Reading people's minds with brain scanners is the stuff of science fiction. But two teams of scientists have brought that prospect a step closer by deciphering aspects of images people see--even ones that enter the brain unconsciously.
Exactly how the brain stores information in its vast, complex wiring is still a mystery. But researchers have made headway with a posterior part of the brain called the visual cortex. Groups of neurons in this region process some of the basic aspects of what we see, such as color, motion, and location. Studying this neural wiring in humans is difficult because the only technique available to track brain activity in real time, called functional magnetic resonance imaging (fMRI), does not yet have the resolution to watch individual neurons at work.
Two groups of researchers have done the next best thing: They each designed computer programs that detect patterns of activity across populations of visual cortex neurons. Yukiyasu Kamitani and Frank Tong, neuroscientists at ATR Computational Neurosciences Laboratories in Kyoto, Japan, and Vanderbilt University in Nashville, Tennessee, respectively, used a program to track blood flow in the visual cortex while they showed people pictures of black and white stripes. Different stripe orientations activated particular columns of neurons that seem to react to specific angles in the outline of objects. The researchers found they could use the fMRI technique to determine accurately which images the subjects were shown--effectively allowing the scientists to read their minds, at least at a basic visual level.
The method can even detect the perception of images of which people aren't aware. John-Dylan Haynes and Geraint Rees, neuroscientists at University College London, U.K., flashed pictures of stripes too quickly for people to notice their orientation. But fMRI activity revealed that groups of neurons had still detected these fleeting images. The result lends further support to the theory that the visual cortex processes visual information subconsciously, say the researchers, who, along with the other team, published their work online 24 April in Nature Neuroscience.
The studies are progress towards building a "translator" that researchers could use to decode thoughts from the brain's electrical impulses, says James Haxby, a neuroscientist at Princeton University in New Jersey and part of the team that first introduced the fMRI method of tracking whole neuron populations at once (Science, 28 September 2001, p. 2425). Armed with such a translator, Haxby says, neuroscientists may finally be able to reveal how the information behind our thoughts is stored and processed.