing world? These are the elemental questions that George Dragoi is trying to answer. An associate professor of psychiatry and neuroscience at the School of Medicine, Dragoi explores how brains construct reality, and how they adjust when that reality shifts.

In a study published in Nature Communications, Dragoi and his colleagues have delineated precisely how the brain adapts when navigating an altered route. The researchers found that key parts of the brain switch rapidly between accessing existing mental maps and analyzing the new environment. Dragoi says this “mental flickering,” as he calls it, may be a fundamental characteristic of how we learn.

“There’s this cycling between what we already know and what we are experiencing now, this bouncing back and forth between those two things,” he says.

The researchers studied rats as they found their way through a maze to a food reward. Once the rats had mastered the maze, the scientists changed the configuration, forcing the rats to identify a new route. During the process, the researchers measured activity in the rats’ hippocampi, the brain region that plays a central role in learning and memory. They found that particular neurons fired in a specific, repeatable sequence, indicating the rats’ brains were making use of preexisting cognitive maps. When the new route was introduced, they alternated.

The researchers argue that this back-and-forth indicates that the rats’ brains were trying to integrate the unfamiliar terrain into the prior cognitive map. 

Scientists had previously known about these memory-related firing sequences. But Dragoi and his team went further, showing for the first time exactly how the existing pattern alternated with the new one when the situation shifted. In Dragoi’s view, this dynamic interplay, between past knowledge and present reality, may be central to how we learn.  “When you speak, you pull words from your existing vocabulary,” says Dragoi, “but you don’t aways say the same thing.”