Department of Neurology, University of Lübeck, Lübeck, Germany.
Neuropsychologia. 2012 Aug;50(10):2415-25. doi: 10.1016/j.neuropsychologia.2012.06.012. Epub 2012 Jun 26.
Patients with hemispatial neglect are severely impaired in orienting their attention to contralesional hemispace. Although motion is one of the strongest attentional cues in humans, it is still unknown how neglect patients visually explore their moving real-world environment. We therefore recorded eye movements at bedside in 19 patients with hemispatial neglect following acute right hemisphere stroke, 14 right-brain damaged patients without neglect and 21 healthy control subjects. Videos of naturalistic real-world scenes were presented first in a free viewing condition together with static images, and subsequently in a visual search condition. We analyzed number and amplitude of saccades, fixation durations and horizontal fixation distributions. Novel computational tools allowed us to assess the impact of different scene features (static and dynamic contrast, colour, brightness) on patients' gaze. Independent of the different stimulus conditions, neglect patients showed decreased numbers of fixations in contralesional hemispace (ipsilesional fixation bias) and increased fixation durations in ipsilesional hemispace (disengagement deficit). However, in videos left-hemifield fixations of neglect patients landed on regions with particularly high dynamic contrast. Furthermore, dynamic scenes with few salient objects led to a significant reduction of the pathological ipsilesional fixation bias. In visual search, moving targets in the neglected hemifield were more frequently detected than stationary ones. The top-down influence (search instruction) could neither reduce the ipsilesional fixation bias nor the impact of bottom-up features. Our results provide evidence for a strong impact of dynamic bottom-up features on neglect patients' scanning behaviour. They support the neglect model of an attentional priority map in the brain being imbalanced towards ipsilesional hemispace, which can be counterbalanced by strong contralateral motion cues. Taking into account the lack of top-down control in neglect patients, bottom-up stimulation with moving real-world stimuli may be a promising candidate for future neglect rehabilitation schemes.
患者有半空间忽略严重受损的注意力投向对侧半空间。虽然运动是人类最强的注意力线索之一，但仍不清楚忽视患者如何视觉探索他们的移动现实世界环境。因此，我们记录了在床边 19 例半空间忽略患者的眼球运动后，急性右半球中风，14 例右脑损伤患者无忽视和 21 例健康对照组。自然真实场景的视频首先在自由观看条件下与静态图像一起呈现，然后在视觉搜索条件下呈现。我们分析了扫视的数量和幅度、注视持续时间和水平注视分布。新的计算工具使我们能够评估不同场景特征（静态和动态对比度、颜色、亮度）对患者注视的影响。独立于不同的刺激条件，忽视患者在对侧半空间（同侧注视偏差）的注视次数减少，同侧半空间的注视持续时间增加（脱离缺陷）。然而，在视频中，忽视患者的左视野注视点落在动态对比度特别高的区域。此外，具有较少显著物体的动态场景导致明显减少病理性同侧注视偏差。在视觉搜索中，被忽视视野中的移动目标比静止目标更容易被发现。自上而下的影响（搜索指令）既不能减少同侧注视偏差，也不能影响自下而上的特征。我们的结果为动态自下而上的特征对忽视患者的扫描行为有强烈影响提供了证据。它们支持大脑注意力优先图不平衡地朝向同侧半空间的忽视模型，这种不平衡可以通过强烈的对侧运动线索来平衡。考虑到忽视患者缺乏自上而下的控制，用移动的真实世界刺激进行自下而上的刺激可能是未来忽视康复方案的一个有前途的候选方案。
