Researchers find that blinking plays a pivotal role in processing visual information鈥攁dding to a growing body of evidence revising our conventional views of vision.
The ordinary act of blinking takes up a surprising amount of our waking time. Humans, on average, spend a remarkable 3 to 8 percent of their awake time with their eyelids closed.
Given that blinks prevent an image of the external scene from forming on the retina, it鈥檚 a peculiar quirk of evolution that we spend so much time in this seemingly vulnerable state鈥攅specially considering that eye blinks occur more frequently than necessary just to keep our eyes well lubricated.
So, why is blinking important?
Researchers from the investigated the curious case of blinking and found that eye blinks aren鈥檛 just a mechanism to keep our eyes moist; blinks also play an important role in allowing our brains to process visual information. The researchers in the Proceedings of the National Academy of Sciences.
鈥淏y modulating the visual input to the retina, blinks effectively reformat visual information, yielding luminance signals that differ drastically from those normally experienced when we look at a point in the scene,鈥� says , a professor in the .
In other words, a lot more happens in the blink of an eye than meets the eye.
The big picture鈥攊n the blink of an eye
Rucci and his colleagues tracked eye movements in human observers and combined this data with computer models and spectral analysis鈥攁nalyzing the various frequencies in visual stimuli鈥攖o study how blinking affects what the eyes see compared to when the eyelids are closed.
The researchers measured how sensitive humans are at perceiving different types of stimuli, such as patterns at different levels of details. They found that when people blink, they become better at noticing big, gradually changing patterns. That is, blinking provides information to the brain about the overall big picture of a visual scene.
The results show that when we blink, the rapid motion of the eyelid alters the light patterns that are effective in stimulating the retina. This creates a different kind of visual signal for our brain compared to when our eyes are open and focused on a specific point.
鈥淣eurons respond strongly to temporal changes in their input signals and tend to not respond to unchanging stimuli,鈥� says Bin Yang, a graduate student in Rucci鈥檚 lab and the first author of the paper. 鈥淲ith their abrupt transients, blinks make the visual system respond strongly to the image on the retina. Thus, contrary to common assumption, blinks improve鈥攔ather than disrupt鈥攙isual processing, amply compensating for the loss in stimulus exposure.鈥�
Revising a view of vision
The findings further reinforce the growing body of research in visual perception from Rucci鈥檚 laboratory, highlighting that how humans see is a combination of sensory input and motor activity. When we smell or touch, for instance, our body movements help our brain understand space. Researchers previously believed seeing was different, but Rucci鈥檚 research lends support to the idea that vision is more like the other senses.
鈥淪ince spatial information is explicit in the image on the retina, visual perception was believed to differ,鈥� Rucci says. 鈥淥ur results suggest that this view is incomplete and that vision resembles other sensory modalities more than commonly assumed.鈥�
