Centre for Cognitive Neuroimaging, Institute of Neuroscience and Psychology, University of Glasgow, Glasgow, United Kingdom.
Cortex. 2013 Mar;49(3):827-36. doi: 10.1016/j.cortex.2011.12.007. Epub 2012 Jan 3.
Systematic biases in spatial attention are a common finding. In the general population, a systematic leftward bias is typically observed (pseudoneglect), possibly as a consequence of right hemisphere dominance for visuospatial attention. However, this leftward bias can cross-over to a systematic rightward bias with changes in stimulus and state factors (such as line length and arousal). The processes governing these changes are still unknown. Here we tested models of spatial attention as to their ability to account for these effects. To this end, we experimentally manipulated both stimulus and state factors, while healthy participants performed a computerized version of a landmark task. State was manipulated by time-on-task (>1 h) leading to increased fatigue and a reliable left- to rightward shift in spatial bias. Stimulus was manipulated by presenting either long or short lines which was associated with a shift of subjective midpoint from a reliable leftward bias for long to a more rightward bias for short lines. Importantly, we found time-on-task and line length effects to be additive suggesting a common denominator for line bisection across all conditions, which is in disagreement with models that assume that bisection decisions in long and short lines are governed by distinct processes (Magnitude estimation vs Global/local distinction). Our findings emphasize the dynamic rather than static nature of spatial biases in midline judgement. They are best captured by theories of spatial attention positing that spatial bias is flexibly modulated, and subject to inter-hemispheric balance which can change over time or conditions to accommodate task demands or reflect fatigue.
空间注意的系统偏差是一个常见的发现。在普通人群中，通常观察到系统的左偏（假性忽视），这可能是右半球对视觉空间注意占优势的结果。然而，这种左偏可以随着刺激和状态因素（如线条长度和觉醒）的变化而转变为系统的右偏。控制这些变化的过程尚不清楚。在这里，我们测试了空间注意模型，以评估它们解释这些效应的能力。为此，我们实验性地操纵了刺激和状态因素，同时健康参与者执行了地标任务的计算机版本。通过任务时间（>1 小时）来操纵状态，导致疲劳增加和空间偏差可靠地从左向右转移。通过呈现长或短的线来操纵刺激，这与主观中点从长线可靠的左偏到短线更右偏的转移有关。重要的是，我们发现任务时间和线长效应是相加的，这表明在所有条件下，线二分法有一个共同的因素，这与假设长线和短线的二分法决策由不同的过程（幅度估计与全局/局部区分）来控制的模型不一致。我们的发现强调了中线判断中空间偏差的动态而非静态性质。它们最好由空间注意理论来解释，该理论假设空间偏差是灵活调节的，并受到半球间平衡的影响，这种平衡可以随着时间或条件的变化而变化，以适应任务需求或反映疲劳。
