Bridging the gap between monkey neurophysiology and human perception: an ambiguity resolution theory of visual selective attention.

When the visual system must process multiple objects simultaneously, as in the visual search paradigm, the neural coding of individual objects can become ambiguous due to the visual system's extensive use of coarse coding and distributed representations. Here we propose that the primary role of visual selective attention within the ventral object recognition pathway is to resolve these ambiguities. We begin by reviewing previous studies of the effects of attention on neural responses in monkeys, which provide the basis for this hypothesis, and then describe a new set of experiments showing that similar attentional mechanisms operate in the human brain. In these new experiments, event-related potentials (ERPs) were recorded from normal human observers while they performed tasks analogous to those used previously in monkeys. The central finding was that an attention-related ERP wave called the "N2pc component" was present under the same conditions that led to attentional modulations of neural responses in monkey visual cortex. These human electrophysiological results provide a bridge between cognitive-level theories of visual attention and the behavior of individual neurons in visual cortex.