On the origin of event-related potentials indexing covert attentional selection during visual search.

Despite nearly a century of electrophysiological studies recording extracranially from humans and intracranially from monkeys, the neural generators of nearly all human event-related potentials (ERPs) have not been definitively localized. We recorded an attention-related ERP component, known as the N2pc, simultaneously with intracranial spikes and local field potentials (LFPs) in macaques to test the hypothesis that an attentional-control structure, the frontal eye field (FEF), contributed to the generation of the macaque homologue of the N2pc (m-N2pc). While macaques performed a difficult visual search task, the search target was selected earliest by spikes from single FEF neurons, later by FEF LFPs, and latest by the m-N2pc. This neurochronometric comparison provides an empirical bridge connecting macaque and human experiments and a step toward localizing the neural generator of this important attention-related ERP component.