Imagine a waterfall.
Misty air.
Blue pool. Trees swaying around the edge.
Hear it too?
That deep, rolling roar as the water crashes down.
It sounds real. It feels almost tangible. But it isn’t happening to you right now. You aren’t standing on that wet rock.
So why does it feel like it?
“Why is it that we experience those thoughtS and sensations almost as if we’re perceiving them?”
Neuroscientist Rodrigo Braga wondered that as a teenager.
He’d heard his own inner voice—narrating thoughts, replaying conversations, whispering advice—and it felt bizarrely loud. Distinct.
Real.
Braga still thinks it’s strange. He works at Northwestern University’s Feinbg School of Medicine now, in Chicago. For years, he’s chased that specific feeling of mental presence. The answer, or at least a piece of it, appeared on March 31. His team published new findings in Neuron.
They didn’t ask eight participants to memorize photos or repeat scripts.
That’s not how we use our imaginations in the wild.
Instead, they handed them open-ended prompts.
Imagine a castle on a hill.
Picture a rock song blasting from a radio.
The instructions were vague on purpose. Vague is honest.
An MRI scanner hummed around the eight subjects, recording their brain activity.
Then the team asked them about it.
Was the image clear? Was the sound vivid?
How realistic did the castle’s stones feel? Did you hear the guitar riff?
Mapping the internal movie
The data told a story most of us haven’t felt.
It’s not a simple playback of the eyes and ears.
You don’t imagine by hitting “rewind” on your sensory input.
When participants imagined locations, their brains lit up in default network A.
This is the part of the brain that handles space and real-world navigation.
It didn’t matter that the castle was fictional. The brain treated the space as if it were physical.
When they imagined speech—like that rock song—their language network fired up.
Same spot that activates when you’re reading this sentence out loud. Or listening to someone tell you a secret.
The imaginary sights and sounds borrowed heavily from the brain’s existing hardware.
But there’s a catch.
Or a distinction, maybe.
These areas aren’t strictly visual.
They aren’t purely auditory either.
The study found that high-level networks did the heavy lifting.
Not the parts of the brain that decode raw color, or line edges, or raw sound waves.
Nathan Anderson, a neuroscientist at Brigham Young University who worked on the study, points out why.
Visual cortex deals with fine detail. Edges. Colors.
When you picture a generic castle, do you imagine every brick’s texture? Probably not.
So those detailed processors stay quiet.
They aren’t needed.
“People don’t necessarily imagine fine details… so the neurons that handle specific visual details are not needed.”
Stephen Kosslyn, a neuroscientist at Harvard who didn’t join the team, agrees.
If you ask someone to picture the exact object they just saw, yeah, the vision areas wake up.
But for general scenes? Those lower-level centers can take a nap.
Alfredo Spagna, a psychologist in Rome, says this vagueness is actually a feature, not a bug.
Real life isn’t a high-resolution photo dump.
It’s impressions. Concepts. A castle. A song.
Most of our day-to-day mental imagery matches that low-detail, high-level structure.
The brain doesn’t rebuild the scene pixel by pixel.
It constructs the idea of it.
So we can visualize spaces.
We can rehearse sentences.
The feeling is vivid because the networks handling spatial reality and language are engaged fully.
Just not the sensors that gather raw data from the world.
Braga wanted to know why thoughts feel like perceptions.
This study suggests it’s because we borrow the brain’s interpretation centers.
Not its intake valves.
There’s a difference, isn’t there?
Still.
A castle on a hill.
It’s solid enough to lean on in the mind’s eye.
Spagna thinks we’re just getting started.
This paper breaks down one small part of that murky, difficult concept of “vividness.”
There’s still so much we don’t know about how we conjure things that aren’t there.
How much of reality is just convincing enough to trick the mind?
