How brain controls vision and why we leave things out even when in plain sight


Out of Mind, Out of Sight!

Research indicates the brain’s frontal cortex controls vision; it omits things in plain sight

Researcher Dobromir Rahnev, who led the study, sits in the Georgia Tech control room of a functional MRI scanner much like the one used at the University of California, Berkeley for experiments on the frontal cortex’s role in creating vision. Credit: Georgia Tech

Ever search desperately for something, then realize you were looking straight at it the whole time? Research indicates that vision is controlled by the part of the brain associated with thinking. And in sight, too, it can be absent minded.

Dobromir Rahnev, a psychologist at the Georgia Institute of Technology leads a research team making new discoveries about how the brain organizes visual perception, including how it leaves things out even when they’re plainly in sight.

Rahnev and researchers from the University of California, Berkeley have come up with a rough map of the frontal cortex’s role in controlling vision. They published their findings on Monday, May 9, 2016 in the journal Proceedings of the National Academy of Sciences.

Thinking cap

Brain image from a functional MRI scan during tests on the role of the frontal cortex in vision. It’s the part of the brain known for being the “thinking cap.” Credit: Georgia Tech

The frontal cortex is often seen as our “thinking cap,” the part of the brain scientists associate with thinking and making decisions. But it’s not commonly connected with vision. “Some people believe that the frontal cortex is not involved,” said Rahnev, an assistant professor at the School of Psychology. The new research adds to previous evidence that it is, he said.

The lack of association with that part of the brain may have to do with the fact it’s other parts that transform information coming from the eyes into sight and others still that make sense of it by doing things like identifying objects in it.

But the thinking cap of the brain controls and oversees this whole process, making it as essential to how we see as those other areas, Rahnev said. How that works also accounts for why we sometimes miss things right in front of us.

A camera it’s not

“We feel that our vision is like a camera, but that is utterly wrong,” Rahnev said.  “Our brains aren’t just seeing, they’re actively constructing the visual scene and making decisions about it.”  Sometimes the frontal cortex isn’t expecting to see something, so although it’s in plain sight, it blots it out of consciousness.

To test out the fontal cortex’s involvement in vision, the researchers ran a two-part experiment.

First, they observed which regions of the brain — in particular the frontal cortex – lit up with activity while healthy volunteers completed visual tasks corresponding to three basic stages of conscious visual perception.

Second, they inhibited those same regions using magnetic stimulation to confirm their involvement in each visual stage.

Believing is part of seeing

When temporary magnetic stimulation was applied to target areas of the brain, it affected the way test subjects performed aspects of visual tasks. Credit: Georgia Tech

The first stage of the visual perception the researchers tested for was selection, Rahnev said. That’s when the brain picks out part of the vast array of available visual stimuli to actually pay attention to.

The second stage is combination, he said. The brain merges the visual information it processed with other material. Then comes evaluation.

“The frontal cortex sends a signal to move your attention onto the object you select,” Rahnev said. “It does some of the combining with other information, and then it’s probably the primary evaluator of what you think you saw.”

The critical evidence

Researcher Dobromir Rahnev demonstrates the application of temporary magnetic stimulation (TMS) in a Georgia Tech psychology research center with graduate student Ji-Won Jung. This type of stimulation was used at the University of California, Berkeley for experiments on the frontal cortex’s role in creating vision. Credit Georgia Tech

The critical evidence for this map came from the use of magnetic stimulation. When the researchers used it to inhibit the back and middle of the frontal cortex separately, subjects became less able to complete the corresponding functions of selection and combination.

When they stimulated the front, the opposite happened. Subjects were slightly but significantly better able to evaluate the accuracy of what they think they saw.

“This is a really clear demonstration of the role that the frontal cortex, which is usually seen as the seat of thought, plays in controlling vision.”

Practical implications for health and safety!

And there is a practical takeaway for health and safety. Often we hear motorists telling police officers,  “I swear I didn’t see that coming,” after a car accident.

Distraction is often the culprit, because it overtaxes the organization of perception, Rahnev said. These three functions are going on all the time in multiple scenarios in our brains while they process the world around us.

But add too much to the pile, like texting behind the wheel, Rahnev said, and “you can run right into a parked car without ever seeing it.”

Source: Georgia Tech