Why can't I wink

Why doesn't it get dark when you blink?

Actually, it should go black before our eyes every few seconds: Whenever we blink. In fact, interestingly enough, this does not happen - we also see when we blink. A study shows why this is so. Accordingly, the middle prefrontal cortex in the brain functions as a kind of perceptual memory. He compares current visual impressions with previously obtained information and in this way can bridge short gaps in perception with stored information.

It doesn't help: every few seconds we have to blink to moisten our eyes. During this time, no light falls on our retina and we miss what is happening around us. But our brain makes us believe something else. Because even when we blink, we continue to see a stable picture of the environment in front of us. Our thinking organ seems to have a kind of memory for what has just been seen and to be able to bridge short interruptions with this visual information. But where is this perceptual memory? Caspar Schwiedrzik from the University of Göttingen and his colleagues had long suspected a certain region: the middle prefrontal cortex, which, among other things, plays a role in short-term memory and decision-making.

Memory effect in terms of perception

The neuroscientists then checked their theory with the help of epilepsy patients. The test subjects were temporarily implanted with fine electrodes in the brain to treat their disease. This opened up the possibility to, as it were, watch them think and examine the middle prefrontal cortex more closely. For their study, the researchers showed the test subjects a grid of points on a screen. You should then indicate in which orientation you perceived the points shown - for example horizontally or vertically. Then they saw a second grid of points.

It became apparent that the test subjects often indicated the same orientation the second time as they did the first time. Schwiedrzik and his team took this as a sign that they had used the information from the first round to infer the second. In the brains of these test subjects, the scientists found increased activity in certain areas of the prefrontal cortex. But was this region of the brain actually responsible for the observed phenomenon? The decisive evidence was provided by a patient from whom this area in the brain had been partially removed: She did not have the memory effect - she could not deduce the current task from the previous information, as the team reports.

Memory content influences visual impression

"Our studies show that the middle prefrontal cortex compares current visual information with previously obtained information and thus contributes to our perception of the world in a stable manner - even if we close our eyes briefly when blinking, for example," says Schwiedrzik. This applies not only to blinking, but also to higher cognitive performance: "Even if we see a facial expression, this information influences the perception of the next face that we look at," explains the researcher.

Source: Caspar Schwiedrzik (University of Göttingen) et al., Current Biology, doi: 10.1016 / j.cub.2018.07.066

17th September 2020

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