Visualizing the Mind Strategies of cognitive science and techniques of modern brain imaging open a window to the neural systems responsible for thought by Marcus

feel for the melancholy Dane in Hamlet or the chill during a perusal of the Raven? Our brains have absorbed from our senses a printed sequence of letters and then converted them into vivid mental experiences and potent emotions. The Òblack boxÓ description of the brain, however, fails to pinpoint the speciÞc neural processes responsible for such mental actions. While philosophers have for centuries pondered this relation between mind and brain, investigators have only recently been able to explore the connection analyticallyÑto peer inside the black box. The ability stems from developments in imaging technology that the past few years have seen, most notably positron-emission tomography and magnetic resonance imaging. Coupled with powerful computers, these techniques can now capture in real time images of the physiology associated with thought processes. They show how speciÞc regions of the brain Òlight upÓ when activities such as reading are performed and how neurons and their elaborate cast of supporting cells organize and coordinate their tasks. The mapping of thought can also act as a tool for neurosurgery and elucidate the neural diÝerences of people crippled by devastating mental illnesses, including depression and schizophrenia. I hasten to point out that the underlying assumptions of current brain mapping are distinct from those held by early phrenologists. They posited that single areas of the brain, often identiÞed by bumps on the skull, uniquely represented speciÞc thought processes and emotions. In contrast, modern thinking posits that networks of neurons residing in strictly localized areas perform thought processes. So just as speciÞc members of a large orchestra perform together in a precise fashion to produce a symphony, a group of localized brain areas performing elementary operations work together to exhibit an observable human behavior. The foundation for such analyses is that complex behaviors can be broken down into a set of constituent mental operations. In order to read, for example, one must recognize that a string of letters is a word; then recognize the meaning of words, phrases or sentences; and Þnally create mental images. The challenge, of course, is to determine those parts of the brain that are active and those that are dormant during the performance of tasks. In the past, cognitive neuroscientists have relied on studies of laboratory animals and patients with localized brain injuries to gain insight into the brainÕs functions. Imaging techniques, however, permit us to visualize safely the anatomy and the function of the normal human brain.