Zasto ne primecujemo kad sami trepcemo

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Scientists have figured out why we rarely notice our own blinking. Our brains simply miss it, they say.

The quest for the new discovery began in the 1980s, when researchers found that visual sensitivity starts decreasing just before we blink. But what goes on in the brain remained a mystery.

In the new study, scientists put fiber-optic lights in the mouths of people. The lights were powerful enough to penetrate the roofs of their mouths and strike their retinas, where light is recorded. They wore goggles to block outside light.

When the test subjects blinked, the amount of light hitting their retinas didn't change. Activity in their brains was monitored by functional magnetic resonance imaging.

During blinking, brain activity was suppressed in areas that respond to visual input, the scientists report.

"Transiently suppressing these brain areas involved in visual awareness during blinks may be a neural mechanism for preventing the brain from becoming aware of the eyelid sweeping down over the pupil during a blink and the world going dark," said Christopher Frith at the University College London.

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Pogrešan je naslov.. nije "Zašto trepćemo", nego "Zašto ne primećujemo kada sami trepćemo"

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Trepni i propustices

Why doesn't the world go dark when we blink? Because a critical part of the brain switches off and fails to detect the blackness behind closed eyes, says a team of neuroscientists.

We blink about ten times a minute without noticing any change in what we see. Researchers had suspected that this is because the visual system is inactivated during blinking, but were not able to prove this.

A team at University College London have razbijaced the problem by inserting an optical fibre into the mouths of people wearing black-out goggles. The fibre illuminated the back of the subjects' retinas, so that they saw a light at all times, even when they blinked. This allowed the researchers,to distinguish between the effects of the act of blinking and the darkness that it causes.

Using magnetic resonance imaging (fMRI) brains scans, Davina Bristow and colleagues revealed that activity in a part of the visual system known as V3 was suppressed in subjects when they blinked. V3 is one of a series of brain areas that handle signals sent from the eyes. With it out of action, the blink goes unnoticed.

"It's not that the visual gap is filled in," says Bristow. "It's that you're not aware of it."

Blinded by the light

Similar inactivation is known to allow us to see a smooth image even when our eyes jump between two parts of a scene. But working out what happens in the brain during blinking has proven very difficult.

Blinks normally cause an abrupt change in the amount of light reaching the retina, which in turn causes a massive change in brain activity in the visual region. Seeing any effect in the V3 area has been obscured by this in the past.

"Blinks are hard to study," says Tim Gawne, a vision researcher at the University of Alabama in Birmingham.

Blinking is not the only process that causes areas of the brain to be suppressed. Bristow points out that fMRI scans have shown that tactile areas of the brain are suppressed when we tickle ourselves, but not when someone else does it

Bristow says studies of tickling and blinking add to our understanding of how our brains deal with different types of events.

"How do we distinguish between what is caused by you and what is caused by the outside world?" she asks. "It's more important, for all animals, to pay attention to outside causes. Blinking is a way of studying how they do so."


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Dijelovi mozga su privremeno 'isključeni' kada trepnemo. To bi, smatraju znanstvenici, moglo objasniti zašto ljudi ne primjećuju vlastito treptanje.



Znanstvenici s Londonskog sveučilišta otkrili su da mozak 'isključi' dijelove povezane s vizualnim sustavom kada god čovjek trepne, čak i ako svjetlo i dalje ulazi u oko.

To bi moglo objasniti zašto ljudi ne primjećuju vlastito treptanje, tvrde britanski znanstvenici.

U istraživanju je upotrebljena specijalna naprava koja je proučavala učinke treptanja na mozak.

Načinjena je od optičkog kabela koji je stavljen u usta dobrovoljcima opremljenima naočalama otpornima na svjetlost, koji su ležali u skeneru za magnetsku rezonancu. Optičko vlakno bi osvijetlilo očnu jabučicu kroz nepce koristeći se jakom svjetlošću.

To znači da je svjetlo koje je padalo na očnu mrežnicu bilo tamo čak i kada su sudionici istraživanja treptali.

Znanstvenici su otkrili da treptanje 'gasi' aktivnosti mozga u vizualnom korteksu i drugim dijelovima mozga koji su inače aktivirani kada su ljudi svjesni vizualnih događaja ili predmeta u vanjskom svijetu.




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