Berkeley: Every few seconds, our eyelids automatically shutter and our eyeballs roll back in their sockets. So why doesn’t blinking plunge us into intermittent darkness and light? New research led by UC Berkeley shows that the brain works extra hard to stabilize our vision despite our fluttering eyes. Scientists at UC Berkeley, Nanyang Technological University in Singapore, Dartmouth College and Université Paris Descartes have found that blinking does more than lubricate dry eyes and protect them from irritants.
In a study published today in the online edition of the journal Current Biology, they found that when we blink, our brain repositions our eyeballs so we can stay focused on what we’re viewing.
When our eyeballs roll back in their sockets during a blink, they
don’t always return to the same spot when we reopen our eyes. This
misalignment prompts the brain to activate the eye muscles to realign
our vision, said study lead author Gerrit Maus, an assistant professor
of psychology at Nanyang Technological University in Singapore. He
launched the study as a postdoctoral fellow in UC Berkeley’s Whitney Laboratory for Perception and Action.
“Our eye muscles are quite sluggish and imprecise, so the brain needs
to constantly adapt its motor signals to make sure our eyes are
pointing where they’re supposed to,” Maus said. “Our findings suggest
that the brain gauges the difference in what we see before and after a
blink, and commands the eye muscles to make the needed corrections.”
From a big-picture perspective, if we didn’t possess this powerful
oculomotor mechanism, particularly when blinking, our surroundings would
appear shadowy, erratic and jittery, researchers said.
“We perceive coherence and not transient blindness because the brain
connects the dots for us,” said study co-author David Whitney, a
psychology professor at UC Berkeley.
“Our brains do a lot of prediction to compensate for how we move
around in the world,” said co-author Patrick Cavanagh, a professor of
psychological and brain sciences at Dartmouth College. “It’s like a
steadicam of the mind.”
A dozen healthy young adults participated in what Maus jokingly
called “the most boring experiment ever.” Study participants sat in a
dark room for long periods staring at a dot on a screen while infrared
cameras tracked their eye movements and eye blinks in real time.
Every time they blinked, the dot was moved one centimeter to the
right. While participants failed to notice the subtle shift, the brain’s
oculomotor system registered the movement and learned to reposition the
line of vision squarely on the dot.
After 30 or so blink-synchronized dot movements, participants’ eyes
adjusted during each blink and shifted automatically to the spot where
they predicted the dot to be.
“Even though participants did not consciously register that the dot
had moved, their brains did, and adjusted with the corrective eye
movement,” Maus said. “These findings add to our understanding of how
the brain constantly adapts to changes, commanding our muscles to
correct for errors in our bodies’ own hardware.”
In addition to Maus, Whitney and Cavanagh, co-authors of the study
are Marianne Duyck, Matteo Lisi and Therese Collins of the Université