The study find that the brain activity cause people to see or not see complex images that flash before our eyes. Therefore An image can become practically invisible if it flashes before our ; because eyes at the same time as a low point of those brain waves. They  reset that brain wave rhythm with a simple voluntary action, like choosing to push a button.

Point of those brain waves

The new results come from experts who use optical illusions to understand human vision. Human sight involves activity both in the eyes and in the brain. Optical illusions ;are form by playing tricks on any part of our complex visual system. “This is the first record of rhythmic brain activity use to achieve integrated visual perception;” said Associate Professor Isamu Motoyoshi from the University of Tokyo and co-author of the recent research article.

Previous research identified that attention fluctuates six to eight times per second (6 to 8 Hertz); a rate researchers refer to as theta rhythms. The recent investigation started when Motoyoshi and colleagues were studying the Gabor pattern illusion; in which a smoothly moving circle appears to jump across the screen.

Rhythmic brain activity

Viewers saw jumps at a constant rhythm regardless of the actual speed of the illusion. The rhythm of jumps in the optical illusion was remarkably similar to the theta rhythm of brain waves related to attention. In their recent experiments, researchers asked participants to push a button to begin each trial, whenever they felt ready. Then after some unpredictable wait time, two images would quickly flash on a computer screen, one after the other. Participants then reported which images they saw.

“These tests are considered high cognitive load tasks. You have to identify both the light intensity white or black color and the orientation of the image left or right diagonal lines;” said Ryohei Nakayama, Ph.D., previously a project researcher in Motoyoshi’s lab and a currently a researcher at the University of Sydney, Australia.

Attention brain waves

Participants were much more likely to report correctly which images they saw when the images flashed at the same time as a high point of their attention brain waves, as measured by an EEG (electroencephalogram). The opposite was also true: Participants were more likely to give an incorrect answer when the images were flashed at the same time as a low point of their attention brain wave.

Theoretically, an image could become functionally invisible if it always flashed in time with the low points of theta rhythm attention brain waves. “Under certain conditions, attention is needed to achieve unified perception. That’s the classical story,” said Motoyoshi.