Glance at a newsmagazine and you probably recognize the face on the cover right away–Al Gore looking serious in profile, or perhaps a smirking Dick Cheney. But in that instant, your brain performs a lot of complex computations: identifying the object as a face (regardless of size or viewing angle), interpreting its expression, and accessing memory to determine whether it’s familiar.
Little is known about how the brain does all that, but Doris Tsao aims to unravel the process by combining two of the most important tools in neuroscience: brain imaging and electrical recordings from single neurons.
Last year, Tsao used functional magnetic resonance imaging, a technology that indirectly measures brain activity, to identify areas of the monkey brain that are active only when the animals look at faces. She then used a detailed MRI picture to guide an electrode to several of those spots. Using the electrode to record activity from individual neurons, she found that different cells respond to different facial characteristics–say, the shape of the face or the size of the eyes. This exquisite level of detail would have been impossible with imaging alone.
Tsao’s work yields important clues to how neural activity leads to conscious visual perception, says Christof Koch, a neuroscientist at Caltech. “It’s a step toward answering the age-old question ‘What is the relation between the mind and the brain?’”