title: Enhancement and suppression in the visual field under perceptual load.
abstract: The perceptual load theory of attention proposes that the degree to which visual distractors are processed is a function of the attentional demands of a task-greater demands increase filtering of irrelevant distractors. The spatial configuration of such filtering is unknown. Here, we used steady-state visual evoked potentials (SSVEPs) in conjunction with time-domain event-related potentials (ERPs) to investigate the distribution of load-induced distractor suppression and task-relevant enhancement in the visual field. Electroencephalogram (EEG) was recorded while subjects performed a foveal go/no-go task that varied in perceptual load. Load-dependent distractor suppression was assessed by presenting a contrast reversing ring at one of three eccentricities (2, 6, or 11°) during performance of the go/no-go task. Rings contrast reversed at 8.3 Hz, allowing load-dependent changes in distractor processing to be tracked in the frequency-domain. ERPs were calculated to the onset of stimuli in the load task to examine load-dependent modulation of task-relevant processing. Results showed that the amplitude of the distractor SSVEP (8.3 Hz) was attenuated under high perceptual load (relative to low load) at the most proximal (2°) eccentricity but not at more eccentric locations (6 or 11°). Task-relevant ERPs revealed a significant increase in N1 amplitude under high load. These results are consistent with a center-surround configuration of load-induced enhancement and suppression in the visual field.
authors.affiliation: Beckman Institute, University of Illinois Urbana-Champaign Urbana, IL, USA ; Department of Psychological Science, University of Arkansas Fayetteville, AR, USA.
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Parks
authors.forename: Diane M
authors.initials: DM
authors.lastname: Beck
authors.forename: Arthur F
authors.initials: AF
authors.lastname: Kramer
keywords: N1; attention; perceptual load; steady-state visual evoked potential (SSVEP)