Electrophysiological Correlates of the Focusing of Attention within Complex Visual Scenes: N2pc and Related ERP Components

Th e General Role of Attention in Visual Perception Th e ultimate goal of research on visual perception is to understand how people perceive, remember, and act upon the objects in natural visual environments, such as the scene shown in Figure 12.1 . Understanding these high-level aspects of vision requires that we understand the operation of almost the entire brain, because visually guided behavior depends on perceptual systems, memory systems, motor systems, motivational systems, and executive control systems. Th e perception of complex scenes also involves solving computational problems that are not present in laboratory experiments in which objects are presented one at a time on a blank background (see Feldman, 1985 ; Luck et al., 1997b ). Whereas simple, isolated stimuli may be identifi ed on the basis of a single feedforward sweep of neural activity, the perception of complex, multiple-element arrays involves iterative, reentrant processes and perception-action loops (see Di Lollo et al., 2000 ; Klyubin et al., 2004 ). As discussed in Chapter 11 of this volume, attention plays a role in the perception of simple stimuli, serving as a gain control that enhances the speed or accuracy of feedfor ward visual processing. However, additional attentional mechanisms are needed to support the iterative, reentrant processes and perception-action loops that are invol ved in the perception of complex, multipleelement stimulus arrays, and the event-related potential (ERP) correlates of these additional attentional mech anisms will be the focus of the present chapter. We will begin by discussing the computational problems that must be solved by these mechanisms and the sequence of steps involved in processing complex stimulus arrays. Abstract