Poster D12, Monday, March 27, 8:00 – 10:00 am, Pacific Concourse
Sensory Activation as A Common Mechanism of Perceptual Pseudoneglect: Establishing Convergent and Discriminant Validity of Measures of Attention and Awareness
Jiaqing Chen1, Matthias Niemeier1,2; 1University of Toronto Scarborough, 2Centre for Vision Research, York University
Present knowledge of attention and awareness centers 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 in other forms of pseudoneglect. We measured biases using three perceptual tasks that require judgments about size, luminance and spatial frequency, as well as two visual search tasks that permitted serial and parallel search or parallel search alone. In each task we superimposed stimuli with different amounts of noisy pixels, 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 cross-over effect in the landmark task. In contrast, biases during visual searches were not influenced by noise. Our data are the first to demonstrate that different measures of perceptual pseudoneglect share a common mechanism of sensory activation. We argue that this mechanism feeds into specific, right-dominant processes of global awareness involved in comparisons across a wider range of the visual field.
Topic Area: ATTENTION: Spatial