A new study finds that looking at something and imagining it triggers the same exact process in the brain. It’s also very similar to the process artificial intelligence uses to create an image.
AILSA CHANG, HOST:
OK, if I say the word puppy, you probably get a mental picture of something cute and cuddly with ears and a wiggly tail. And that’s because most brains can generate an internal image without any input from the eyes. NPR’s Jon Hamilton reports on a study that helps explain our visual imagination.
JON HAMILTON, BYLINE: Scientists know a lot about how our brains make sense of what we see. But Varun Wadia, a researcher at Cedars-Sinai Medical Center and Caltech, wanted to understand a brain function that’s more mysterious.
VARUN WADIA: I can look at an object in the world around me, but I can also close my eyes and imagine the object.
HAMILTON: So Wadia and a team studied the brains of 16 patients with epilepsy. All were in the hospital and already had electrodes in their brain so doctors could find the source of their seizures. That allowed Wadia’s team to monitor the activity of more than 700 individual neurons in each participant as they watched a computer screen.
WADIA: Patients are just looking at a large number of objects that are chosen to sample a large number of shapes and textures, basically.
HAMILTON: Like faces, animals, plants, words, water bottles, sunglasses. The team focused on a brain area called the ventral temporal cortex, which is involved in recognizing objects, and they recorded which neurons fired in response to each image. They also noted how many times each neuron fired – part of the code the brain uses to communicate. Wadia says after each patient finished looking at the objects, he would leave the room.
WADIA: Then I would go back to the patient room and then do a sort of cued imagination task where I would have them close their eyes and imagine the object that I was telling them to imagine.
HAMILTON: Brain imaging studies have suggested that the same circuits are involved in both seeing and imagining. But technologies like FMRI can’t show what individual neurons are doing. Wadia says the new study monitored the exact neurons activated by seeing an object.
WADIA: About 40% of those neurons reactivated when you were imagining the object. And they reactivated with roughly equal strength, which is also very surprising.
HAMILTON: Because imagination is generally less vivid than direct experience. But in this experiment, just thinking about an object replicated much of the response produced by seeing the object. Ueli Rutishauser, also from Cedars-Sinai and Caltech, says the similarity was so strong that the team could easily tell if the patient was thinking about, say, an airplane.
UELI RUTISHAUSER: Oh, yes, and much more detail than that. Like, it’s so big, and it’s in this angle, and it’s outside or inside. Oh, yes.
HAMILTON: Rutishauser says a small number of people lack the ability to create mental images. He learned that while giving a talk at a scientific meeting.
RUTISHAUSER: Then afterwards, a very prominent and successful scientist came up to me, and she said, I don’t know what you’re talking about. I don’t see anything when I close my eyes.
HAMILTON: Rutishauser says these people appear to rely on words or concepts rather than images to remember an object. The research appears in the journal Science, and Thomas Naselaris, a neuroscientist at the University of Minnesota, says it helps explain an ability that is important for more than memory. He says it’s something we rely on whenever we look at a refrigerator or a car.
THOMAS NASELARIS: Objects are three-dimensional. They present themselves to us one side at a time, and yet, we intuitively and automatically seem to be able to model the parts of the object that we don’t see.
HAMILTON: Our brain tells us that car has a bumper on the back, even if it’s out of sight. Naselaris says mental images also allow us to assemble familiar objects into unfamiliar configurations.
NASELARIS: Like a horse with a horn – you know, a unicorn, right? We can imagine that, even though we’ve never seen one in real life.
HAMILTON: Probably thanks to the same neurons we use to see actual horses and actual horns. Jon Hamilton, NPR News.
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