General and Experimental Psychology, Ludwig-Maximilians-University, Leopoldstr. 13, 80802 Munich, Germany.
Neuropsychologia. 2009 Dec;47(14):3255-64. doi: 10.1016/j.neuropsychologia.2009.08.004. Epub 2009 Aug 12.
Low levels of intrinsic alertness are associated with lateralized performance in visual tasks, similar to neglect of the left (ipsilesional) visual hemi-field. However, it is unclear whether reduced alertness produces a specific lateralization of spatial-attentional processes in terms of the prioritization of right- over left-side stimuli, or whether it affects more basic functions of visuo-sensory coding, and/or higher function of the top-down control of selection, of stimuli on the left side. To decide between these alternatives, the present study examined the effects of lowered alertness, induced by a 50-min vigilance task, in a partial-report paradigm of briefly presented letter displays. With only one (unilateral) stimulus in display, no specific hemi-field effects were found under low-alertness conditions, indicating that reduced alertness impairs neither sensory effectiveness nor the top-town control of selection. However, with dual, bilateral stimuli, report accuracy was specifically affected for left-side targets (in subjects who showed comparable performance for both sides under normal-alertness conditions). This pattern can be interpreted in terms of a specific bias in spatial-attentional weighting, where prioritization of stimuli on the right leads to (mild) extinction of targets on the left. Moreover, participants who had a lower general level of alertness also showed a more pronounced re-distribution of weights, evidenced by a more severe imbalance in report accuracy, in a low compared to a normal state of alertness. This suggests that a low general level of intrinsic alertness engenders a specific vulnerability to neglect-like performance with a (mild) left-side extinction.
低水平的内在警觉性与视觉任务的侧化表现有关，类似于对左侧（同侧）视觉半视野的忽视。然而，目前尚不清楚警觉性降低是否会导致空间注意过程的特定侧化，即优先处理右侧刺激而不是左侧刺激，或者它是否会影响更基本的视感觉编码功能，以及/或者对左侧刺激的自上而下选择的更高功能。为了在这些选择之间做出决定，本研究在短暂呈现字母显示的部分报告范式中，检查了降低警觉性（通过 50 分钟的警戒任务引起）的影响。在低警觉性条件下，只有一个（单侧）刺激在显示中，没有发现特定的半视野效应，表明降低警觉性既不会损害感觉效果，也不会损害自上而下的选择控制。然而，对于双侧的双边刺激，报告准确性仅受到左侧目标的影响（在正常警觉性条件下，对两侧表现相当的受试者中）。这种模式可以根据空间注意权重的特定偏差来解释，其中对右侧刺激的优先处理导致左侧目标的（轻度）消失。此外，警觉性水平较低的参与者在低警觉性状态下，与正常警觉性状态相比，报告准确性的不平衡更为严重，表明一般警觉性水平较低会导致类似忽视的表现出现特定的脆弱性，即（轻度）左侧消失。
