FUNCTIONAL Magnetic Resonance Imaging
Few scientific developments have been more striking than the ability to image the functioning human brain. Why do images of the brain evoke such wonder? To many, the human brain represents a barely explored new world, with each image providing a glimpse of hidden structure. Like the maps used by early explorers, our current understanding of brain function is riddled with errors, inconsistencies, and puzzles deserving of solution. Yet the difficulty in understanding the brain has only added to the excitement of the quest. The first popular mapping of brain function was proposed by the paleologists in the early nineteenth century. The phrenologists believed that the amount of brain tissue devoted to a cognitive function determined its influence on behavior. Although they were unable to measure cortical volume directly, they assumed that increases in brain size would translate into measurable bumps on the skull. So, a devoted mother should have a protrusion over the brain area supporting "love for one's offspring," whereas a common thief should have a flattening of the skull above the area supporting "honesty" (Figure 1.1). The most prominent advocates, notably Franz Joseph Gall and Johann Spurzheim, lectured widely on the new maps of brain function they had developed. Popular books used phrenology to explain differences among individuals, to provide self-improvement advice, and to advise employers on qualities desired for workers.