Visual field meridians modulate the reallocation of object-based attention

Abstract

Object-based attention (OBA) enhances processing within the boundaries of a selected object. Larger OBA effects have been observed for horizontal compared to vertical rectangles, which were eliminated when controlling for attention shifts across the visual field meridians. We aimed to elucidate the modulatory role of the meridians on OBA. We hypothesized that the contralateral organization of visual cortex accounts for these differences in OBA prioritization. Participants viewed BL^-shaped objects and, following a peripheral cue at the object vertex, detected the presence of a target at the cued location (valid), or at a non-cued location (invalid) offset either horizontally or vertically. In Experiment 1, the single displayed object contained components crossing both meridians. In Experiment 2, one cued object and one non-cued object were displayed such that both crossed the meridians. In Experiment 3, one cued object was sequestered into one screen quadrant, with its vertex either near or far from fixation. Results from Experiments 1 and 2 revealed a horizontal shift advantage (faster RTs for horizontal shifts across the vertical meridian compared to vertical shifts across the horizontal meridian), regardless of whether shifts take place within a cued object (Experiment 1) or between objects (Experiment 2). Results from Experiment 3 revealed no difference between horizontal and vertical shifts for objects that were positioned far from fixation, although the horizontal shift advantage reappeared for objects near fixation. These findings suggest a critical modulatory role of visual field meridians in the efficiency of reorienting object-based attention.

Target–object integration, attention distribution, and object orientation interactively modulate object-based selection

“…We interpreted these modulations of space-and object-based attention as evidence of a meridian effect, which emerges due to anisotropies in the cortical representations when spatial attention is oriented endogenously (e.g., Klein & Pontefract, 1991). We refer the reader to a detailed exploration of the meridian effect in the context of object-based attention in the present issue of this journal (Barnas & Greenberg, 2016). Third, and in confirmation of this hypothesis, we found that the effects of object orientation on space-and object-based selection are ameliorated when participants shift attention purely exogenously (Exp.…”

“…Importantly, this result indicates that the same-object cost emerging in the vertical orientation is not a reflection of a lack of object-based selection of vertical objects per se. Instead, our analysis shows that this same-object cost appears because the efficiency of attention allocation is affected when crossing the visual-field meridians (for a more detailed exploration of this issue, see Barnas & Greenberg, 2016). Given that these findings emerged under conditions of wide attention allocation prior to target onset, it is pertinent to ask: What advantage is afforded by focusing attention narrowly prior to target onset?…”

An advantage for targets located horizontally to the cued location

“…However, when the horizontal advantage is pitted against the objectbased effect, as when the objects are oriented vertically, then not only do they fail to observe an object-based effect, they observe the opposite consistent with a pure horizontal advantage. Barnas & Greenberg (2016) describe a similar horizontal advantage in their object-based task that cannot be attributed to the HVA. Their task was similar to that of Pilz et al (2012), except that their "objects" were two grey rectangles put together to form an 'L'.…”

“…In a second experiment, Barnas & Greenberg showed that this horizontal advantage persisted even when the cue and target appeared on different objects. In other words, both Pilz et al 2012 andBarnas &Greenberg, 2016 show an advantage for targets appearing horizontally (as opposed to vertically) to a cue regardless of whether the cue and target appear on the same object or different objects. Both results were interpreted as evidence that attention can move more easily along a horizontally oriented object than a vertical one, but this would not explain why attention seems to move more easily in a horizontal direction even when that means jumping from one object to another (Pilz et al, 2016).…”

“…These results come from the object-based cueing literature. There are now two papers (Barnas & Greenberg, 2016;Pilz et al, 2012) demonstrating a horizontal benefit to cueing, although both, interpret this horizontal advantage to the object-based component of cueing, despite the fact that the horizontal advantage persists whether or not the horizontally located target appears on the same object or not. Importantly, in these experiments, horizontalness and verticalness do not coincide with the horizontal meridians.…”