Why it's not dark when you blink

People blink every five seconds. During this brief moment, no light falls on the retina, but people continue to observe a stable image of the environment without intervals of darkness. Caspar Schwiedrzik and Sandrin Sudmann, neuroscientists from the German Primate Center and the University Medical Center Göttingen and colleagues from the United States have conducted studies on epileptic patients to determine where this perceptual memory is in the brain. They identified a brain zone that plays a crucial role in perceptual memory. This discovery helps to better understand the interaction of perception and memory. The study is published inCurrent Biology.

Despite the blinking, people still see the world as a stable and unified whole. It must be possible for the brain to retain visual information for a short time, then assemble it to form a conclusive image without interruption. Caspar Schwiedrzik and his team of neuroscientists have suspected that the medial prefrontal cortex, which plays an important role in short-term memory and decision-making, could play a key role in this process.

At New York University, scientists have had the opportunity to study this region of the brain in patients with epilepsy. To treat the disease, electrodes have been implanted temporarily in the brains of these patients. The subjects showed a network of dots on a screen and were asked to indicate their perception of the vertical or horizontal orientation of the dots. They were then shown a second network of points and asked them to indicate the points orientation. If the two orientations were identical, this was interpreted as an indication that the subjects used the information from the first round to establish a conclusive perception in the second round. As subjects performed the task, neuronal 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 could not store the visual information.

"Our research shows that the medial prefrontal cortex calibrates current visual information with previously obtained information and thus allows us to perceive the world with greater stability, even when we briefly close our eyes to blink," says Caspar Schwiedrzik and scientists of the German Primate Center and the Göttingen University Medical Center. 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 we are looking at," says Schwiedrzik.

"We have been able to show that the prefrontal cortex plays an important role in perception and context-dependent behavior," says Schwiedrzik, summarizing the results of the study. In other studies, researchers want to study, among other things, the role that trust plays in one's perception in perceptual memory.

Explore more:
Bridging the gap between human memory and perception

More information:
Caspar M. Schwiedrzik et al. The medial prefrontal cortex supports perceptual memory, Current Biology (2018). DOI: 10.1016 / j.cub.2018.07.066