It’s near daybreak. The alarm goes off. You roll over and switch on the light.

What’s going on for you at that moment? The last hint of a dream may be fading – your eyes are adjusting to the sudden glare – and some of your brain’s cells are growing tiny new connective strands.

Does that last one sound like a tidbit from an unusually implausible science fiction story? In fact, there’s a good chance it’s true.

Elly Nedivi, assistant professor of brain and cognitive sciences, explores how different stimuli affect the brain. One of her most provocative findings is that something as simple as exposure to light can touch off structural changes in brain cells.

The first hint of this possibility came from Nedivi’s work with rodents. She exposed some to light and left others in the dark. Then, using gene-testing methods of exquisite sensitivity, she asked the key question: Were any genes turned on in a target region of the light-exposed animals’ brains that weren’t activated in the others’ brains?

“At least six genes were getting turned on,” she says. And some of these proved to be catalysts for the growth of tiny tendrils in brain cells.

Though all her work is with lab animals, Nedivi believes we’d find something similar if we could peer microscopically into the brain of someone in a room where a light had just been switched on.

Does this mean our brains are changing structurally from one end of every waking hour to the next? (And maybe in sleep, too, since our brains experience dreams as stimuli just as they do real-world sights, sounds and smells.) “I think our data strongly support that idea,” she says.

Even scientists are uncomfortable with the notion. When she presents her work at scientific meetings, says Nedivi, “people will come up and say, ‘Does it really have to be that messy?'”

Nedivi emphasizes that many of the changes triggered by, say, switching on a light wouldn’t last. “It’s likely some are being strengthened because they’re active, and others are being eliminated,” she notes.

She also notes that the changes, even when sustained, are tiny. The growing tendrils, called dendrites, are less than a tenth the width of a human hair, and the extent of their growth might be about what one of our fingernails grows in a few hours.

Still, she says, the idea that the brain’s structure changes almost constantly makes sense. “People think of the brain as being like a computer, but it’s not,” she notes. “It’s made out of protein, and connections made out of protein aren’t going to last a lifetime.”