‘Why it doesn’t get dark when you blink’


Scientists have identified an area in the brain that allows people to see the world as a stable, unified whole despite blinking.

People blink every five seconds. During this brief moment, no light falls on the retina, yet people continue to observe a stable picture of the environment with no intervals of darkness.

Researchers at the German Primate Centerand the University Medical Center Gottingenand colleagues from the US performed studies on epilepsy patients to determine where this perceptual memory is situated in the brain, and how it works.

They have identified a brain area that plays a crucial role in perceptual memory.

The finding, published in the journal Current Biology, enables a better understanding of the interaction of perception and memory.

Despite blinking, people still see the world as a stable, unified whole, researchers said.

It must therefore be possible for the brainto retain visual information for a short period of time and then put it together to form a conclusive image without interruptions, they said.

Caspar Schwiedrzik from the German Primate Center and his team suspected that the medial prefrontal cortex, which plays an important role in short-term memory and decision-making, may be a key playerin this process.

At New York University in the US, scientists had studied this region of the brain in patients with epilepsy.

To treat the disease, electrodes were temporarily implanted in the brains of these patients.

Subjects were shown a dot lattice on a screen and were asked to indicate their perception of the vertical or horizontal orientation of the points.

They were then shown a second dot lattice and were asked to indicate the orientation of the points.

If both orientations were the same, this was interpreted as an indication that the subjects used the information from the first round to establish a conclusive percept in the second round.

While the subjects performed the task, neural activity in the prefrontal cortex was recorded. In one of the subjects, a section of the superior frontal gyrus was removed due to an earlier illness, and she was unable to store the visual information.

“Our research shows that the medial prefrontal cortex calibrates current visual information with previously obtained information, and thus enables us to perceive the world with more stability, even when we briefly close our eyes to blink,” said Schwiedrzik.

This is not only true for blinking, but also for higher cognitive functions.

“Even when we see a facial expression, this information influences the perception of the expression on the next face that we look at,” said Schwiedrzik.

“We were able to show that the prefrontal cortex plays an important role in perception and in context-dependent behaviour,” he said.

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