Visualizing the Mind; April 1994; Scientific American Magazine; by Raichle; 7 Page(s)
What causes the pity we might 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 "black box" description of the brain, however, fails to pinpoint the specific 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 analytically--to 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 specific regions of the brain "light up" 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 differences 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 identified by bumps on the skull, uniquely represented specific thought processes and emotions. In contrast, modern thinking posits that networks of neurons residing in strictly localized areas perform thought processes. So just as specific 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 finally create mental images.