Related but different: Examining pseudoneglect in audition, touch and vision

The Role of Binocular Vision in Driving Pseudoneglect in Visual and Haptic Bisection: Evidence From Strabismic and Monocular Blind Individuals

Prior studies have shown that strabismic amblyopes do not exhibit pseudoneglect in visual line bisection, suggesting that the right-hemisphere dominance in the control of spatial attention may depend on a normally developing binocular vision. In this study, we aimed to investigate whether an abnormal binocular childhood experience also affects spatial attention in the haptic modality, thus reflecting a supramodal effect. To this aim, we compared the performance of normally sighted, strabismic and early monocular blind participants in a visual and a haptic line bisection task. In visual line bisection, strabismic individuals tended to err to the right of the veridical midpoint, in contrast with normally sighted participants who showed pseudoneglect. Monocular blind participants exhibited high variability in their visual performance, with a tendency to bisect toward the direction of the functioning eye. In turn, in haptic bisection, all participants consistently erred towards the left of the veridical midpoint. Taken together, our findings support the view that pseudoneglect in the visual and haptic modality relies on different functional and neural mechanisms.

Evidence for a common mechanism of spatial attention and visual awareness: Towards construct validity of pseudoneglect

Present knowledge of attention and awareness centres on deficits in patients with right brain damage who show severe forms of inattention to the left, called spatial neglect. Yet the functions that are lost in neglect are poorly understood. In healthy people, they might produce “pseudoneglect”—subtle biases to the left found in various tests that could complement the leftward deficits in neglect. But pseudoneglect measures are poorly correlated. Thus, it is unclear whether they reflect anything but distinct surface features of the tests. To probe for a common mechanism, here we asked whether visual noise, known to increase leftward biases in the grating-scales task, has comparable effects on other measures of pseudoneglect. We measured biases using three perceptual tasks that require judgments about size (landmark task), luminance (greyscales task) and spatial frequency (grating-scales task), as well as two visual search tasks that permitted serial and parallel search or parallel search alone. In each task, we randomly selected pixels of the stimuli and set them to random luminance values, much like a poor TV signal. We found that participants biased their perceptual judgments more to the left with increasing levels of noise, regardless of task. Also, noise amplified the difference between long and short lines in the landmark task. In contrast, biases during visual searches were not influenced by noise. Our data provide crucial evidence that different measures of perceptual pseudoneglect, but not exploratory pseudoneglect, share a common mechanism. It can be speculated that this common mechanism feeds into specific, right-dominant processes of global awareness involved in the integration of visual information across the two hemispheres.