What would our daily lives be like if we actually experienced each blink of an eye as a miniblackout, slowly observing the eyelids closing over the cornea thousands of times a day?
Luckily, we don't have to endure that chaos, and researchers have uncovered a clue as to why. Dr. Davina Bristow and colleagues at University College London equipped the mouths of volunteers with optical fibers that allowed their retinas to experience a continuous stream of light. Subjects also shielded their eyes with lightproof goggles. The researchers then used functional MRI to measure brain activity associated with blinking. (Current Biology 2005;15:1296-1300).
They found a synchronized link between blinking and the suppression of areas of the brain that process visual awareness. When volunteers blinked, parts of their visual cortex shut down, even though the light falling onto the retina remained constant throughout the blink.
The brain, essentially, is hardwired not to notice the thousands of daily nanosecond blackouts, the researchers concluded.