Abstract
Goal: Feature-based attention (FBA) enhances the processing of stimuli that are spatially coextensive with distractors that must be ignored. For some feature dimensions (e.g., color and motion), FBA increases sensitivity to the feature value that distinguishes the target - both at the target location and, remarkably, at ignored or unstimulated locations across the visual field. Several studies have demonstrated location-specific effects of attention to an oriented target that overlaps with a differently-tilted distractor, but there is little evidence for a spatial spread of orientation-based attention. Methods: We developed a novel psychophysical paradigm to measure the spread of orientation-based attention to peripheral locations where the attended feature is irrelevant. At the center of the display, a group of leftward tilted white lines overlapped with a group of rightward tilted white lines. Each of these groups pulsed in luminance at random times throughout the trial. The primary task was to count the number of pulses in one orientation while ignoring the other. Also present in the display were groups of non-overlapping lines arranged in an annulus at 4.5° eccentricity. Half of these groups were tilted leftwards and half rightwards, and, independently, half were red and half green. Once per trial, a randomly selected peripheral group pulsed in luminance, and the observers' secondary task was to report its color. Importantly, that group's orientation was not correlated with the orientation of the central target. Results: Performance in the secondary task was better when the peripheral target's orientation matched the orientation attended at fixation. Thus, heightened sensitivity to the attended orientation spread to peripheral locations where observers were not instructed to selectively attend and where doing so conferred no advantage. This new paradigm also allows us to investigate the spatial and temporal limits of the involuntary spread of FBA
National Institute of Health Research Grant RO1 EY016200.