Department of Psychology, University of Toronto, Toronto, Ontario, Canada.
Centre for Vision Research, York University, Toronto, Ontario, Canada.
PLoS One. 2019 Mar 7;14(3):e0212998. doi: 10.1371/journal.pone.0212998. eCollection 2019.
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.
目前对注意力和意识中心的认识集中在右脑损伤患者的缺陷上，这些患者表现出对左侧的严重忽视，称为空间忽视。然而，忽视中失去的功能还没有被很好地理解。在健康人中，他们可能会产生“假性忽视”——在各种测试中发现的对左侧的微妙偏见，这些偏见可以补充忽视中左侧的缺陷。但假性忽视的测量结果相关性很差。因此，目前还不清楚它们是否除了忽视测试的明显表面特征之外还反映了其他任何东西。为了探究一个共同的机制，我们在这里询问了视觉噪声是否会对光栅尺度任务中的左偏产生类似的影响，以及它对其他假性忽视测量是否有类似的影响。我们使用三种需要对大小（地标任务）、亮度（灰度任务）和空间频率（光栅尺度任务）进行判断的感知任务，以及两种允许串行和并行搜索或仅并行搜索的视觉搜索任务来测量偏见。在每个任务中，我们随机选择刺激的像素并将其设置为随机亮度值，就像一个较差的电视信号一样。我们发现，随着噪声水平的增加，参与者对感知判断的左偏程度越大，无论任务如何。此外，噪声放大了地标任务中长和短线条之间的差异。相比之下，视觉搜索期间的偏见不受噪声影响。我们的数据提供了至关重要的证据，表明不同的感知假性忽视测量，但不是探索性假性忽视，共享一个共同的机制。可以推测，这个共同的机制会影响到特定的、右优势的全局意识过程，这些过程涉及到两个半球之间的视觉信息整合。
