The tenet of functional neuroimaging is that the difference between two tasks can be formulated as a separable cognitive or sensorimotor component and that the regionally specific differences in brain activity identify the corresponding specialized area. The first applications addressed the functional anatomy of word processing (Peterson, Fox, Posner, Mintun, & Raichle, 1989) and functional specialization in extrastriate cortex (Lueck et al., 1989). The latter studies involved presenting visual stimuli with and without some sensory attribute (e.g., color, motion, etc.). The areas high lighted, by comparing the ensuing scans, were identified with homologous areas in monkeys that showed selective electrophysiological responses to equivalent stimuli. Most studies of functional specialization employ statistical parametric mapping (Friston, 1997) to provide what can be thought of as X rays of significant brain responses (see Figure 1). These statistical parametric maps (SPMs) are constructed using a series of brain scans acquired from subjects under experimentally induced changes in brain state, designed to isolate the function of interest. The cortical area in the lower right of Figure 1 is visual area V5 and shows significant motion-sensitive responses elicited by alternate presentations of stationary and moving dots.
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