Seeing Is Deceiving

STATES OF MIND

Why can two witnesses, observing the exact same. event, provide two different accounts of what happened? one reason: what we see may literally depend on our state of mind.

Using a new technique in which a voltage-sensitive dye actually lights up busy brain cells, researchers have discovered that the way our brain represents what we see is influenced by our thoughts and moods at the time. And they can tell what an eye is seeing just by monitoring patterns of brain activity

It's long been known that when someone sees the same image over and over, his brain reacts differently each time. Scientists chalked up that kaleidoscope of responses to random brain signals, or "noise."

But researchers at Israel's Weizmann Institute realized that this supposedly random activity is really quite organized. It simply reflects our ever-shifting series of thoughts, feelings, and memories—"the many simultaneously ongoing conversations of the brain with itself," says Amos Arieli, Ph.D.

By monitoring these mental conversations, Arieli and colleagues can predict the exact pattern of brain activity that results when they show an image to a cat. More remarkably, by comparing "before" and "during" patterns of activity in the cat's visual cortex, "we can tell what the eye just saw for a very simple picture," Arieli told the Society for Neuroscience.

Scientists are still far from being able to peek into your mind and tell that you're admiring a Picasso watercolor rather than, say, a cartoon of Lucy yanking the football from under Charlie Brown's feet. But they've taken the first step.

PHOTO (COLOR)