Wednesday January 2 2013
On average, people blink around 15-20 times a minute
The Daily Mail suggests that the reason we blink is so our brains can "switch off" and have a "little nap".
The story is based on research in only 20 healthy adults in Japan looking at how natural blinking relates to brain activity. The study found that when these people blinked while watching a clip from the television show "Mr Bean", there was a reduction in activity in areas of the brain involved in paying attention to external stimuli (such as the video clip).
There was a corresponding increase in activity in some regions of the brain that are part of what is known as the default-mode network. Our default-mode network is thought to become active when our thoughts turn inwards and we are no longer focusing our attention on an external task.
This interesting research suggests that blinking may help our brains to switch off our attention briefly by activating the default-mode network, while reducing activity in other areas. It doesn't suggest our entire brain "switches off", which is not possible in a living person.
The brain is incredibly complex, and although this study can help provide clues about what is happening in the brain when we blink, and why, taken on its own it cannot yet provide a full understanding about blinking and brain activity.
Where did the story come from?
The study was carried out by researchers from Osaka University and the National Institute of Information and Communications Technology (NICT) in Japan. It was funded by the Japanese Ministry of Education, Culture, Sports, Science and Technology and the National Institute of Information and Communications Technology (NICT).
It was published in the peer-reviewed journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).
The Daily Mail provided reasonable coverage of this study, although their headline's suggestion that our brains "switch off" when blinking is incorrect – there is only a momentary reduction in activity in specific areas of the brain.
What kind of research was this?
This was an experimental study looking at whether brain activity changes when a person blinks. The researchers report that we blink far more often than we need to if blinking was only designed to lubricate our eyes. This raises the question of why we blink so much.
The researchers say that blinking tends to occur at natural breaks in attention, such as at the end of sentences when reading, pauses in speech, and moments in movies where there is less happening. They therefore wanted to test whether blinking might be a way of releasing our attention while we are concentrating on a mental task.
The volunteers' brains were scanned and activity in the areas of the brain related to attention were monitored during episodes of blinking while the volunteers were watching video clips. This study gives a good indication if the researchers' theory could be correct or not, but by itself it does not provide a complete understanding of the complex workings of the brain relating to attention and blinking.
What did the research involve?
The researchers asked 20 healthy adult volunteers to watch clips of the "Mr Bean" TV show while scanning their brains using a functional MRI (fMRI) scan and recording their eye movements. fMRI scanning tracks the flow of blood in the brain – increased blood flow in areas of the brain corresponds with increased neural activity in those areas, so the scans show which parts of the brain are more active at any given time.
The volunteers were shown clips of "Mr Bean" because previous research found that people watching the show blinked at similar times in natural breaks in the clip.
The researchers then looked at the brain scans and the timing of blinks to see whether brain activity changed at times when the volunteers blinked. They specifically looked at areas of the brain which are normally active when we pay attention to external stimuli (the dorsal attention network) and areas which are active when we are not paying attention to the external environment, and our minds may be active but processing information internally (the default-mode network).
They also looked at what happened with brain activity if they blacked out the screen briefly at random points during the video. This was because they wanted to check that the changes in brain activity were not caused by a sudden loss of visual information, but by the physical act of blinking itself.
What were the basic results?
The volunteers blinked about 17 times per minute on average while watching the video. They found that shortly after volunteers blinked, they had a momentary reduction in activity in the dorsal attention network and a momentary increase in activity in the default-mode network.
The same changes in brain activity were not seen when the screen was blacked out momentarily.
How did the researchers interpret the results?
The researchers say that their results suggest that blinking actively helps us to disengage our attention during a cognitive task. They say that this theory merits further research to test whether it is correct.
This interesting research suggests that blinking may help our brains to switch off our attention briefly by activating certain areas of the brain and reducing activity in other areas. The research doesn't suggest our entire brain "switches off", as the news headlines suggest.
The study only examined 20 healthy Japanese adults, so it may not be representative of what happens in people of different ages or who are unhealthy. The researchers say that other studies of blinking have not found the same patterns of brain activity. They suggest that this may be because the other studies looked at intentional eye blinking and asked the volunteers to look at simple pictures rather than videos. This indicates that the relationship between blinking and brain activity may vary in different situations.
The brain is incredibly complex, and this study in a few healthy adult volunteers helps to give clues, but cannot provide a full understanding of what is happening in the brain when we blink. For example, it can't tell us exactly how blinking might affect brain activity or why these momentary reductions in attention are important.
This study research on blinking may seem a little silly (especially as it uses clips of Mr Bean), but finding out more about exactly how the brain works in illness and in health is an important goal in neurology.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.