Is what you think you see really what you see?
A few years ago, University of California, Berkeley researchers managed to do something that had never before been accomplished, except perhaps in science fiction. Using a technology called functional Magnetic Resonance Imaging
Is what you think you see really what you see?
A few years ago, University of California, Berkeley researchers managed to do something that had never before been accomplished, except perhaps in science fiction. Using a technology called functional Magnetic Resonance Imaging, or fMRI, to pick up brain activity and a computer modeling program to analyze the patterns of neural impulses, they essentially were able to peer inside people’s brains and view what they were seeing at a particular moment. When the experimental subjects watched a video image of an elephant, an airplane, or actor Steve Martin as Inspector Clouseau in the remake of “The Pink Panther,” the researchers could see a murky, but usually recognizable, reconstruction of the image on their
own screen. “This a major leap toward reconstructing internal imagery,” explained UC Berkeley neuroscientist Jack Gallant, a coauthor of the study published in Current Biology in 2011. "We are opening a window into the movies of our minds."
Amazing as the scientists’ breakthrough was, it was nowhere near as difficult as feats that your own brain routinely pulls off every moment of your waking existence.
Though we have five different senses, almost a third of your brain is devoted to vision. That’s because sight plays a particularly crucial role in helping you to make sense of the reality around us and perform the myriad activities of our daily lives. Your eyes and your brain work together to make sense of a vast, continual stream of visual information. To cope with that demand, the human brain has developed various tricks and shortcuts that enable us to quickly do everything from recognize other people’s faces, to the position
and relative size of the objects around us. Conversely, though, the brain’s reliance on those gimmicks makes it vulnerable to being fooled by optical illusions and magicians’ slight-of-hand tricks. Scientists even have utilized such deceptions to demonstrate how the brain’s visual processing of reality works, and what are its built-in limitations.
Making the Movie Inside Your Head
You rely heavily upon what you see to make sense of reality, and to help you to figure out what to do from moment to moment, whether you’re trying to thread a needle or find where you left your car keys. The task of constructing that visual map of your environment falls to the visual-processing centers of your brain, and it’s a really, really tough job. Researchers at the University of Pennsylvania’s School of Medicine estimate that each of your retinas are capable of transmitting 10 million bits of information every second, which makes it comparable to the Ethernet connection on a typical computer network (10 million to 100 million bits).
That cascade of data is transmitted along a pair of optic nerves, which become intertwined and switch sides along the way to your brain’s visual processing area. (That means that the left half of your field of vision actually is perceived by the
right hemisphere of your brain, and vice-versa.) As that information makes its way to the main visual processing areas in the rear of your brain, the primary and secondary visual cortexes, it passes through other parts of the brain, which also make use of some of the data. In the middle of the brain, for example, part of your hypothalamus taps into some of the visual data about whether the environment around you is dark or brightly lit. It uses that information to adjust to the cycle of day and night, and to synchronize biological rhythms that help you to sleep and to awaken in the morning. Meanwhile, another area of the brain, the pulvinar nucleus in the thalamus, also grabs a little bit of data, which it uses to help stabilize your view of the world as you move, sort of like the anti-shake feature on a fancy video camera.
But it’s the main processing areas, the primary and secondary visual cortexes in the back of the brain, which sift through most of the visual data, making sense of the sea of color,
shape and movement around you. They organize the info and send it along one of two main relays back to the parts of the brain that need it. The dorsal visual pathway, which goes to the brain’s parietal lobe, provides data that helps you to figure out the spatial relationships between our bodies and objects in the environment, so that you can interact with them. If you’re walking across your office, it’s what helps to keep you from banging into the walls or tripping over your
coworker’s trash basket. The ventral visual pathway, in contrast, which goes to the brain’s temporal lobe, contains data that helps you to figure out the identity of objects. It’s what helps you to perceive that the thing on the counter of the break room is a delicious-looking cherry Danish, rather than a stapler.
How the brain organizes, retains, and utilizes all that visual data is even more, well, mind-boggling. In ano